Electrochemical mechanical polishing compositions and their applications, silicon carbide wafers

Abstract

This invention discloses an electrochemical mechanical polishing (ECMP) composition and its application, as well as silicon carbide wafers, relating to the field of semiconductor technology. The ECMP composition comprises two acidic substances and abrasive grains working synergistically, employing a "cathodic reduction reaction + mechanical" mechanism to achieve a polishing effect with minimal damage to silicon carbide wafers. The acidic substances provide hydrogen ions while suppressing side reactions. During polishing, the layered structure of the abrasive grains undergoes shear slip, and the synergistic effect of the acidic substances enhances interfacial reactivity, significantly reducing the polishing voltage requirement and achieving zero lattice damage. Furthermore, the abrasive grains are recyclable, reducing costs. The ECMP polishing composition operates in an acidic environment, is free of heavy metals, and can be directly discharged after neutralization, resulting in low treatment costs. In addition, the polishing process is simple and controllable, and is expected to further promote the development of silicon carbide semiconductor manufacturing.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to an electrochemical mechanical polishing composition and its application, and silicon carbide wafers. Background Technology

[0002] Electrochemical mechanical polishing (ECMP) is a composite precision polishing technique that combines electrochemical dissolution with mechanical micro-abrasion. It is mainly used for global planarization of wafer surfaces.

[0003] Silicon carbide, as a representative of third-generation wide-bandgap semiconductor materials, has broad application prospects in high-temperature, high-frequency, and high-power power electronic devices due to its excellent properties such as high breakdown field strength, high thermal conductivity, and high electron saturation drift velocity. However, silicon carbide's extremely high hardness and chemical inertness also make it a typical difficult-to-process material.

[0004] Traditional mechanical polishing methods rely on the mechanical grinding action of diamond abrasives, which inevitably introduces scratches, microcracks, and lattice damage layers into the subsurface. These defects significantly degrade the reliability and lifespan of devices. Chemical mechanical polishing (CMP) technology improves surface quality to some extent, but its material removal rate is low, and it is still difficult to completely avoid subsurface damage for hard and brittle silicon carbide. It also suffers from problems such as abrasive residue and polishing slurry contamination.

[0005] Existing ECMP technology still has many significant drawbacks when applied to silicon carbide wafer polishing, such as high polishing slurry cost, low efficiency, and severe lattice damage.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide an electrochemical mechanical polishing composition and its application, as well as silicon carbide wafers, to solve the above-mentioned technical problems.

[0008] This invention is implemented as follows:

[0009] In a first aspect, embodiments of the present invention provide an electrochemical mechanical polishing composition comprising the following components:

[0010] The first acidic substance at concentrations of 0.05 mol / L to 0.45 mol / L, the second acidic substance at concentrations of 0.01 mol / L to 0.25 mol / L, H₂O₂ at concentrations of 0.08 mol / L to 0.12 mol / L, and 0.2 kg / m 3 -1kg / m 3 abrasive grains;

[0011] The first acidic substance is selected from at least one of phosphoric acid, sulfuric acid, aminosulfonic acid, EDTA and oxalic acid;

[0012] The second acidic substance is selected from at least one of ascorbic acid, isoascorbic acid, citric acid, tartaric acid, hydroxylamine hydrochloride, and malic acid;

[0013] The abrasive particles are boron nitride with a layered structure.

[0014] In an optional embodiment, the first acidic substance is 0.08 mol / L-0.12 mol / L phosphoric acid or 0.3 mol / L-0.4 mol / L oxalic acid;

[0015] And / or, the second acidic substance is 0.018 mol / L to 0.026 mol / L of ascorbic acid or 0.1 mol / L to 0.2 mol / L of hydroxylamine hydrochloride.

[0016] In an optional embodiment, the mass concentration of boron nitride is 0.4 kg / m³. 3 -0.6kg / m 3 .

[0017] In an optional embodiment, the boron nitride particle size is 10 nm to 100 nm.

