Polishing solution and application thereof

Abstract

The invention provides a polishing solution and application thereof. The polishing solution comprises an oxidizing agent, nitrate, cerium oxide particles, a dispersing agent, an anti-settling agent, a pH regulator and a surfactant. The shape of the cerium oxide particles comprises any one or a combination of at least two of a triangular prism shape, a spherical shape and a quadrangular prism shape; the average particle size of the cerium oxide particles is 20 nm to 2000 nm; the anti-settling agent comprises flaky particles. By optimizing the composition of the polishing solution, the surface quality of a polished workpiece is remarkably improved, scratches on the surface of the polished workpiece are reduced, and the polishing efficiency is high.

Description

Technical Field

[0001] The invention relates to the field of semiconductor integrated circuit manufacturing, specifically to the field of semiconductor device polishing, and in particular to a polishing liquid and application thereof. Background Art

[0002] With the development of emerging technologies such as electric vehicles and 5G communications, new substrates represented by gallium nitride and silicon carbide are gaining more and more attention. The third-generation semiconductors, represented by silicon carbide, have the characteristics of large bandgap, high breakdown electric field, high saturated electron drift velocity, and high thermal conductivity, especially in the high-voltage environment of 1200V, which has obvious advantages.

[0003] SiC substrate processing technology is an important foundation for the manufacture of semiconductor devices. The quality and precision of its surface processing directly affect the quality of epitaxial thin films and the performance of devices. It is usually required that the wafer surface be ultra-smooth, defect-free, damage-free, and the surface roughness be below nanometers. However, silicon carbide crystals have the characteristics of high hardness, high brittleness, good wear resistance, and good chemical stability, which makes the processing of silicon carbide wafers very difficult.

[0004] CN118562392A discloses a polishing liquid for silicon carbide substrates, which uses aluminum oxide as abrasive, ferrate as an oxidant, and trivalent soluble iron salt as a regulator to improve the polishing efficiency and polishing surface quality of the polishing liquid. The polishing liquid does not contain strong acid, does not corrode processing equipment, does not pollute the environment, has low cost, and can be stably stored for a long time, but its maximum polishing rate can only reach 0.71μm / h.

[0005] CN111303772A discloses an ultra-fast, low-loss silicon carbide substrate polishing liquid and a preparation method thereof, comprising an additive and a polishing base liquid, wherein the polishing base liquid comprises nano-diamond micropowder, a strong oxidant, a stabilizer, etc.; the additive comprises graphene, tungsten carbide, silica gel and titanium dioxide in a certain weight ratio; the additive of the invention has the effect of balancing the friction force during polishing on the polishing base liquid, so that the silicon carbide substrate will not have scratches or aggravated roughness due to the accelerated polishing speed during high-speed polishing, but the surface roughness can only reach below 1.5nm.

[0006] CN115975511A discloses a polishing liquid and a polishing liquid set for grinding a silicon carbide substrate, wherein the raw materials of the polishing liquid contain permanganate, grinding particles, metal salt additives and water, wherein, by mass percentage, the permanganate is 0.1%-50%, the grinding particles are 0.01%-30%, and the metal salt additive is 0.01%-10%, and the pH value of the polishing liquid is adjusted to less than 7 by a pH regulator, and the grinding particles contain cerium oxide. However, the removal rate of the polishing liquid disclosed in the patent can only reach 1.27μm / h, and the thinning rate of the silicon carbide substrate is not ideal.

[0007] The abrasive particles in the polishing liquid used in the prior art are either high-strength materials with a hardness exceeding or close to that of silicon carbide, such as aluminum oxide and nano-diamond. Although they can ensure a high removal efficiency on the surface of the silicon carbide substrate, they are prone to cause deep scratches on the surface of the silicon carbide substrate, making it difficult to complete the repair in the subsequent fine polishing process; or abrasive particles with slightly lower hardness, such as silicon oxide and cerium oxide, are used. Although they can improve the surface quality of the silicon carbide substrate after polishing, the removal efficiency of the silicon carbide substrate is difficult to meet.

