Semiconductor chip CMP post-cleaning agent and preparation method and application thereof

Abstract

The invention relates to a semiconductor chip CMP post-cleaning agent and a preparation method and application thereof, and the semiconductor chip CMP post-cleaning agent comprises the following components by weight: 10-30 parts of a composite functional agent; 5-20 parts of a chelating agent; 5 to 15 parts of a pH regulator; and 50-95 parts of ultrapure water. The compound functional agent has a cholesterol structure modified by a polyethylene glycol chain and biotin, so that the compound functional agent is endowed with excellent dissolvability, and the stability of the whole subsequent solution system is ensured.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing processes, and particularly relates to a post-CMP cleaning agent for semiconductor chips, its preparation method, and its application. Background Technology

[0002] Integrated circuits, as a new type of semiconductor, have become a crucial support for national economic growth and national defense due to their small size, light weight, long lifespan, low cost, high reliability, and excellent performance. They are also an important prerequisite for realizing intelligent and networked society and a significant indicator of a nation's comprehensive national strength. The development of integrated circuits is rapid, with continuous improvements in design and manufacturing levels. Feature size, as a key indicator of integrated circuit design and manufacturing capabilities, has now entered the era of very large-scale integrated circuits (GLSI). Feature size refers to the gate channel length of a semiconductor device and can also be used to represent the minimum linewidth of a process. With the continuous reduction of integrated circuit feature size, the RC delay and electromigration problems of metal interconnects are becoming increasingly prominent, leading to a continuous decrease in device reliability. Therefore, replacing Al with Cu, which has low resistivity, low dielectric constant, and low electromigration, has become a research focus for high-performance interconnect materials.

[0003] However, the fabrication of copper interconnects faces the challenge of removing excess copper. Traditional dry etching is ineffective at removing copper because its halide vapor pressure is low at room temperature, making it difficult to volatilize. To match the ever-decreasing feature sizes and increasingly sophisticated chip functions, the integrated circuit industry has placed higher technical demands on copper surface planarization. CMP, as a primary planarization technology, achieves localized and global planarization of the copper surface through the combined action of chemical and mechanical processes. Copper CMP, through the synergistic effect of chemical etching and mechanical polishing, achieves efficient and uniform copper removal and surface planarization, meeting the requirements of advanced processes. Furthermore, copper CMP is widely used in double damask processes for polishing vias and fine copper wires, improving chip performance and reliability. With the development of semiconductor technology, copper CMP technology has become an indispensable key process in chip manufacturing.

[0004] Ceramic patterning (CMP) has become the only mature and successfully applied copper patterning process in IC manufacturing. During CMP, the abrasive action breaks the chemical bonds on the wafer surface, increasing surface energy and activity. This makes the wafer surface prone to adsorbing contaminants, resulting in a large amount of residual metal ions, particles, and organic matter on the wafer surface after CMP, affecting device reliability and yield. Therefore, cleaning after CMP to remove Cu surface contaminants has become crucial for device integration and stability.

[0005] Post-CMP cleaning refers to the process of removing contaminants from the wafer surface using physical, chemical, and mechanical methods. Physical cleaning utilizes physical forces such as light, electricity, and heat to enhance the energy of the contaminants, causing them to detach from the wafer surface through vibration. Chemical methods involve reacting cleaning agents with surface contaminants to generate small molecules soluble in the cleaning agent, thereby removing the contaminants, or breaking the chemical bonds between the contaminants and the wafer surface, causing them to detach. Mechanical methods rely on friction and other mechanical forces to detach surface contaminants from the wafer surface. Mechanical cleaning can easily scratch the wafer surface, while chemical cleaning is slow.

[0006] Currently, the most common cleaning methods in CMP post-cleaning are a combination of chemical, physical, and mechanical methods. These methods include two main types: dry cleaning (laser cleaning, supercritical fluid cleaning, plasma cleaning, etc.) and wet cleaning (RCA cleaning, ultrasonic cleaning, megasonic cleaning, and brushing, etc.). RCA cleaning, in particular, removes contaminants from the wafer surface through physical dissolution or chemical action using various chemical reagents. After each cleaning cycle, the wafer surface must be rinsed with ultrapure water to prevent secondary contamination from the reagents. Chemical cleaning solutions often use APM (acetic acid-base mixture), i.e., NH4OH, H2O2, and H2O mixed in a specific ratio. This type of cleaning solution easily oxidizes and corrodes the wafer surface, increasing its roughness. Furthermore, RCA cleaning is complex, requires large amounts of chemical reagents and ultrapure water, and is extremely costly. The acidic and alkaline reagents and strong oxidants used in the cleaning solution can easily pose safety hazards during the cleaning process, and the large volume of wastewater discharged after cleaning can cause environmental problems.