[0018] Secondly, embodiments of the present invention provide an application of the aforementioned electrochemical mechanical polishing composition in the polishing of silicon carbide wafers.

[0019] Thirdly, embodiments of the present invention provide a method for polishing a silicon carbide wafer, comprising the following steps:

[0020] Abrasive pretreatment, preparation of polishing slurry, polishing treatment, and post-treatment; wherein the polishing slurry includes the aforementioned electrochemical mechanical polishing composition;

[0021] The abrasive pretreatment includes: heating boron nitride at 280℃-320℃ for 0.8h-1.5h, followed by immersion in TiCl4-ethanol solution for 25min-60min;

[0022] The preparation of the polishing slurry includes: mixing the first acidic substance, the second acidic substance and the abrasive particles in a certain proportion to obtain a polishing slurry with a Zeta potential > 40mV.

[0023] In an optional embodiment, the heat treatment in the abrasive pretreatment is carried out in an N2 / H2O environment with a volume ratio of (3-8):1.

[0024] In an optional embodiment, the polishing process uses a flow rate of 180 mL / min–220 mL / min and a pressure of 0.3 N / cm. 2-0.8N / cm 2 The rotation speed was 35 rpm to 60 rpm, and the temperature was 35℃ to 45℃. The removal rate of the softening layer material on the silicon carbide wafer surface was 380 nm / min to 450 nm / min.

[0025] In an optional implementation, post-processing includes abrasive grain recovery and uniform processing of silicon carbide wafers;

[0026] Among them, abrasive recycling includes collecting the waste liquid after cleaning the polishing process.

[0027] Fourthly, embodiments of the present invention provide a silicon carbide wafer, which is prepared using the aforementioned method;

[0028] The surface roughness of the silicon carbide wafer is 0.02nm-0.12nm, and the subsurface damage is 0; the material selection ratio of SiC:SiO2 is 15:1-20:1.

[0029] The present invention has the following beneficial effects:

[0030] The electrochemical mechanical polishing composition provided in this embodiment of the invention achieves minimal damage to silicon carbide wafers during polishing by employing a "cathodic reduction reaction + mechanical" mechanism; the analysis is as follows:

[0031] The reduction reaction is directly supplied with electrons from the cathode, independent of the hole concentration in the material, and the reaction product is an easily removable silicon layer. The two acidic substances provide hydrogen ions while suppressing side reactions. The Si-H bonds generated in the byproducts form a hydrogen terminal layer on the silicon carbide wafer surface, which helps reduce surface energy and inhibits oxide layer regeneration after polishing. During polishing, the layered structure of the abrasive grains undergoes shear slip, which, in conjunction with the acidic substances, enhances interfacial reactivity, significantly reducing the polishing voltage requirement and minimizing lattice damage. This achieves precise control of the dynamic balance between electrochemical anodizing and mechanical removal. Furthermore, the abrasive grains are recyclable, reducing costs. The ECMP polishing composition is an acidic environment system, free of heavy metals, and can be directly discharged after neutralization, resulting in low treatment costs. In addition, the polishing process is simple and controllable, which is expected to further promote the development of silicon carbide semiconductor manufacturing. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] In a first aspect, embodiments of the present invention provide an electrochemical mechanical polishing composition comprising the following components:

[0034] The first acidic substance at concentrations of 0.05 mol / L to 0.45 mol / L, the second acidic substance at concentrations of 0.01 mol / L to 0.25 mol / L, H₂O₂ at concentrations of 0.08 mol / L to 0.12 mol / L, and 0.2 kg / m 3 -1kg / m 3 abrasive grains;

[0035] The first acidic substance is selected from at least one of phosphoric acid, sulfuric acid, aminosulfonic acid, EDTA and oxalic acid;

[0036] The second acidic substance is selected from at least one of ascorbic acid, isoascorbic acid, citric acid, tartaric acid, hydroxylamine hydrochloride, and malic acid;

[0037] The abrasive particles are boron nitride with a layered structure.