[0008] Therefore, it is of great significance to provide a polishing liquid that can reduce scratches on the silicon carbide surface, improve the surface roughness of the silicon carbide, and have a higher silicon carbide substrate removal rate. Summary of the invention

[0009] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a polishing liquid and its application. The present invention optimizes the components in the polishing liquid, selects cerium oxide particles with a lower hardness than silicon carbide as abrasive particles, reduces scratches on the surface of silicon carbide after polishing, and significantly improves the surface quality of silicon carbide after polishing; through the synergistic effect of the dispersant and the anti-precipitation agent, the dispersibility and stability of the cerium oxide particles in the polishing liquid are guaranteed, the grinding performance of the cerium oxide particles is fully utilized, and the oxidizing effect of the oxidant is combined to oxidize silicon carbide into silicon oxide with lower hardness, greatly improving the removal rate of the silicon carbide substrate.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a polishing liquid, the polishing liquid comprising an oxidant, a nitrate, cerium oxide particles, a dispersant, an anti-precipitation agent, a pH adjuster and a surfactant;

[0012] The shape of the cerium oxide particles includes any one of triangular prism, sphere or quadrangular prism or a combination of at least two of them; the average particle size of the cerium oxide particles is 20nm-2000nm; the anti-precipitation agent includes flaky particles; the average size of the flaky particles in the length direction is 0.5μm-3μm, and the average size in the width direction is 0.5μm-3μm.

[0013] In the present invention, cerium oxide particles with a hardness lower than that of silicon carbide are selected as abrasive particles. The shape of the cerium oxide particles includes any one of triangular prism, spherical or quadrangular prism, or a combination of at least two of them. Typical but non-limiting combinations include a combination of triangular prism and spherical, a combination of quadrangular prism and triangular prism, or a combination of spherical and quadrangular prism.

[0014] Since the surface of the silicon carbide substrate presents porous stepped silicon oxide after oxidation, the shape of the cerium oxide particles has an important influence on the efficiency and quality of polishing. The tips of the triangular prism-shaped cerium oxide particles are more prominent. Based on their high efficiency in removing edges and corners, adding triangular prism-shaped cerium oxide particles to the polishing liquid can significantly improve the polishing efficiency of the substrate. Spherical cerium oxide particles have no edges and corners. Adding spherical cerium oxide particles to the polishing liquid can significantly improve the surface quality of the substrate after polishing. Quadrangular prism-shaped cerium oxide particles have a better removal effect on step-shaped silicon oxide to a certain extent. At the same time, because they have a flat surface, they can reduce the roughness of the surface of the silicon substrate after polishing. Using quadrangular prism-shaped cerium oxide particles in the polishing liquid can improve the substrate surface quality while improving the substrate processing efficiency.

[0015] The average particle size of the cerium oxide particles is 20nm-2000nm, for example, it can be 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1200nm, 1400nm, 1600nm, 1800nm ​​or 2000nm, including but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0016] In the present invention, when the cerium oxide particles are triangular prisms or quadrangular prisms, the average particle size refers to the average size of the longest side of the cerium oxide particles. When the cerium oxide particles are spherical, the average particle size refers to the average diameter of the cerium oxide particles.

[0017] Flaky particles are selected as anti-precipitation agents. On the one hand, the flaky particles act between the cerium oxide particles to maintain the dispersion of the cerium oxide particles and the stability of the polishing liquid, and prevent the polishing liquid from stratifying. On the other hand, the flaky particles can also be adsorbed on the surface of the cerium oxide particles and the surface of the silicon carbide substrate, further improving the scratches on the substrate during the polishing process and reducing scratches.

[0018] The average size of the flaky particles in the length direction is 0.5μm-3μm, for example, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm or 3μm, and the average size in the width direction is 0.5μm-3μm, for example, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm or 3μm, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. The thickness of the flaky particles used in the present invention is a single-digit molecular size and is not specifically limited. For example, the thickness of the flaky particles can be 1 nm-9 nm, for example, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm or 9 nm, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] The present invention optimizes the composition of the polishing liquid, selects cerium oxide particles of a specific shape and particle size as the grinding particles, and the dispersant and the anti-precipitation agent act on the surface of the cerium oxide particles and between the cerium oxide particles respectively, thereby avoiding the agglomeration of the cerium oxide particles and keeping the polishing liquid non-stratified for a long time, and jointly ensuring that the cerium oxide particles maintain a high degree of dispersion in the polishing liquid, which is conducive to fully exerting the grinding effect of the cerium oxide particles, and cooperates with the oxidation effect of the oxidant on the silicon carbide substrate, greatly improving the removal rate of the silicon carbide substrate, and significantly improving the surface quality of the workpiece after polishing, reducing scratches on the surface of the workpiece after polishing. In addition, the flaky particles can also be adsorbed on the surface of the cerium oxide particles and the silicon carbide substrate, further improving the scratches on the substrate during the polishing process, and reducing scratches.

[0020] Preferably, the plate-like particles include montmorillonite and / or bentonite.

[0021] Preferably, the cerium oxide particles include sintered cerium oxide particles and / or colloidal cerium oxide particles. Sintered cerium oxide particles have low cost, larger particle size, and higher silicon carbide substrate thinning rate, while colloidal particles can have smaller and more concentrated particle size, higher substrate surface quality after polishing, and correspondingly slower polishing rate.