[0007] In wet cleaning after CMP (Chemical Mechanical Polishing), the cleaning agent is crucial to the cleaning quality and efficiency. In the short term, significant breakthroughs in cleaning methods are unlikely, making cleaning agents a key area of ​​research and development in post-CMP cleaning. Currently, cleaning agents are categorized into acidic and alkaline agents. Traditional acidic cleaning solutions, such as SC-2, HF, or HPM, often contain highly corrosive chemicals. These chemicals are highly corrosive and toxic, easily increasing wafer surface roughness and causing environmental pollution. Especially with the continuous reduction in integrated circuit feature sizes, cobalt and ruthenium are gradually replacing tantalum as new barrier layer materials in Cu processes. Acidic cleaning solutions can react with cobalt and ruthenium to generate gases, further increasing wafer surface roughness.

[0008] Therefore, further research is needed on the mechanical, chemical, and electrochemical behavior of acidic cleaning agents on wafer surfaces to improve their corrosion resistance and ensure a smooth wafer surface after cleaning.

[0009] Therefore, to address the corrosive defects of existing cleaning agents, this invention focuses on the difference in adsorption and desorption between surface contaminants and cleaning agents. It employs a composite functional agent with a cholesterol structure modified with polyethylene glycol chains and biotin to ensure that while contaminants detach from the copper surface, the cleaning agent preferentially adsorbs onto the copper surface to form a protective layer. Furthermore, it combines a chelating agent with a supramolecular cavity structure to block the adsorption of contaminants and corrosive media, thus achieving the design concept of high-efficiency cleaning and low corrosion. Summary of the Invention

[0010] The technical problem solved by this invention is that acidic cleaning agents used after copper CMP in the prior art are prone to corroding copper, resulting in a rough copper surface.

[0011] In view of the technical problems existing in the prior art, the present invention designs a low-corrosion Cu CMP post-cleaning agent for semiconductor chips, which can maintain an excellent cleaning effect even under pure immersion process conditions and has low corrosion to copper.

[0012] It should be noted that, in this invention, unless otherwise specified, the specific meaning of "comprising" in relation to composition definition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," etc., and similar meanings.

[0013] To solve the aforementioned technical problems, the present invention adopts the following solution:

[0014] [The first technical solution]

[0015] A post-CMP cleaning agent for semiconductor chips, characterized in that it comprises the following components by weight:

[0016] 10-30 parts of compound functional agent;

[0017] Chelating agent 5-20 parts;

[0018] 5-15 parts of pH adjuster;

[0019] 50-95 parts ultrapure water;

[0020] The composite functional agent is a modified cholesterol-based organic complex.

[0021] Furthermore, the composite functional agent is a polyethylene glycol-modified cholesterol-based organic complex.

[0022] Furthermore, the composite functional agent is one or more of cholesterol-polyethylene glycol-aldehyde, cholesterol-polyethylene glycol-azide, and cholesterol-polyethylene glycol-biotin.

[0023] Furthermore, the chelating agent is a water-soluble cyclodextrin-type cyclic compound.

[0024] Furthermore, the chelating agent is one or more of methyl-β-cyclodextrin, carboxymethyl-β-cyclodextrin, and glucose-β-cyclodextrin.

[0025] Furthermore, the mass ratio of the composite functional agent to the chelating agent is (1-5):1.

[0026] Furthermore, the pH adjuster is a sulfonic acid compound.

[0027] Furthermore, the pH adjuster is one or more of N-cyclohexyl-2-aminoethanesulfonic acid, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, and 2-morpholinoethanesulfonic acid.

[0028] Furthermore, the cleaning agent used after CMP of the semiconductor chip is weakly acidic.

[0029] Furthermore, the pH of the cleaning agent after CMP of the semiconductor chip is 3.5-7.

[0030] In this invention, in order to further optimize the performance of the post-CMP cleaning agent, the components can be optimized as follows: 15-25 parts of composite functional agent; 10-15 parts of chelating agent; 5-10 parts of pH adjuster; and 70-85 parts of ultrapure water.