[0038] It should be noted that, during the polishing process, the ECMP polishing composition provided by this invention forms soft silicon on the silicon carbide surface due to acidic substances. The adjustment of the abrasive-coordinated process parameters in the cathode reduction polishing composition achieves a removal effect with minimal lattice damage. A detailed analysis follows:

[0039] Traditional ECMP polishing compositions operate in an alkaline environment. Their polishing mechanism involves anodic oxidation (e.g., SiC → SiO2) requiring hole injection, which can easily lead to lattice damage. N-type SiC has few holes, while P-type is prone to over-etching. The ECMP polishing composition provided by this invention operates in an acidic environment. Its polishing mechanism utilizes a cathodic reduction reaction: SiC + 4H₂O + +4e - →Si+CH4 (electron participation) avoids hole damage; compared with the polishing mechanisms of the two, the electrons in this invention are directly supplied by the cathode, which does not depend on the hole concentration of the material, and the reaction product is an easily removable silicon layer (non-hard SiO2).

[0040] The provision of two acidic substances serves two purposes. The first acid primarily provides a high concentration of hydrogen ions, accelerating the reduction reaction. The second acid primarily suppresses the reduction side reaction of hydrogen ions (2H+). + +2e - →H2); the two synergistic effects together enhance the reaction kinetics of ECMP during silicon carbide polishing.

[0041] Oxidant H2O2 can regulate interfacial reaction kinetics, suppress side reactions, and dynamically control oxide layer thickness, which is beneficial for achieving synergistic polishing, suppressing hydrogen evolution side reactions, and improving electron utilization.

[0042] Utilizing the byproducts generated in the reaction (CeSi+4H) + +4e - →SiH4) The Si-H bonds in the silicon carbide wafer form a hydrogen terminal layer, which is beneficial for passivating the dangling bonds on the silicon carbide surface, reducing the surface energy, and inhibiting the regeneration of the oxide layer after polishing.

[0043] The abrasive used is boron nitride (h-BN) with a layered structure. During the polishing process, the layered structure generates shear slip, which enhances the interfacial reactivity, significantly reduces the polishing voltage requirement, and achieves zero lattice damage.

[0044] In an optional embodiment, the first acidic substance is 0.08 mol / L-0.12 mol / L phosphoric acid or 0.3 mol / L-0.4 mol / L oxalic acid;

[0045] And / or, the second acidic substance is 0.018 mol / L to 0.026 mol / L of ascorbic acid or 0.1 mol / L to 0.2 mol / L of hydroxylamine hydrochloride.

[0046] It should be noted that the amounts of phosphoric acid, oxalic acid, ascorbic acid, and hydroxylamine hydrochloride can be adjusted reasonably according to the actual amount of material being processed. In the optimal implementation method, the acidic substances used are phosphoric acid and ascorbic acid used in combination, and oxalic acid and hydroxylamine hydrochloride used in combination.

[0047] In an optional embodiment, the mass concentration of boron nitride is 0.4 kg / m³. 3 -0.6kg / m 3 .

[0048] It should be noted that if the boron nitride concentration is too low, the number of abrasive particles will be insufficient, resulting in a low removal rate; if the boron nitride concentration is too high, the abrasive particles will agglomerate, increasing the risk of scratches.

[0049] In an optional embodiment, the boron nitride particle size is 10 nm to 100 nm.

[0050] It should be noted that, considering the balance between polishing efficiency, surface quality, and cost, the optimal implementation method selects a boron nitride particle size of 20 nm.

[0051] Secondly, embodiments of the present invention provide an application of the aforementioned electrochemical mechanical polishing composition in the polishing of silicon carbide wafers.

