A nitrogen-containing heterocyclic hyperbranched acrylate cleaning dispersant for wafer processing and a preparation method and application thereof

Abstract

This invention belongs to the field of semiconductor manufacturing and microelectronic chemicals technology, and relates to a nitrogen-containing heterocyclic hyperbranched acrylate cleaning dispersant for wafer fabrication processes, its preparation method, and its application. The dispersant is a hyperbranched polymer with the general formula Core-[P(MA)-Linker-NHet], where Core is the hyperbranched core, P(MA) is the poly(meth)acrylate branch, Linker is the connecting arm, and NHet is the nitrogen-containing heterocyclic functional group. The preparation method employs a combination of "core-first, arm-later" atom transfer radical polymerization or reversible addition-fragmentation chain transfer polymerization with click chemistry. This dispersant is applied to wafer wet cleaning solutions, and the cleaning method includes treating the wafer with a cleaning solution containing this dispersant. This invention's dispersant, through its unique molecular structure design, improves cleaning efficiency, exhibits excellent pattern protection and low damage, superior process compatibility, and high cleanliness, providing an effective solution to the cleaning challenges of advanced processes.

Description

Technical Field

[0001] This invention relates to the fields of semiconductor manufacturing and microelectronic chemicals, specifically to a specialized chemical for wet cleaning and surface treatment processes in integrated circuit wafer fabrication. In particular, it relates to a poly(meth)acrylate polymeric dispersant with a hyperbranched topology and specific nitrogen-containing heterocyclic functional groups at the end of its side chains, its preparation method, and its application in improving the cleaning efficiency for nanoscale particles, metal contaminants, and organic residues while protecting the fine patterned structure of the wafer. Background Technology

[0002] In the integrated circuit manufacturing process, wafers undergo hundreds of processes, each of which may introduce contaminants such as particles, metal ions, and organic polymer residues. Wet cleaning is a key technology for removing these contaminants, and its efficiency directly determines the yield, reliability, and performance of devices. As technology nodes move to the nanoscale (e.g., 5nm and below), cleaning processes face unprecedented challenges: 1. Pollutant Removal Limits: For the removal of particles smaller than 10 nm and metallic pollutants (such as Fe, Cu, Al, etc.) attached at the atomic / molecular level, traditional cleaning solutions based on surfactants and chelating agents have insufficient force and low efficiency.

[0003] 2. Risk of damage to pattern structure: Three-dimensional structures such as FinFET and GAA with high aspect ratio are extremely fragile. Physical erosion and chemical etching by cleaning agents can easily lead to loss of critical dimensions (CD), line collapse or material damage (such as erosion of high mobility channel materials SiGe and Ge).

[0004] 3. Synergistic removal of complex contaminants: Contaminants in modern processes often exist in complex forms (such as metal particles wrapped in organic residues), requiring cleaning agents to act on multiple contaminants simultaneously.

[0005] 4. Cleaning agent residue problem: Traditional linear polymer or small molecule cleaning agents may be adsorbed and remain on the sidewalls or dead corners of the pattern, forming defects that are difficult to remove after subsequent heat treatment. Existing wafer cleaning additives are mostly small-molecule chelating agents (such as EDTA and hydroxylamine) or linear polymers. They have the following limitations: * Limited steric hindrance results in insufficient ability to disperse and stabilize nanoparticles.

[0006] * Its interaction mode with wafer surfaces (SiO2, SiN, metal) is limited, and its cleaning efficiency reaches a bottleneck under ultra-high cleanliness requirements.

[0007] * Linear polymers tend to entangle and adsorb within patterned structures, resulting in a high risk of residue after cleaning.

[0008] Therefore, there is an urgent need to develop a novel polymeric dispersant with an innovative molecular structure that can achieve efficient, low-damage, and residue-free cleaning. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a polymeric cleaning and dispersant based on the synergistic design of a "hyperbranched acrylate skeleton" and "multi-functional nitrogen-containing heterocyclic terminals". This design aims to provide strong steric hindrance and anti-adsorption properties through the three-dimensional molecular structure, and to achieve multi-mode, high-intensity, and tunable interactions with different pollutants through multiple nitrogen-containing heterocyclic functional groups at the terminals, thereby breaking through the efficiency and safety boundaries of current cleaning technologies. To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a nitrogen-containing heterocyclic hyperbranched acrylate dispersant for wafer cleaning, characterized in that it is a hyperbranched polymer having the general formula shown in formula (I): Core-[P(MA)-Linker-NHet] (I) in: The core is a hyperbranched nucleus, preferably a pentaerythritol, trimethylolpropane, or cyclodextrin-derived polyhydroxy or polyamine initiating nucleus. This core provides the starting point for the three-dimensional growth of the molecule.

