Chemical mechanical polishing solution for rhodium interconnect layer and preparation method and application thereof

Abstract

The application provides a chemical mechanical polishing liquid for rhodium interconnection layer and a preparation method and application thereof, and comprises the following components in percentage by weight: 0.05wt%-0.30wt% of surface functionalized nanodiamond abrasive, 0.50wt%-3.00wt% of oxidizing agent, 0.20wt%-1.50wt% of complexing agent, 0.001wt%-0.010wt% of selective control agent, and pH regulator. The application adds polyaspartic acid or alkali metal salt thereof as the selective control agent in the polishing liquid, so that the selective control agent has a preferential adsorption and protection effect on the surface of the non-target layer, thereby reducing the risk of excessive removal of the medium layer and related barrier / liner layer. Meanwhile, the overall pH of the polishing liquid is controlled in the alkaline range of 9.5-10.5, and the main liquid and the oxidizing agent are stored separately and mixed before use, which is beneficial to the long-term stability of the polishing liquid and the interface reaction activity during use.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing (CMP) technology for semiconductor materials, and particularly to a CMP slurry for rhodium interconnect layers, its preparation method, and its application. Background Technology

[0002] As integrated circuit feature sizes continue to shrink to 5 nanometers and below, traditional copper interconnect technology is struggling to meet performance requirements due to a sharp increase in resistivity and a significant deterioration in electromigration reliability. Rhodium, with its excellent resistivity at the nanoscale, extremely high intrinsic electromigration resistance (expected lifetime can be tens of times longer than copper), and potential as a self-blocking layer, is considered a key candidate material for next-generation interconnect metals.

[0003] However, integrating rhodium into existing semiconductor manufacturing processes, particularly the chemical mechanical polishing (CMP) step, faces three major technological bottlenecks: (1) Difficult to remove chemically: Rhodium is extremely inert in chemical properties. The rhodium oxide (Rh2O3) passivation layer formed on its surface is dense and stable, which makes the chemical action of polishing liquid based on conventional oxidants (such as hydrogen peroxide) and complexing agents weak and the removal rate extremely low.

[0004] (2) Mechanical polishing is challenging: Rhodium has high hardness and high toughness, which is difficult to remove efficiently by traditional silicon dioxide or alumina abrasives. Furthermore, it is very easy to cause severe surface scratches, residual particles and subsurface damage due to mismatch in abrasive hardness or agglomeration, which cannot meet the requirements of advanced processes for atomically smooth surfaces.

[0005] (3) Stringent polishing selectivity requirements: When polishing patterned wafers, an extremely high polishing selectivity (usually >100:1) must be achieved for the underlying ultra-low k dielectric layer (dielectric constant k<2.5) and the sidewall / bottom barrier / liner layer (such as tantalum, ruthenium, cobalt) to strictly control dish-shaped depressions and erosion, and to ensure the electrical performance and reliability of the interconnect structure. To this end, a chemical mechanical polishing slurry for rhodium interconnect layers is proposed, along with its preparation method and application. Summary of the Invention

[0006] In view of this, the present invention provides a chemical mechanical polishing slurry for rhodium interconnect layers, a method for preparing the slurry, and its application, to solve or alleviate the technical problems existing in the prior art, and at least provide a beneficial alternative.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a chemical mechanical polishing (CMP) slurry for rhodium interconnect layers. The CMP slurry, by weight percentage, comprises 0.05 wt% to 0.30 wt% surface-functionalized nanodiamond abrasive, 0.50 wt% to 3.00 wt% oxidant, 0.20 wt% to 1.50 wt% complexing agent, 0.001 wt% to 0.010 wt% selectivity control agent, a pH adjuster, and the balance being deionized water. The pH adjuster is used to adjust the pH value of the CMP slurry to 9.5 to 10.5. Through the combination of the above components, the polishing slurry, under alkaline conditions, possesses a comprehensive effect of surface oxidation, complexation and desorption, selective protection, and mechanical removal, thereby meeting the process requirements for polishing rhodium interconnect layers.