[0031] In this invention, the composite functional agent is preferably cholesterol-polyethylene glycol-biotin.

[0032] In this invention, the chelating agent is preferably glucose-β-cyclodextrin.

[0033] In this invention, the pH adjuster is preferably 2-morpholinoethanesulfonic acid.

[0034] In this invention, the pH of the cleaning agent after CMP of the semiconductor chip is preferably 4.5-6.5.

[0035] In this invention, the composite functional agent in the post-CMP cleaning agent for semiconductor chips plays a unique role:

[0036] Firstly, the composite functional agent of this invention uses a polyethylene glycol-modified cholesterol-based organic complex. Different groups are added to the cholesterol-polyethylene glycol matrix, resulting in multiple functions including cleaning, corrosion inhibition, and stabilization. The cholesterol and biotin groups in this composite functional agent can interact with the copper surface, facilitating the formation of a passivation film on the chip surface. This film exhibits good film stability, reduces contact between the copper surface and corrosive media, and inhibits oxide film formation, thereby achieving the effect of inhibiting metal corrosion.

[0037] Secondly, this composite functional agent 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 and soluble complex, and be carried away from the chip surface by the flowing cleaning agent, thus achieving a good cleaning effect.

[0038] Third, the polyethylene glycol chain contained in this composite functional agent greatly enhances its hydrophilicity and water solubility, thereby increasing the stability of the subsequent solution system. This allows it to easily penetrate between the contaminant particles adhering to the chip and its surface, causing the particles attached to the chip surface to fall off and further preferentially adsorb onto the fresh copper surface to form a protective layer, preventing secondary adsorption of contaminants and keeping the chip surface easy to clean for a long time.

[0039] In this invention, the chelating agent in the post-CMP cleaning agent for semiconductor chips plays a unique role:

[0040] Firstly, the unique supramolecular cavity structure of this chelating agent has amphiphilic properties. Its outer wall is hydrophilic, while the cavity interior is a hydrophobic environment. This increases its own conjugation and allows it to form hydrogen bonds with itself and other molecules, further increasing the thermal stability and solubility of the cleaning agent system.

[0041] Secondly, the hydrophobic cavity of the material gives it the framework of a supramolecular metal coordination compound, which can dissolve the oxide film generated on the chip surface and then form coordination bonds with copper atoms, thereby promoting the chemical adsorption of the cleaning agent on the copper surface to slow down corrosion.

[0042] Third, chelating agents can be used in conjunction with composite functional agents. Through the inclusion of cholesterol groups by the hydrophobic cavity and the hydrogen bonding of the composite functional agent by the hydrophilic outer wall, the permeability and adhesion of the agent on the chip surface are increased, thus isolating corrosive media and contaminant particles and further improving the cleaning effect. At the same time, it avoids the re-adhesion of residues on the chip surface, which would cause secondary pollution.

[0043] In this invention, the pH adjuster in the post-CMP cleaning agent for semiconductor chips plays a unique role:

[0044] This pH adjuster can adjust the cleaning agent system to a weakly acidic environment. At the same time, the morpholine and sulfonic acid groups it contains can inhibit the formation of metal oxides, chelate residual metal ions on the surface, remove them from the copper surface with the solution, and promote the formation of a passivation film, thus avoiding direct contact between the corrosive medium and the copper surface and inhibiting metal corrosion.

[0045] [Second Technical Solution]

[0046] A method for preparing the above-mentioned post-CMP cleaning agent for semiconductor chips includes the following steps:

[0047] Step 1: Weigh out the respective amounts of each component;

[0048] Step 2: Add all components except pure water to the container and stir until all materials are completely dissolved. Finally, add pure water to obtain the semiconductor chip CMP post-cleaning agent.

[0049] [The third technical solution]

[0050] A method for using the above-mentioned post-CMP cleaning agent for semiconductor chips includes the following steps:

[0051] Step 1: Prepare an aqueous solution with a mass percentage concentration of 10-100% using ultrapure water after CMP cleaning of the semiconductor chip. Then, use this aqueous solution to soak the semiconductor chip at room temperature for 5-30 minutes to obtain the soaked semiconductor chip.

[0052] Step 2: Rinse the soaked semiconductor chip in ultrapure water at least twice to complete the cleaning process of the semiconductor chip.