[0010] P(MA) consists of poly(meth)acrylate branches, formed by controlled free radical polymerization of (meth)acrylate monomers initiated from the core, constituting the backbone of the hyperbranched structure. These branches endow the molecule with good solubility (in alkaline or semi-aqueous cleaning solutions) and nanoscale hydrodynamic dimensions.

[0011] The linker is a connecting arm selected from flexible polyethylene glycol chains (PEG, Mn=100-400), alkyl chains (C2-C6), or short chains containing ester / amide groups. It is used to adjust the degree of freedom of movement of the terminal functional groups and their distance from the trunk, optimizing its spatial matching with the surface of contaminants.

[0012] NHet is a nitrogen-containing heterocyclic functional group that is covalently linked to the end of the linker and is selected from one or more of the following combinations: a) Imidazolium salts: such as 1-vinyl-3-alkylimidazolium salts ([ViIm][X]), whose cations can be adsorbed onto negatively charged contaminants (such as SiO2 particles, some metal oxides) and wafer surfaces through electrostatic interactions, and whose alkyl chains provide hydrophobic effects.

[0013] b) Triazole / tetraazole derivatives: such as 1,2,4-triazole-3-thiol or 5-mercapto-1-methyltetraazole. These groups are rich in nitrogen atoms and can form strong coordination bonds with a variety of metal ions (especially transition metals such as Cu⁺, Ag⁺, and Co²⁺), efficiently chelating and removing metal contaminants. Furthermore, the thiol / thionyl group can form strong chemisorption on metal surfaces.

[0014] c) Piperazine / morpholine derivatives: such as N-aminoethylpiperazine, whose secondary and tertiary amine nitrogen atoms can provide basicity and hydrogen bonding, effectively dissolving and removing organic photoresist residues and acidic contaminants.

[0015] n is the number of branches, satisfying that the number average molecular weight (Mn) of the hyperbranched polymer is 5,000 - 50,000 g / mol, the molecular weight distribution (Ð) is <1.8, and each molecule contains an average of 10 - 100 nitrogen-containing heterocyclic functional groups (NHet). Preferably, the hyperbranched polymer has excellent solubility or stable colloidal dispersion in water or alkaline aqueous solutions (such as 0.01%-2% TMAH solution), and its hydrodynamic diameter is between 2 and 15 nm.

[0016] Preferably, in the NHet functional group, the combination ratio of a) imidazolium salt and b) triazole / tetrazolium is 1:2 to 2:1 (molar ratio) to achieve particle dispersion and metal chelation through synergistic effect. Secondly, the present invention provides a method for preparing the above-mentioned hyperbranched dispersant, characterized in that it employs a route combining "core-first, arm-later" atom transfer radical polymerization (ATRP) or reversible addition-fragmentation chain transfer (RAFT) polymerization with click chemistry: Step S1: Synthesis of multifunctional ATRP / RAFT initiators Using pentaerythritol as the core, multifunctional initiators with 4 or 8 ATRP initiation sites or RAFT chain transfer sites are synthesized by reacting with 2-bromoisobutyryl bromide or trithioester RAFT reagents. Step S2: Synthesis of hyperbranched poly(meth)acrylate Using a core-initiator as the initiator and hydroxyethyl methacrylate (HEMA) or glycidyl methacrylate (GMA) as monomers, hyperbranched poly(meth)acrylates (HB-P(HEMA) or HB-P(GMA)) with numerous hydroxyl or epoxy groups at the ends are synthesized via ATRP or RAFT polymerization. The molecular weight and branch length are precisely controlled by adjusting the monomer / initiator ratio. Step S3: Click chemistry grafting of the connecting arm to a nitrogen-containing heterocyclic functional group** 1. If the product of step S2 is HB-P(HEMA), then its hydroxyl group is reacted with excess glutaric anhydride to convert it into an intermediate with a carboxyl group at the end.