[0052] Thirdly, embodiments of the present invention provide a method for polishing a silicon carbide wafer, comprising the following steps:

[0053] Abrasive pretreatment, preparation of polishing slurry, polishing treatment, and post-treatment; wherein the polishing slurry includes the aforementioned electrochemical mechanical polishing composition;

[0054] The abrasive pretreatment includes: heating boron nitride at 280℃-320℃ for 0.8h-1.5h, followed by immersion in TiCl4-ethanol solution for 25min-60min;

[0055] The preparation of the polishing slurry includes: uniformly mixing a first acidic substance, a second acidic substance, and abrasive particles in a specific ratio to obtain a polishing slurry with a Zeta potential > 40 mV. This ensures the polishing slurry is a stable suspension system.

[0056] It should be noted that the purpose of the boron nitride heat treatment is to break the BN bond by high-temperature water vapor, thereby hydroxylating its surface and introducing -OH groups at the edges and defect sites of h-BN to form B-OH and NH groups, which enhances dispersibility and reactivity.

[0057] The concentration of the TiCl4-ethanol solution was 0.001 M. The purpose of immersion treatment in this solution was to anchor Ti on the surface of hydroxylated h-BN. 3+ Ions enhance the chemisorption of the SiC softening layer.

[0058] In an optional embodiment, the heat treatment in the abrasive pretreatment is carried out in an N2 / H2O environment with a volume ratio of (3-8):1.

[0059] It should be noted that the heat treatment is carried out in an N2 / H2O environment, the purpose of which is to precisely control the density of -OH groups on the h-BN surface and avoid damage to the layered structure caused by excessive oxidation.

[0060] In traditional alkaline chemical mechanical polishing, the material selectivity ratio SiC:SiO2 is 1:1-1:10; in the embodiments of the present invention, in acidic reducing electrochemical mechanical polishing, the material selectivity ratio SiC:SiO2 is 15:1-20:1. The improvement in the material selectivity ratio has the following characteristics:

[0061] (1) Precise material removal: While efficiently polishing SiC, the SiO2 dielectric layer is almost undamaged (loss rate is only 5%).

[0062] (2) Ensure device reliability: avoid defects such as gate oxide layer perforation and uneven thickness, and improve breakdown voltage stability;

[0063] (3) Significant cost reduction and efficiency improvement: The required SiO2 deposition thickness is reduced by 20 times, resulting in annual cost savings of up to millions of US dollars;

[0064] (4) The SiC:SiO2 parameter is the core advantage of acid reduction electrochemical mechanical polishing replacing traditional processes, directly driving SiC devices into high-end applications such as electric vehicles and 5G base stations. This parameter also has a profound impact on device performance, process control and cost-effectiveness.

[0065] In an optional embodiment, the polishing process uses a flow rate of 180 mL / min–220 mL / min and a pressure of 0.3 N / cm. 2 -0.8N / cm 2 The rotation speed was 35 rpm to 60 rpm, and the temperature was 35℃ to 45℃. The removal rate of the softening layer material on the silicon carbide wafer surface was 380 nm / min to 450 nm / min.

[0066] It should be noted that when the flow rate decreases, the abrasive particles are not renewed sufficiently, leading to localized overheating; when the flow rate increases, turbulent scouring reduces the residence time of the abrasive particles; in the optimal implementation, the flow rate for polishing is 200 mL / min.

[0067] In an optional embodiment, the cathode potential for polishing is -2.5 ± 0.05 V vs. Ag / AgCl. In other embodiments of the present invention, it can be reasonably adjusted according to actual needs.

[0068] In an optional implementation, post-processing includes abrasive grain recovery and uniform processing of silicon carbide wafers;

[0069] Among them, abrasive recycling includes collecting the waste liquid after cleaning the polishing process.

[0070] Fourthly, embodiments of the present invention provide a silicon carbide wafer, which is prepared using the aforementioned method;

[0071] The surface roughness of the silicon carbide wafer is 0.02nm-0.12nm, and the subsurface damage is 0; the material selection ratio of SiC:SiO2 is 15:1-20:1.