[0008] A further preferred embodiment of the surface-functionalized nanodiamond abrasive includes a single-crystal nanodiamond core, a rhodium-containing catalytic center layer disposed on the surface of the single-crystal nanodiamond core, and an organic polymer buffer dispersion layer disposed on the outside of the rhodium-containing catalytic center layer. The single-crystal nanodiamond core provides stable micro-cutting and mechanical removal capabilities. The rhodium-containing catalytic core layer enhances the interfacial reactivity between the abrasive and the polished rhodium surface, promoting the oxidation reaction on the rhodium surface. The organic polymer buffer dispersion layer reduces interparticle agglomeration, improves slurry dispersion stability, and acts as a flexible buffer at the polishing interface to reduce scratches and defects caused by direct impact from hard abrasives.

[0009] Further preferably, the average particle size of the single-crystal nanodiamond core is 10 nm to 30 nm. By controlling the abrasive particle size within this range, sufficient mechanical removal capability of the abrasive can be ensured, while also improving the dispersion stability of the slurry and reducing the risk of surface scratches caused by large particles. Preferably, the rhodium in the rhodium-containing catalytic core layer is trivalent rhodium; the organic polymer buffer dispersion layer is formed of polyethylene glycol or its derivatives. Trivalent rhodium is beneficial for forming stable catalytic active sites on the abrasive surface, while the outer polymer layer formed by polyethylene glycol or its derivatives is beneficial for improving aqueous phase dispersibility, interfacial wettability, and buffer protection during the polishing process.

[0010] More preferably, the oxidant is potassium persulfate, the complexing agent is ethylenediamine-N,N'-disuccinic acid or its alkali metal salt, and the selectivity control agent is polyaspartic acid or its alkali metal salt. Among them, potassium persulfate is used to provide oxidation capacity at the polishing interface to promote the formation of a reaction layer on the rhodium surface that can be mechanically removed and complexed away; ethylenediamine-N,N'-disuccinic acid or its alkali metal salt is used to complex the products on the oxidized rhodium surface to prevent the reaction products from redepositing on the surface; polyaspartic acid or its alkali metal salt is preferentially adsorbed on the surface of the dielectric layer, thereby inhibiting the removal of non-target layers and selectively protecting them, and improving the selectivity of the rhodium layer relative to the dielectric layer during the polishing process.

[0011] More preferably, the chemical mechanical polishing fluid also includes one or more of surfactants, corrosion inhibitors, and defoamers; Surfactants are used to improve slurry wettability and particle dispersion, corrosion inhibitors are used to suppress excessive corrosion or uneven reactions at non-target interfaces, and defoamers are used to reduce the impact of foam generated during slurry circulation and high-speed polishing on the stability of the slurry supply and the uniformity of polishing. By adding these auxiliary components, the stability and applicability of the polishing slurry in actual process environments can be further improved.

[0012] A second aspect of the present invention provides a method for preparing surface-functionalized nanodiamond abrasives, comprising the following steps: S1 provides carboxylated monodisperse nanodiamond precursors; S2. The carboxylated monodisperse nanodiamond precursor is reacted with a rhodium-containing organometallic complex in a solvent, so that the rhodium-containing component is chemically bonded to the surface of the nanodiamond to form a rhodium-containing catalytic central layer, thus obtaining a rhodium-functionalized nanodiamond intermediate. S3. The rhodium-functionalized nanodiamond intermediate is reacted with the end-functionalized water-soluble polymer to graft the water-soluble polymer onto the surface of the rhodium-functionalized nanodiamond intermediate, forming an organic polymer buffer dispersion layer, thus obtaining surface-functionalized nanodiamond abrasive.