[0053] [Fourth technical solution]

[0054] The use of the above-mentioned post-CMP cleaning agent for cleaning semiconductor chips.

[0055] This invention provides a post-CMP cleaning agent for semiconductor chips, its preparation method, and its application, which have the following beneficial effects:

[0056] 1. The composite functional agent used in this invention has a polyethylene glycol chain and a biotin-modified cholesterol structure, which endows it with excellent solubility and ensures the stability of the entire solution system. Its coordination with metal ions accelerates the dissolution of the oxide layer on the copper surface and forms stable and soluble complexes with the metal ions in the solution system, allowing contaminants to detach from the copper surface. Simultaneously, this composite functional agent preferentially adsorbs onto the copper surface to form a protective layer, preventing the re-formation of the oxide film and avoiding contact between corrosive media and contaminant particles and the copper surface, thus preventing secondary pollution.

[0057] 2. The chelating agent used in this invention has a supramolecular cavity structure, which can form inclusion complexes with composite functional agents, increasing the stability and solubility of the solution system, achieving rapid dissolution of metal oxides, while inhibiting uneven corrosion of the substrate by corrosive media, ensuring that the copper surface is smooth and has low corrosion after cleaning.

[0058] 3. After the components are mixed, the cleaning agent can generate intermolecular interaction forces, and after mutual dissolution and promotion, the solubility and stability of each other are further improved and enhanced.

[0059] Therefore, the cleaning agent of the present invention has very good application prospects and potential for large-scale industrial promotion in the field of semiconductor chip cleaning. Attached Figure Description

[0060] Figure 1 : A microscope image of a Cu wafer before cleaning, magnified 100 times;

[0061] Figure 2 : A microscope image magnified 100 times after cleaning a Cu wafer with the cleaning agent of Example 1 of the present invention;

[0062] Figure 3 : A microscope image magnified 100 times after cleaning a Cu wafer with the cleaning agent of Comparative Example 1 of this invention. Detailed Implementation

[0063] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0064] In this invention, Examples 1-6 and Comparative Examples 1-5 disclose a variety of cleaning agents, the components and their mass ratios of which are shown in Tables 1 and 2.

[0065] Table 1. Components and proportions of cleaning agents for semiconductor chips after CMP in Examples 1-6

[0066] Table 2. Components and proportions of cleaning agents for semiconductor chips after CMP in Comparative Examples 1-5

[0067] The preparation method of the cleaning agent for CMP of the semiconductor chip of the present invention is as follows:

[0068] Step 1: Weigh out the respective amounts of each component;

[0069] Step 2: Add all components except pure water to the container and stir until all materials are completely dissolved. Finally, add pure water to obtain the semiconductor chip CMP post-cleaning agent. The pH of the semiconductor chip CMP post-cleaning agent is 3.5-7.

[0070] Instructions for using the cleaning agent after CMP of the semiconductor chip according to this invention:

[0071] Step 1: Prepare an aqueous solution with a mass percentage concentration of 10%-100% using ultrapure water after CMP cleaning of the semiconductor chip. Then, use this aqueous solution to soak the semiconductor chip at room temperature for 5-30 minutes to obtain the soaked semiconductor chip.

[0072] Step 2: Rinse the soaked semiconductor chip in ultrapure water at least twice to complete the cleaning process of the semiconductor chip.

[0073] Regarding performance testing and explanation:

[0074] Performance 1: The test method for metal corrosion is a static corrosion test.

[0075] Step 1: Cut the copper wafer into 2cm*2cm square pieces, pre-treat with 3wt% citric acid solution at room temperature for 5 minutes, wash with ultrapure water, and dry with nitrogen gas;

[0076] Step 2: Take images of the copper wafer using a microscope. (See attached image) Figure 1 The film thickness and resistivity of the copper wafer were measured using a four-probe method to determine the functional relationship between copper thickness and resistivity, which was then used to calculate the copper corrosion rate (Å / min).

[0077] Step 3: Prepare a 10% (w / w) aqueous solution of the cleaning agent with ultrapure water. Then, take 20 mL of the 10% cleaning agent aqueous solution and immerse the copper wafer in it for 5 hours at room temperature for static etching. After rinsing with ultrapure water, dry it with nitrogen.