[0072] It should be noted that after the waste liquid is washed, its sediment is collected and subjected to ultrasonic regeneration treatment to prevent the deagglomerated particles from settling and agglomerating again, maintain uniform suspension, and ensure that the abrasive particles are restored to their original single particles.

[0073] The entire polishing process was carried out in a glove box with an N2 atmosphere, where O2 < 0.1 ppm and H2O < 1 ppm.

[0074] In summary, the method for polishing silicon carbide wafers provided in this embodiment of the invention includes the following steps:

[0075] (1) Abrasive pretreatment

[0076] Take abrasive grains h-BN (denoted as BNK-20) and heat them in an environment with a volume ratio of (3-8):1 N2 / H2O and a temperature of 280℃-320℃ for 0.8h-1.5h.

[0077] The heat-treated abrasive particles were immersed in a 0.001 mol / L TiCl4-ethanol solution for 25-60 minutes, followed by centrifugation and cleaning with ultrasonication during the process to obtain modified h-BN.

[0078] (2) Preparation of polishing slurry

[0079] Weigh and mix the first acidic substance (0.08 mol / L-0.12 mol / L phosphoric acid), the second acidic substance (0.018 mol / L-0.026 mol / L ascorbic acid), the oxidizing agent (0.08 mol / L-0.12 mol / L H2O2), and the modified h-BN (0.4 kg / m³) obtained in step (1) in proportion. 3 -0.6kg / m 3 During the process, ultrasonication was used to prepare a polishing solution with a Zeta potential > 40mV.

[0080] (3) Polishing treatment

[0081] The polishing process uses a flow rate of 180 mL / min–220 mL / min and a pressure of 0.3 N / cm. 2 -0.8N / cm 2 The rotation speed is 35rpm-60rpm, the temperature is 35℃-45℃, and the cathode potential is -2.5±0.05 V vs. Ag / AgCl.

[0082] It should be noted that during the polishing process, the volume of the polishing slurry is reasonably prepared according to the actual size (e.g., 8-inch) and quantity of the silicon carbide wafers being processed, with the goal of immersing the silicon carbide wafers in the polishing slurry. The number of silicon carbide wafers being processed is reasonably adjusted according to the actual equipment specifications and production volume.

[0083] (4) Post-processing

[0084] Abrasive recovery: The waste liquid after polishing in step (3) is cleaned. To improve the cleaning efficiency, centrifugation is used. The precipitate after centrifugation is collected, and after ultrasonic regeneration, it is returned to the storage tank to obtain polished silicon carbide wafers.

[0085] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0086] Example 1

[0087] This embodiment provides a method for polishing silicon carbide wafers, including the following steps:

[0088] (1) Abrasive pretreatment

[0089] Abrasive grains h-BN (denoted as BNK-20) with a particle size of 20nm were heated for 1 hour in an environment with N2 / H2O=4:1 and a temperature of 300℃.

[0090] The heat-treated abrasive grains were immersed in a 0.001 mol / L TiCl4-ethanol solution for 30 minutes and then centrifuged and washed, with ultrasonication as an auxiliary process, to obtain modified h-BN.

[0091] (2) Preparation of polishing slurry

[0092] Weigh and mix the first acidic substance (0.1 mol / L phosphoric acid), the second acidic substance (0.02 mol / L ascorbic acid), the oxidant (0.1 mol / L H2O2), and the modified h-BN (0.5 kg / m³) obtained in step (1) in proportion. 3 During the process, ultrasonic treatment was performed (500W, 30min). 100L of polishing solution was prepared, the pH of the polishing solution was measured, and the final pH of the polishing solution was adjusted to 1.5 with HCl solution or Na2CO3 solution to obtain a polishing solution with a Zeta potential >40mV.

[0093] (3) Polishing treatment

[0094] The silicon carbide wafer was polished using the polishing slurry prepared in step (2), wherein the flow rate of the polishing process was 200±10 mL / min and the pressure was 0.5 N / cm. 2 The rotation speed is 50 rpm, the temperature is 40±0.5℃, the cathode potential is -2.5±0.05V vs. Ag / AgCl, the silicon carbide wafer is 8 inches, the number of silicon carbide wafers processed at one time is 25, and the polishing solution can be reused 5 times, that is, the number of silicon carbide wafers that can be processed is 125.