[0013] In the above preparation method, the carboxylated monodisperse nanodiamond precursor obtained in step S1 is used to provide a high specific surface area, surface active sites, and uniform particle base; in step S2, by introducing a rhodium-containing organometallic complex, a stable rhodium-containing catalytic center layer is formed on the nanodiamond surface, so that the resulting abrasive not only has mechanical removal ability, but also has a catalytic effect to promote the oxidation reaction of the rhodium surface interface; in step S3, by grafting a water-soluble polymer on the outer layer, a coating layer with flexible buffering and dispersion stabilizing effect is further formed on the outer side of the particles, thereby obtaining a surface-functionalized nanodiamond abrasive suitable for the rhodium interconnect layer CMP process.

[0014] More preferably, step S1 includes: subjecting the detonation-method nanodiamond powder to mixed acid oxidation purification, followed by field flow fractionation or gel chromatography fractionation to obtain a carboxylated monodisperse nanodiamond precursor. Mixed acid oxidation purification can remove non-diamond phases and impurities from the nanodiamonds and introduce reactive groups such as carboxyl groups onto the particle surface; Field flow fractionation or gel chromatography fractionation can make the particle size distribution more concentrated and improve the monodispersity of the precursor, thus providing a basis for the uniform construction of the subsequent rhodium-containing catalytic center layer and organic polymer buffer dispersion layer.

[0015] More preferably, in step S2, the rhodium-containing organometallic complex is rhodium acetylacetonate, and the reaction is carried out at 60°C to 80°C for 4 to 10 hours under an inert atmosphere; in step S3, the end-functionalized water-soluble polymer is mercapto-terminated polyethylene glycol monomethyl ether, and the reaction is carried out at 50°C to 70°C for 10 to 14 hours in the presence of a free radical initiator.

[0016] By controlling the above conditions, it is beneficial for the stable bonding of rhodium-containing components on the surface of nanodiamonds, and for polyethylene glycol segments to form a more uniform grafted coating structure on the outer layer, thereby taking into account catalytic activity, interfacial stability and dispersion buffering effect.

[0017] A third aspect of the present invention provides a method for preparing the above-described chemical mechanical polishing slurry for rhodium interconnect layers, comprising the following steps: P1. Add the complexing agent and the selectivity control agent to a portion of deionized water and stir to dissolve. P2. Add surface-functionalized nanodiamond abrasive to the mixture obtained in step P1, and perform mechanical stirring and / or ultrasonic dispersion. P3. Add pH adjuster to adjust the pH of the mixture to 9.5-10.5; P4. Add deionized water to the target total volume, mix well, and obtain the main polishing solution; P5. Add an oxidant to the main liquid of the forward polishing slurry and mix well to obtain the working solution of the chemical mechanical polishing slurry.

[0018] In the above preparation method, the complexing agent and the selectivity control agent are dissolved first, which is conducive to forming a uniform and stable base liquid environment; then the surface-functionalized nanodiamond abrasive is added and dispersed, which can make the abrasive uniformly distributed in the liquid phase; then the pH adjuster is used to adjust the system to an alkaline range suitable for rhodium surface oxidation and complexation; finally, the oxidant is added before use, which can reduce the impact of the oxidant on the stability of other components during long-term storage. The above step-by-step preparation method not only improves the storage stability of the polishing fluid, but also ensures good interfacial reactivity and process consistency during use.

[0019] Preferably, the oxidant is stored separately from the main polishing solution and is added to the main polishing solution immediately before polishing in the form of solid powder or high-concentration solution. This two-component storage and mixing before use can avoid side reactions or activity decay of the oxidant with complexing agents, polymer coatings or other active components during long-term storage, thereby helping to maintain the long-term stability and batch consistency of the polishing solution.