[0017] 2. The above intermediate (containing carboxyl or epoxy groups) is subjected to a highly efficient click chemistry reaction with a Linker-NHet prefabricated module (prepared in advance via organic synthesis) with amino (-NH2) or azide (-N3) terminal groups: For the carboxyl intermediate, it undergoes an amidation reaction with Linker-NHet-NH2 in the presence of a condensing agent.

[0018] For HB-P(GMA), its epoxy group can directly undergo a ring-opening addition reaction with Linker-NHet-NH2.

[0019] Alternatively, an azide-alkynyl cycloaddition (CuAAC) reaction can be used to graft alkynyl-containing Linker-NHet onto azide-containing polymers.

[0020] 3. After the reaction is complete, unreacted small molecules are removed by precise purification methods such as dialysis and ultrafiltration to obtain a high-purity target hyperbranched dispersant. Thirdly, the present invention provides the application of the above-mentioned hyperbranched dispersant in wafer wet cleaning solution.

[0021] The cleaning solution contains: Main solvents: deionized water, semi-aqueous solvents (such as a mixture of DMSO, DMF and water) or alkaline aqueous solutions (containing <5% organic amines, such as TMAH).

[0022] Functional ingredient: The hyperbranched dispersant described in this invention is added at a concentration of 10-1000 ppm.

[0023] Optional additives: very low concentrations of oxidants (such as ozone), reducing agents (such as dilute HF), or other synergistic cleaning agents. Fourthly, the present invention provides a wafer cleaning method, which includes the step of treating the wafer with a cleaning solution containing the hyperbranched dispersant, wherein the treatment method includes immersion, spraying or spin spraying. The beneficial effects of this invention are: 1. **Improved cleaning efficiency:** * “Molecular brush” effect: Hyperbranched structures form a dense, highly hydrated “molecular brush” on contaminants and wafer surfaces, which powerfully strips nanoparticles through strong steric hindrance and osmotic pressure and prevents their redeposition.

[0024] * Multidentate synergistic chelation: Multiple functional groups such as triazole can simultaneously bind to a metal ion or multiple metal pollutants, forming a more thermodynamically stable and kinetically faster chelation structure, which greatly improves the metal removal rate (URR).

[0025] * Multifunctional Synergy: Different NHet functional groups can target particles, metals, and organic matter respectively, achieving "one-stop" cleaning of complex pollutants. 2. Excellent graphic protection and low damage: * The nanoscale molecular size and rigid three-dimensional structure make it difficult to embed or entangle in the narrow gaps of high aspect ratio patterns, reducing the risk of cleaning agent residue from the source.

[0026] * The molecular interaction mode is mainly based on physical spatial barrier and specific chemical interaction, which avoids the severe etching of traditional strong acids and bases. It has an excellent protective effect on sensitive materials such as SiGe, Ge, and low-k media, and the critical dimension loss (CD Loss) is minimal. 3. Excellent process compatibility and cleanliness: * The polymer design avoids the introduction of metal ions, which can be effectively removed by subsequent deionized water rinsing or heat treatment (with controllable decomposition temperature), meeting the requirements of semiconductor-grade ultra-high purity and low residue.

[0027] * Remains stable over a wide range of pH and temperature conditions, suitable for a variety of cleaning formulations (SC1, SC2, back-end cleaning, etc.). Detailed Implementation Methods and Examples Example 1: Synthesis of an imidazole / triazole bifunctional hyperbranched dispersant (HB-Im / Tri) 1. Synthesis Prefabrication Module: Synthesize a Linker (Linker-Im) with an amino group at one end and 1-ethyl-3-carboxymethylimidazolium chloride at the other end, and a Linker (Linker-Tri) with an amino group at one end and 1,2,4-triazol-3-thiol at the other end.

[0028] 2. Synthesis of hyperbranched framework: GMA polymerization was initiated by pentaerythritol tetrafunctional ATRP initiator to synthesize HB-P(GMA) with Mn≈20,000.