[0095] (4) Post-processing

[0096] Abrasive recovery: The waste liquid after polishing in step (3) is cleaned. To improve the cleaning efficiency, centrifugation (8000 rpm) is used. The precipitate after centrifugation is collected and returned to the storage tank after ultrasonic regeneration at 40 kHz to obtain polished silicon carbide wafers.

[0097] Example 2

[0098] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0099] (2) Preparation of polishing slurry

[0100] The first acidic substance (0.04 mol / L phosphoric acid) and the second acidic substance (0.02 mol / L ascorbic acid).

[0101] Example 3

[0102] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0103] (2) Preparation of polishing slurry

[0104] The first acidic substance (0.1 mol / L phosphoric acid) and the second acidic substance (0.012 mol / L ascorbic acid).

[0105] Example 4

[0106] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0107] (2) Preparation of polishing slurry

[0108] The first acidic substance (0.35 mol / L oxalic acid) and the second acidic substance (0.15 mol / L hydroxylamine hydrochloride).

[0109] Example 5

[0110] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0111] (2) Preparation of polishing slurry

[0112] The first acidic substance (0.1 mol / L phosphoric acid) and the second acidic substance (0.15 mol / L hydroxylamine hydrochloride).

[0113] Example 6

[0114] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0115] (2) Preparation of polishing slurry

[0116] The first acidic substance (0.35 mol / L oxalic acid) and the second acidic substance (0.02 mol / L ascorbic acid).

[0117] Example 7

[0118] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0119] (2) Preparation of polishing slurry

[0120] There is only the first acidic substance (0.1 mol / L phosphoric acid), and no second acidic substance.

[0121] Example 8

[0122] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0123] (2) Preparation of polishing slurry

[0124] It contains only the second acid (0.02 mol / L ascorbic acid), but no first acid.

[0125] Example 9

[0126] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0127] (2) Preparation of polishing slurry

[0128] The polishing solution has a pH of 1.

[0129] Example 10

[0130] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0131] (2) Preparation of polishing slurry

[0132] The polishing solution has a pH of 2.

[0133] Example 11

[0134] This embodiment provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Embodiment 1, the only difference being:

[0135] (1) Abrasive pretreatment

[0136] Boron nitride abrasive particles do not require pretreatment.

[0137] Comparative Example 1

[0138] This comparative example provides a method for polishing silicon carbide wafers, the polishing steps of which are the same as in Example 1, the only difference being:

[0139] (2) The polishing solution is a traditional alkaline polishing solution, which includes the following components: 0.35 mol / L tetramethylammonium hydroxide (TMAH), 4 vol% ammonia (NH4OH), 4 wt% hydrogen peroxide (H2O2), 0.15 mol / L potassium periodate (KIO3), and abrasive particles of 12 kg / m 3Colloidal silica (SiO2).

[0140] Experimental Example 1

[0141] This experimental example is used to study the effect of abrasive particle size on the polishing of silicon carbide wafers. The polishing process is the same as in Example 1, with the only difference being:

[0142] The particle sizes of the abrasive h-BN were 10 nm, 20 nm, 50 nm, and 100 nm. The silicon carbide wafers were uniformly processed before performance measurements were performed. The data for removal rate (the thickness of material removed from the surface of the silicon carbide wafer per unit time) and surface roughness Ra are summarized in Table 1.

[0143] Table 1 Performance parameters for investigating the influence of abrasive particle size

[0144]

[0145] As can be seen from the data in Table 1, the removal rate increases with the increase of abrasive particle size, and the surface roughness of silicon carbide also increases. Considering the balance between efficiency, surface quality and cost, 20nm abrasive particles were selected for further experimental investigation.