[0020] A fourth aspect of the present invention provides the application of the above-described chemical mechanical polishing slurry in the chemical mechanical polishing of semiconductor wafers containing rhodium or rhodium-based alloy interconnect layers; Chemical mechanical polishing (CMP) slurries are used to remove overfilled rhodium or rhodium-based alloy materials from wafer surfaces and to achieve planarization of interconnect layer surfaces. Through the synergistic effect of interfacial catalysis by surface-functionalized nanodiamond abrasives, surface oxidation by oxidants, complexation by reaction products of complexing agents, and protection of non-target layers by selective control agents, CMP slurries can reduce surface defects and damage to non-target layers while ensuring high removal efficiency of rhodium interconnect layers. They are suitable for CMP processes in advanced integrated circuit interconnect structures.

[0021] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: I. This invention employs surface-functionalized monodisperse nanodiamond abrasives with a structure of "single-crystal nanodiamond core—rhodium-containing catalytic center layer—organic polymer buffer dispersion layer." The single-crystal nanodiamond core provides strong mechanical cutting capability, the rhodium-containing catalytic center layer enhances the catalytic oxidation capability of the polishing interface, and the organic polymer buffer dispersion layer improves the dispersion stability of particles in the polishing fluid and reduces mechanical impact caused by hard contact. Through this structural design, combined with potassium persulfate oxidant and ethylenediamine-N,N'-disuccinic acid complexing agents, a reaction layer can be formed on the rhodium surface and promptly removed, thus achieving both a high removal rate and low surface roughness.

[0022] Second, this invention adds polyaspartic acid or its alkali metal salt to the polishing solution as a selective control agent, which enables it to preferentially adsorb and protect the surface of non-target layers, thereby reducing the risk of excessive removal of the dielectric layer and related barrier / lining layers; at the same time, the overall pH of the polishing solution is controlled within the alkaline range of 9.5 to 10.5, and the main solution and oxidant are stored separately and mixed before use, which is beneficial to balance the long-term stability of the polishing solution and the interfacial reactivity during use.

[0023] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0025] Figure 1 This is a flowchart of the preparation method of the polishing fluid of the present invention. Detailed Implementation

[0026] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0027] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0028] like Figure 1 As shown, this embodiment of the invention provides a chemical mechanical polishing slurry for rhodium interconnect layers, its preparation method, and its application. The polishing slurry uses surface-functionalized nanodiamond abrasive as the main component for the synergistic effect of mechanical removal and interfacial catalysis. Through the combination of oxidants, complexing agents, selectivity control agents, and alkaline systems, it achieves efficient removal of rhodium interconnect layer materials, formation of low-defect surfaces, and highly selective protection of the dielectric layer.

[0029] In this invention, the chemical mechanical polishing slurry comprises, by weight percentage, 0.05wt% to 0.30wt% of surface-functionalized nanodiamond abrasive, 0.50wt% to 3.00wt% of oxidant, 0.20wt% to 1.50wt% of complexing agent, 0.001wt% to 0.010wt% of selectivity control agent, pH adjuster, and the balance being deionized water; pH adjusters are used to adjust and maintain the pH value of the polishing solution between 9.5 and 10.5. The preferred oxidant is potassium persulfate, the preferred complexing agent is ethylenediamine-N,N'-disuccinic acid or its alkali metal salt, and the preferred selectivity control agent is polyaspartic acid or its alkali metal salt. If necessary, one or more of surfactants, corrosion inhibitors, and defoamers may be added to further improve the system's wettability, storage stability, and process adaptability.

[0030] Example 1: Preparation of surface-functionalized nanodiamond abrasive This embodiment illustrates the preparation process of the defined surface-functionalized nanodiamond abrasive.