[0078] Step 4: Take microscopic images of the etched copper wafers for comparison. (See attached image) Figure 2 and Figure 3 The thickness of the copper wafer after corrosion was measured using a four-probe tester. The corrosion rate was then calculated based on the change in the thickness of the copper wafer before and after corrosion, thus examining the corrosion of the metal by different cleaning agents. The test results are shown in Table 3.

[0079] The performance test results of the cleaning agents obtained in Examples 1-6 and Comparative Examples 1-5 are shown in Table 3.

[0080] Table 3 Test Data

[0081] Analysis and explanation of the test results:

[0082] As can be seen from the test data in Table 3, the cleaning agent of the present invention has a lower corrosion rate on copper and a better cleaning effect. In contrast, Comparative Example 1, lacking a composite functional agent, resulted in more severe corrosion of copper. Comparative Example 2, lacking a chelating agent, had a reduced ability to bind metal ions, leading to a worse cleaning and corrosion inhibition effect. Comparative Example 3, using polyethylene glycol as a composite functional agent, resulted in a worse corrosion inhibition effect. Comparative Example 4, using biotin as a composite functional agent, resulted in a worse corrosion inhibition effect. Comparative Example 5, using β-cyclodextrin as a chelating agent, resulted in a worse corrosion inhibition effect.

[0083] Further comparison can be made using the accompanying diagrams in the instruction manual:

[0084] Figure 1 A microscope image of a Cu wafer before cleaning, magnified 100 times. Figure 2A microscope image magnified 100x after cleaning a Cu wafer with the cleaning agent of Example 1 of the present invention; Figure 3 This is a microscope image magnified 100 times after cleaning a Cu wafer with the cleaning agent of Comparative Example 1 of this invention.

[0085] from Figure 2 As can be seen, the cleaning agent used in Example 1 caused almost no corrosion after treatment. Figure 3 As can be seen, the surface treated with the cleaning agent in Comparative Example 1 was rough and severely corroded.

[0086] The present invention has been described above by way of example with reference to the embodiments and accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A post-CMP cleaning agent for semiconductor chips, characterized in that, Based on parts by weight, it includes the following components: 10-30 parts of compound functional agent; Chelating agent 5-20 parts; 5-15 parts of pH adjuster; 50-95 parts ultrapure water; The composite functional agent is a modified cholesterol-based organic complex.

2. The semiconductor chip CMP post-cleaning agent according to claim 1, characterized in that: The composite functional agent is one or more of cholesterol-polyethylene glycol-aldehyde, cholesterol-polyethylene glycol-azide, and cholesterol-polyethylene glycol-biotin.

3. The semiconductor chip CMP post-cleaning agent according to claim 1, characterized in that: The chelating agent is a water-soluble cyclodextrin-type cyclic compound.

4. The semiconductor chip CMP post-cleaning agent according to claim 1 or 3, characterized in that: The chelating agent is one or more of methyl-β-cyclodextrin, carboxymethyl-β-cyclodextrin, and glucose-β-cyclodextrin.

5. The semiconductor chip CMP post-cleaning agent according to claim 1, characterized in that: The pH adjuster is a sulfonic acid compound.

6. The semiconductor chip CMP post-cleaning agent according to claim 1 or 5, characterized in that: The pH adjuster is one or more of N-cyclohexyl-2-aminoethanesulfonic acid, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid, and 2-morpholinoethanesulfonic acid.

7. The semiconductor chip CMP post-cleaning agent according to claim 1, characterized in that: The cleaning agent used after CMP of the semiconductor chip is weakly acidic.

8. A method for preparing a post-CMP cleaning agent for semiconductor chips according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Weigh out the respective amounts of each component; Step 2: Add all components except ultrapure water to the container and stir until all materials are completely dissolved. Finally, add ultrapure water to obtain the semiconductor chip CMP post-cleaning agent.

9. A method of using the semiconductor chip CMP post-cleaning agent according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Prepare an aqueous solution with a mass percentage concentration of 10-100% using ultrapure water after CMP cleaning of the semiconductor chip. Then, use this aqueous solution to soak the semiconductor chip at room temperature for 5-30 minutes to obtain the soaked semiconductor chip. Step 2: Rinse the soaked semiconductor chip in ultrapure water at least twice to complete the cleaning process of the semiconductor chip.

10. The use of the semiconductor chip post-CMP cleaning agent according to any one of claims 1-7 in cleaning semiconductor chips.

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