[0146] According to statistics, the subsurface damage layer of the 125 silicon carbide wafers processed in Example 1 was 0, and the yield reached 100%.

[0147] Experimental Example 2

[0148] This experimental example is used to study the effect of abrasive type on the polishing of silicon carbide wafers. The polishing process is the same as in Example 1, except that:

[0149] The types and sizes of abrasive particles changed, being 50 nm Al2O3, 30 nm CeO2, and 20 nm h-BN, respectively. Data on removal rate, surface roughness Ra, and subsurface damage layer are summarized in Table 2.

[0150] Table 2 Performance parameters investigating the influence of abrasive type

[0151]

[0152] As can be seen from the data in Table 2, the subsurface damage of h-BN is 0, and the integrity of the silicon carbide wafer is well maintained. This is attributed to the shear slip generated by the layered structure of h-BN during polishing, which, together with the treatment of acidic substances, enhances the interfacial reactivity and significantly reduces the polishing voltage requirement. The silicon layer can be efficiently removed with low pressure during the polishing process, thereby achieving the effect of zero lattice damage.

[0153] Experimental Example 3

[0154] This experimental example is used to study the effect of the polishing flow rate on the polishing of silicon carbide wafers. The polishing process is the same as in Example 1, with the only difference being:

[0155] The polishing flow rates were 100 mL / min, 200 mL / min, and 300 mL / min, respectively. The resulting silicon carbide wafers were uniformly processed and their performance was measured. The data for removal rate, abrasive grain utilization, and uniformity (edge / center Ra ratio) are summarized in Table 3. This test example also summarizes the removal rate, surface roughness Ra (nm), and material selectivity ratio (SiC:SiO2) for Examples 1-11; the relevant data are shown in Table 4.

[0156] Table 3 Performance parameters for investigating the effect of polishing treatment flow rate

[0157]

[0158] As can be seen from the data in Table 3, the uniformity first decreases and then increases with the increase of flow rate; when the flow rate is less than 200 mL / min, the abrasive particles are not renewed enough and local overheating occurs; when the flow rate is greater than 200 mL / min, turbulent scouring leads to abrasive particle residence time; therefore, a flow rate of 200 mL / min was selected for further experimental investigation in the polishing process.

[0159] Table 4 Performance Test Parameters

[0160]

[0161] As can be seen from the data in Table 4, increasing the concentration of acidic substances will improve the material selectivity ratio (SiC:SiO2) and removal rate, but the surface roughness will also increase accordingly. Example 1 shows the electrochemical polishing conditions with the best performance in terms of removal rate, surface roughness and material selectivity ratio (SiC:SiO2).

[0162] Test Example 1

[0163] In this test case, the polished silicon carbide wafers of Example 1 and Comparative Example 1 were subjected to the following performance tests, and the performance of each item was compared. The data of removal rate, surface roughness Ra, subsurface damage layer, material selectivity ratio and energy consumption are summarized in Table 5.

[0164] Table 5 Performance Test Results

[0165]

[0166] As can be seen from the data in Table 5, the electrochemical mechanical polishing composition provided in this embodiment of the invention has significant performance advantages over the conventional composition in Comparative Example 1 when polishing silicon carbide wafers. The surface roughness Ra is reduced by 62.5%, the subsurface damage layer is completely eliminated, energy consumption is reduced by 55.6%, and the material selectivity is increased by 1900%.

[0167] Acidic ECMP achieves atomic-level surface treatment, zero damage, and high selectivity, upgrading the cleaning process from "passively removing contaminants" to "actively building anti-contamination surfaces."

[0168] When the surface roughness Ra is 0.03 nm, the physical adsorption barrier is increased, and the residue of particles / organic matter can be greatly reduced; the absence of an atomic damage layer can eliminate the masking effect of pollutants, and the metal ion removal rate approaches 100%; the material selection ratio of 20:1 indicates that it can be compatible with complex cleaning structures and ensure the reliability of advanced devices.