[0031] S1. Preparation of carboxylated monodisperse nanodiamond precursors; Using detonation-processed nanodiamond powder as the initial raw material, a three-necked flask was added. A mixed acid solution of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 3:1 was added, maintaining a liquid-to-solid ratio of 50:1. The mixture was heated to 220℃±5℃ in an oil bath and continuously refluxed for 36–48 hours to fully remove amorphous carbon, graphite phase, and other impurities from the raw material, while simultaneously introducing oxygen-containing functional groups such as carboxyl and hydroxyl groups onto the surface of the nanodiamond. After the reaction, the mixture was cooled to room temperature and then slowly diluted in a large amount of ice water. The solid was then separated by centrifugation at 15,000 rpm for 30 minutes and repeatedly washed with deionized water until the washing solution was nearly neutral. The washed solids were redispersed in deionized water and treated with an ultrasonic cell disruptor with a power of at least 500W for about 1 hour to obtain a well-dispersed precursor suspension. Subsequently, field flow fractionation or gel permeation chromatography was used for particle size fractionation, collecting narrow particle size fractions with a hydrodynamic diameter of approximately 15 nm ± 3 nm. These fractions were then concentrated under reduced pressure at temperatures below 50°C to obtain carboxylated monodisperse nanodiamond hydrosols with a solid content of 5 wt%–10 wt%.

[0032] S2, Introducing a rhodium-containing catalytic central layer; Take 10 g of the above carboxylated monodisperse nanodiamond hydrosol, based on the mass of solid nanodiamonds, and transfer it to a reaction flask equipped with a reflux condenser. Add 200 mL of anhydrous ethanol as the reaction solvent. Under nitrogen protection, add 0.3 g of rhodium acetylacetone, making its mass ratio to nanodiamonds approximately 3 wt%. Heat the mixture to 70 °C ± 2 °C and reflux for 8 hours with magnetic stirring. In this process, the rhodium center in rhodium acetylacetonate undergoes surface coordination and ligand exchange reactions with the carboxyl groups on the surface of nanodiamond, thereby forming a stable rhodium-containing catalytic center layer on the surface of nanodiamond. After the reaction is completed, the mixture is cooled to room temperature and centrifuged to obtain a solid product. The product is then washed three times with anhydrous ethanol and acetone to remove unreacted rhodium acetylacetonate and byproducts. Subsequently, the product is dried in a vacuum drying oven at 40°C for 6 hours to obtain a rhodium-functionalized nanodiamond intermediate.

[0033] S3. Construct an organic polymer buffer dispersion layer on the outside of the intermediate; Rh-ND can be dispersed in anhydrous tetrahydrofuran and its surface can be thiolized to further improve grafting efficiency. Specifically, Rh-ND is dispersed in a toluene solution containing a small amount of 3-mercaptopropyltrimethoxysilane and stirred at room temperature for about 12 hours to introduce thiol groups onto its surface. Subsequently, thiol-terminated polyethylene glycol monomethyl ether is added to the dispersion system. The mass of the added polymer can be about 20 wt% of the mass of the nanodiamonds, and the number average molecular weight of the polyethylene glycol monomethyl ether is preferably about 2000 Da. Then, under a nitrogen atmosphere, a free radical initiator, such as azobisisobutyronitrile, is added to the system and the reaction is carried out at 60℃±2℃ for 12 hours. This reaction enables the reactive groups at the polymer ends to form a stable bond with the surface of the intermediate, thereby constructing an organic polymer buffer dispersion layer on the outer layer. After the reaction is completed, the solid is collected by centrifugation and washed three times alternately with tetrahydrofuran and ethanol to remove unbound free polymer. The resulting product is redispersed in deionized water and filtered through a 0.1 μm filter membrane to obtain an aqueous dispersion of surface-functionalized nanodiamond abrasive.

[0034] The functionalized abrasive obtained in this embodiment was tested by dynamic light scattering and its average particle size was about 17.8 nm, and its polydispersity index (PDI) was 0.076. After the 1 wt% aqueous dispersion was left to stand for 30 days, no visible precipitate was observed and the particle size did not change significantly, indicating that the abrasive has good monodispersity and long-term storage stability.

[0035] Example 2: Preparation of the main and working solutions of a chemical mechanical polishing slurry This embodiment is used to illustrate the composition and preparation process of the defined polishing fluid.