[0029] 3. Click grafting: HB-P(GMA) is reacted with an equimolar mixture of Linker-Im and Linker-Tri (total amino to epoxy molar ratio 1:1.1) at 60°C for 24 hours to open the epoxy ring.

[0030] 4. Purification: The reaction solution was repeatedly washed and purified through an ultrafiltration membrane with a molecular weight cutoff of 10 kDa, and then freeze-dried to obtain a white solid HB-Im / Tri. Cleaning performance test: * Test wafer: 12-inch silicon wafer with SiO2 pattern (50nm linewidth, aspect ratio 5:1) on the surface, and artificially contaminated with Cu²⁺ (5E13 atoms / cm²) and 30nm SiO2 particles.

[0031] * Cleaning solution: 0.1% TMAH aqueous solution containing 50 ppm HB-Im / Tri.

[0032] * Control solution: Commercially available linear polyelectrolyte-based cleaning agent.

[0033] * Process: Room temperature, ultrasonic-assisted cleaning (low power) for 2 minutes, rinse with deionized water, and dry with nitrogen.

[0034] * Characterization: TXRF was used to measure metal residue, SP1 was used to measure particle number, and SEM was used to measure CD loss and pattern integrity. Evaluation indicators After pollution After treatment with commercial cleaning agents After HB-Im / Tri treatment (this invention) Cu residue (atoms / cm²) 5E13 2E10 <5E9 >30nm particle count >500 25 <5 CD loss (nm) - 1.2 0.3 Graphical collapse rate - 0.5% 0% Conclusion: The hyperbranched dispersant HB-Im / Tri provided by this invention improves copper removal rate and particle removal rate by more than an order of magnitude compared with existing commercial products, while reducing critical size loss by more than 75% and completely avoiding the collapse of high aspect ratio patterns. Its comprehensive performance significantly surpasses the existing technology, providing a very promising solution for the cleaning challenges of advanced processes.

Claims

1. A hyperbranched polymer dispersant for wafer process cleaning, characterized in that, It has the structure shown in the general formula Core-[P(MA)-Linker-NHet], where Core is a multifunctional initiator core, P(MA) is a poly(meth)acrylate branch, Linker is a linker arm, and NHet is a nitrogen-containing heterocyclic functional group selected from at least one of imidazolium salts, triazoles, tetrazolium, piperazines, or morpholine derivatives, and n such that the polymer has a number-average molecular weight of 5,000-50,000 and contains an average of 10-100 NHet functional groups per molecule.

2. The dispersant according to claim 1, characterized in that, The NHet comprises a combination of an imidazolium salt group and a triazole or tetrazolium group.

3. The dispersant according to claim 1, characterized in that, The Linker is a polyethylene glycol segment, a C2-C6 alkylene chain, or a short chain containing ester / amide groups.

4. The dispersant according to any one of claims 1-3, characterized in that, Its hydrodynamic diameter in water or alkaline aqueous solution is 2-15 nm.

5. A method for preparing the dispersant according to any one of claims 1-4, characterized in that, include: (1) Controlled free radical polymerization of (meth)acrylate monomers is initiated by a multifunctional initiator to form a hyperbranched polymer backbone with reactive groups at the ends; (2) By clicking chemical reaction, a pre-synthesized linker-NHet module with a nitrogen-containing heterocyclic functional group NHet at the end is grafted onto the terminal reactive group of the skeleton.

6. The method according to claim 5, characterized in that, The controlled free radical polymerization is atom transfer radical polymerization (ATRP) or reversible addition-fragmentation chain transfer (RAFT) polymerization; the click chemistry reaction is amidation reaction, epoxy ring-opening reaction or azide-alkynyl cycloaddition reaction.

7. The use of the hyperbranched polymer dispersant as described in any one of claims 1-4 in the preparation of a wafer wet cleaning solution.

8. A wafer wet cleaning solution, characterized in that, It contains a solvent and 10-1000 ppm of the hyperbranched polymer dispersant as described in any one of claims 1-4.

9. The cleaning solution according to claim 8, characterized in that, The solvent is deionized water, a semi-aqueous solvent, or an alkaline aqueous solution.

10. A wafer cleaning method, characterized in that, The step includes cleaning the patterned wafer using the cleaning solution described in claim 8 or 9.