[0169] Ultimate benefits: In the era of sub-3nm processes and third-generation semiconductors, acidic ECMP reduces the yield loss in the cleaning process from 8% to less than 0.5%, while reducing overall costs by more than 40%.

[0170] In summary, the electrochemical mechanical polishing composition provided in this embodiment of the invention offers a simple and controllable process for polishing silicon carbide wafers. The ECMP polishing composition is an acidic environment system, free of heavy metals, and can be directly discharged after neutralization, resulting in low processing costs. Furthermore, the polishing process utilizes a "cathodic reduction reaction + mechanical" mechanism to achieve a polishing effect with minimal damage to silicon carbide wafers, even reaching zero damage, which is expected to further promote the development of silicon carbide semiconductor manufacturing.

[0171] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrochemical mechanical polishing composition, characterized in that, The electrochemical mechanical polishing composition comprises the following components: The first acidic substance at concentrations of 0.05 mol / L to 0.45 mol / L, the second acidic substance at concentrations of 0.01 mol / L to 0.25 mol / L, H₂O₂ at concentrations of 0.08 mol / L to 0.12 mol / L, and 0.2 kg / m 3 -1kg / m 3 abrasive grains; The first acidic substance is selected from at least one of phosphoric acid, sulfuric acid, aminosulfonic acid and oxalic acid; The second acidic substance is selected from at least one of ascorbic acid, isoascorbic acid, citric acid, tartaric acid, hydroxylamine hydrochloride, and malic acid; The abrasive particles are layered boron nitride with a particle size of 10nm-20nm.

2. The electrochemical mechanical polishing composition according to claim 1, characterized in that, The first acidic substance is 0.08 mol / L-0.12 mol / L phosphoric acid or 0.3 mol / L-0.4 mol / L oxalic acid; And / or, the second acidic substance is 0.018 mol / L-0.026 mol / L of ascorbic acid or 0.1 mol / L-0.2 mol / L of hydroxylamine hydrochloride.

3. The electrochemical mechanical polishing composition according to claim 1, characterized in that, The mass concentration of boron nitride is 0.4 kg / m³. 3 -0.6kg / m 3 .

4. The application of the electrochemical mechanical polishing composition as described in any one of claims 1-3 in the polishing of silicon carbide wafers.

5. A method for polishing silicon carbide wafers, characterized in that, Includes the following steps: Abrasive pretreatment, preparation of polishing slurry, polishing treatment, and post-treatment; wherein the polishing slurry comprises the electrochemical mechanical polishing composition as described in any one of claims 1-3; The abrasive pretreatment includes: heating boron nitride at 280℃-320℃ for 0.8h-1.5h, followed by immersion in TiCl4-ethanol solution for 25min-60min; The preparation of the polishing slurry includes: mixing the first acidic substance, the second acidic substance, H2O2 and abrasive particles evenly in proportion to obtain a polishing slurry with a Zeta potential > 40mV.

6. The method according to claim 5, characterized in that, In the abrasive pretreatment, the heat treatment is carried out in an N2 / H2O environment with a volume ratio of (3-8):

1.

7. The method according to claim 5, characterized in that, The polishing process involves a flow rate of 180 mL / min to 220 mL / min and a pressure of 0.3 N / cm. 2 -0.8N / cm 2 The rotation speed was 35 rpm to 60 rpm, and the temperature was 35℃ to 45℃. The removal rate of the softening layer material on the silicon carbide wafer surface was 380 nm / min to 450 nm / min.

8. The method according to claim 5, characterized in that, The post-processing includes abrasive grain recovery and uniform processing of silicon carbide wafers; The abrasive recycling process includes collecting the waste liquid after cleaning the polishing process.

9. A silicon carbide wafer, characterized in that, Prepared by the method described in any one of claims 5-8; The surface roughness of the silicon carbide wafer is 0.02nm-0.03nm, and the subsurface damage is 0; the material selection ratio of SiC:SiO2 is 15:1-20:1.

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