[0036] P1. Add approximately 80% of the total formula amount of deionized water to a clean mixing tank, control the liquid temperature at 20℃~25℃, and start stirring at 100rpm~200rpm. Then add 0.80wt% of the complexing agent ethylenediamine-N,N'-disuccinate trisodium and 0.005wt% of the selectivity control agent sodium polyaspartate, and continue stirring until completely dissolved. P2. Slowly add the surface-functionalized nanodiamond abrasive prepared in Example 1 to the mixture, so that the amount added is 0.15 wt% on a solids basis, and increase the stirring speed to 500 rpm. At the same time, turn on the ultrasonic dispersion device for about 30 minutes to ensure that the abrasive is uniformly dispersed and does not agglomerate significantly. Then add the surfactant Triton X-100 0.01 wt%, the corrosion inhibitor benzotriazole 0.005 wt%, and if necessary, add the defoamer about 0.001 wt%. Continue stirring for about 10 minutes. P3. Adjust the pH value to 10.0±0.1 using a borax-potassium hydroxide buffer system; P4. Add deionized water to the target total volume and filter through a 0.2μm polyethersulfone filter to obtain a uniform and stable polishing solution.

[0037] P5. Before use, add the oxidant separately to the main solution to obtain the working solution. Potassium persulfate is preferred as the oxidant, and it can be added at 1.50 wt% of the total mass of the final working solution. It can be added as a solid powder or a high-concentration aqueous solution. After addition, circulate and stir for 5 to 10 minutes to ensure thorough mixing, thus obtaining a working solution that can be directly used for chemical mechanical polishing.

[0038] Example 3: Basic performance testing of polishing slurry on rhodium film wafers This embodiment is used to illustrate the application and verify the removal efficiency and surface quality of the rhodium layer by the polishing slurry of the present invention.

[0039] A 300mm diameter monitoring wafer was used as the test sample, and a 100nm thick PVD rhodium film was prepared on its surface. A 300mm wafer CMP machine was used for polishing, and a porous polyurethane polishing pad was used. The working fluid prepared in Example 2 was introduced into the device. The polishing head pressure was set to 2.5 psi, the polishing head speed was set to 87 rpm, the polishing disc speed was set to 93 rpm, the polishing fluid flow rate was set to 200 mL / min, and the polishing time was set to 30 seconds.

[0040] Test results show that after polishing with the polishing solution of this invention, the rhodium removal rate can reach 445 nm / min. Atomic force microscopy scanning of the polished surface within a 5 μm × 5 μm range revealed a surface roughness Ra of approximately 0.13 nm, indicating that high smoothness and extremely low surface roughness can be achieved. Further, the removal rate of thermally grown SiO2 wafers was tested under the same process conditions, and the result was 1.7 nm / min. Based on this, the selectivity ratio of SiO2 can be calculated to be approximately 262:1. The above results demonstrate that the polishing slurry of the present invention can not only achieve a high rhodium removal rate, but also has significantly higher selectivity for the dielectric layer.

[0041] Example 4: Patterned Wafer Integration Verification This embodiment further verifies the applicability of the polishing slurry of the present invention in advanced interconnect structures.

[0042] First, a patterned test wafer is prepared, using a 300mm blank silicon wafer as a substrate, and a 500nm thick PECVD SiO2 layer is deposited. Subsequently, a trench array with a linewidth of 30nm and a spacing of 30nm was formed using photolithography and dry etching processes; Subsequently, a 2 nm thick ALD TaN barrier layer and a 3 nm thick PVD Ru liner layer were deposited sequentially, and an 80 nm thick Rh layer was filled by electrochemical deposition to form an overfilled structure of about 20%.

[0043] During the CMP process, the polishing slurry prepared in Example 2 was used as the main solution, and 1.5 wt% potassium persulfate was added before use to form the working solution. The polishing endpoint was controlled by optical endpoint detection, and after reaching the endpoint, over-polishing was continued for 5%. After polishing, conventional brushing and megasonic cleaning processes were used, along with diluted ammonia or semiconductor-specific cleaning solution to remove residual particles and slurry from the surface.

[0044] The patterned wafers after polishing were inspected, and the results showed that: The top of the Rh line in the trench is relatively flat, and the average value of the dish-shaped depression is about 1.2nm, so the erosion is negligible; the deviation between the measured line resistance value and the theoretical model is controlled within ±5%, indicating that the linewidth loss is well controlled. According to Surfscan analysis, the density of defects larger than 90nm is approximately 0.08 defects / cm2. Electromigration tests were conducted at 225℃ and a current density of 2MA / cm2, and the median failure time was approximately 70 times longer than that of copper interconnects of the same size. The above results show that the polishing fluid of the present invention is not only suitable for polishing blank film layers, but also meets the requirements of advanced node patterned rhodium interconnect structures for low dish depression, low erosion, low defects and high reliability.

[0045] Comparative Example 1: Polishing slurry system using traditional SiO2 abrasives The surface-functionalized nanodiamond abrasive in Example 2 was replaced with the same amount of commercially available high-purity colloidal SiO2 abrasive with a particle size of approximately 35 nm, while the remaining components and preparation methods remained unchanged.

[0046] Polishing tests were performed using the same equipment and process parameters as in Example 3. The results showed that the rhodium removal rate was only 22 nm / min, which was much lower than that of the system of the present invention; After polishing, obvious hazy defects and scratches appeared on the surface, and the surface roughness Ra of AFM test was greater than 2nm. The selectivity ratio of the SiO2 dielectric layer was less than 2:1, which could not meet the requirements of patterned interconnect polishing. This comparative example shows that traditional SiO2 abrasives are difficult to achieve both sufficient removal rate and low damage surface quality in rhodium CMP, and it is also difficult to obtain high selectivity.

[0047] Comparative Example 2: Nanodiamond abrasive system without rhodium catalytic center Nanodiamond abrasive, namely PEG-ND, was prepared by grafting polyethylene glycol without introducing a rhodium-containing catalytic center, and polishing slurry was prepared according to the formulation and method of Example 2, while keeping other components and process conditions unchanged.

[0048] The test was conducted under the same polishing conditions as in Example 3; The results showed that the rhodium removal rate decreased to approximately 150 nm / min. Although this is still an improvement over the traditional SiO2 abrasive system, the removal rate is significantly lower compared to the functionalized nanodiamond abrasive with a rhodium-containing catalytic core layer of this invention. This indicates that the rhodium-containing catalytic core layer on the abrasive surface can significantly enhance the oxidation reaction and removal efficiency at the polishing interface, which is an important technical feature for achieving high rhodium removal rates.

[0049] As can be seen from the above embodiments and comparative examples, the present invention, by sequentially constructing a rhodium-containing catalytic center layer and an organic polymer buffer dispersion layer on the surface of nanodiamond, enables the abrasive to possess hard mechanical cutting capabilities, interfacial catalytic oxidation promoting capabilities, and dispersion buffering capabilities. Furthermore, by combining potassium persulfate oxidant, ethylenediamine-N,N'-disuccinic acid complexing agent, polyaspartic acid selectivity control agent, and alkaline buffer system, high removal rate, low surface roughness, and high dielectric layer selectivity can be achieved during the CMP process of the rhodium interconnect layer.

[0050] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A chemical mechanical polishing slurry for rhodium interconnect layers, characterized in that, By weight percentage, it includes the following components: Surface-functionalized nanodiamond abrasives, 0.05wt%~0.30wt%; Oxidizing agent 0.50wt%~3.00wt%; Complexing agent 0.20wt%~1.50wt%; Selective control agent: 0.001 wt% to 0.010 wt%; pH adjuster, wherein the pH adjuster is used to adjust the pH value of the chemical mechanical polishing slurry to 9.5-10.5; The remainder is deionized water; The surface-functionalized nanodiamond abrasive includes a single-crystal nanodiamond core, a rhodium-containing catalytic center layer disposed on the surface of the single-crystal nanodiamond core, and an organic polymer buffer dispersion layer disposed on the outside of the rhodium-containing catalytic center layer.

2. The chemical mechanical polishing slurry for rhodium interconnect layers according to claim 1, characterized in that: The average particle size of the single-crystal nanodiamond core is 10nm to 30nm; the rhodium in the rhodium-containing catalytic center layer is trivalent rhodium; and the organic polymer buffer dispersion layer is formed of polyethylene glycol or its derivatives.

3. The chemical mechanical polishing slurry for rhodium interconnect layers according to claim 1 or 2, characterized in that: The oxidant is potassium persulfate; the complexing agent is ethylenediamine-N,N'-disuccinic acid or its alkali metal salt. The selectivity control agent is polyaspartic acid or its alkali metal salt.

4. The chemical mechanical polishing slurry for rhodium interconnect layers according to any one of claims 1 to 3, characterized in that: It also includes one or more of surfactants, corrosion inhibitors, and defoamers.

5. A method for preparing surface-functionalized nanodiamond abrasive, characterized in that, Includes the following steps: S1 provides carboxylated monodisperse nanodiamond precursors; S2. The carboxylated monodisperse nanodiamond precursor is reacted with a rhodium-containing organometallic complex in a solvent, so that the rhodium-containing component is chemically bonded to the surface of the nanodiamond to form a rhodium-containing catalytic central layer, thereby obtaining a rhodium-functionalized nanodiamond intermediate. S3. The rhodium-functionalized nanodiamond intermediate is reacted with an end-functionalized water-soluble polymer to graft the water-soluble polymer onto the surface of the rhodium-functionalized nanodiamond intermediate, forming an organic polymer buffer dispersion layer, thereby obtaining surface-functionalized nanodiamond abrasive.

6. The method for preparing surface-functionalized nanodiamond abrasive according to claim 5, characterized in that: Step S1 includes: purifying the detonation-method nanodiamond powder by mixed acid oxidation, and then fractionating it by field flow fractionation or gel chromatography to obtain a carboxylated monodisperse nanodiamond precursor.

7. The method for preparing surface-functionalized nanodiamond abrasives according to claim 5 or 6, characterized in that: In step S2, the rhodium-containing organometallic complex is rhodium acetylacetone, and the reaction is carried out at 60°C to 80°C for 4 to 10 hours under an inert atmosphere. In step S3, the end-functionalized water-soluble polymer is a mercapto-terminated polyethylene glycol monomethyl ether, and the reaction is carried out at 50°C to 70°C for 10 to 14 hours in the presence of a free radical initiator.

8. A method for preparing the chemical mechanical polishing slurry for rhodium interconnect layers according to any one of claims 1 to 4, characterized in that, Includes the following steps: P1. Add the complexing agent and the selectivity control agent to a portion of deionized water and stir to dissolve. P2. Add surface-functionalized nanodiamond abrasive to the mixture obtained in step P1, and perform mechanical stirring and / or ultrasonic dispersion. P3. Add pH adjuster to adjust the pH of the mixture to 9.5-10.5; P4. Add deionized water to the target total volume, mix well, and obtain the main polishing solution; P5. Before use, add an oxidant to the main polishing solution and mix evenly to obtain the working solution of the chemical mechanical polishing slurry.

9. The method for preparing a chemical mechanical polishing slurry according to claim 8, characterized in that: The oxidant is stored separately from the main polishing solution and is added to the main polishing solution immediately before polishing in the form of a solid powder or a high-concentration solution.

10. The use of the chemical mechanical polishing slurry according to any one of claims 1 to 4 in the chemical mechanical polishing of semiconductor wafers containing rhodium or rhodium-based alloy interconnect layers.

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