[0022] Preferably, the average particle size of the cerium oxide particles is 30nm-1000nm, for example, it can be 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0023] Preferably, the polishing liquid comprises, in parts by weight:

[0024]

[0025]

[0026] The present invention does not impose any particular limitation on the solid content of the polishing liquid, and the solid content can be adaptively adjusted according to polishing requirements.

[0027] The weight proportion of the oxidant in the polishing liquid of the present invention is 1 part to 10 parts, for example, it can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] The weight proportion of cerium oxide particles in the polishing liquid of the present invention is 1.5-15 parts, for example, 1.5, 3, 4.5, 6, 7.5, 9, 10.5, 12, 13.5 or 15 parts, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] The weight proportion of the dispersant in the polishing liquid of the present invention is 0.25 parts to 2.5 parts, for example, it can be 0.25 parts, 0.5 parts, 0.75 parts, 1 parts, 1.25 parts, 1.5 parts, 1.75 parts, 2 parts, 2.25 parts or 2.5 parts, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] The weight proportion of the anti-precipitation agent in the polishing liquid of the present invention is 0.25 parts to 2.5 parts, for example, it can be 0.25 parts, 0.5 parts, 0.75 parts, 1 parts, 1.25 parts, 1.5 parts, 1.75 parts, 2 parts, 2.25 parts or 2.5 parts, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] The weight proportion of the surfactant in the polishing liquid of the present invention is 0.025-0.25 parts, for example, it can be 0.025 parts, 0.05 parts, 0.075 parts, 0.1 parts, 0.125 parts, 0.15 parts, 0.175 parts, 0.2 parts, 0.225 parts or 0.25 parts, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] The weight proportion of water in the polishing liquid of the present invention is 60-100 parts, for example, it can be 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts or 100 parts, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Preferably, the nitrate comprises any one of sodium nitrate, potassium nitrate, ammonium nitrate, calcium nitrate, magnesium nitrate, aluminum nitrate, iron nitrate, cobalt nitrate, copper nitrate, zinc nitrate or silver nitrate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of magnesium nitrate and aluminum nitrate, a combination of copper nitrate and magnesium nitrate, a combination of aluminum nitrate and copper nitrate, a combination of copper nitrate and sodium nitrate, a combination of copper nitrate and ammonium nitrate, a combination of copper nitrate and cobalt nitrate, or a combination of copper nitrate and zinc nitrate.

[0034] Preferably, the nitrate comprises any one of magnesium nitrate, aluminum nitrate or copper nitrate or a combination of at least two thereof, preferably copper nitrate.

[0035] Preferably, the oxidant comprises any one of potassium permanganate, sodium permanganate, potassium perchlorate, potassium chlorate, potassium periodate, sodium periodate, hydrogen peroxide or potassium persulfate, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of potassium permanganate and sodium permanganate, a combination of potassium perchlorate and potassium chlorate, a combination of potassium periodate and sodium periodate, or a combination of hydrogen peroxide and potassium persulfate.

[0036] Preferably, the oxidant is potassium permanganate and / or sodium permanganate.

[0037] Preferably, the oxidant is potassium permanganate.

[0038] Adding a dispersant into the polishing liquid can make the cerium oxide particles in the polishing liquid evenly distributed in the polishing liquid, thereby ensuring the consistency of the grinding efficiency throughout the polishing process.

[0039] Preferably, the dispersant includes any one of sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate, alkyl aryl phosphates, alkylbenzene sulfonates, dialkyl sulfosuccinates, trimethyl stearamide chloride or polyoxyethylene alkylphenol ether, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of sodium hexametaphosphate and sodium pyrophosphate, a combination of sodium tripolyphosphate and alkyl aryl phosphates, a combination of alkylbenzene sulfonates and dialkyl sulfosuccinates, or a combination of trimethyl stearamide chloride and polyoxyethylene alkylphenol ether.

[0040] Preferably, the surfactant includes any one of cetyltrimethylammonium bromide, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium perfluorononenyloxybenzene sulfonate, sodium polyacrylate, and 2-acrylamide-2-methylpropane sulfonic acid, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of cetyltrimethylammonium bromide and sodium dodecylbenzene sulfonate, a combination of sodium dodecyl sulfate and sodium perfluorononenyloxybenzene sulfonate, or a combination of sodium polyacrylate and 2-acrylamide-2-methylpropane sulfonic acid.

[0041] Preferably, the surfactant comprises sodium carboxymethyl cellulose and / or sodium perfluorononenyloxybenzene sulfonate.

[0042] Preferably, the pH of the polishing liquid is 3.5-6.5, for example, the pH of the polishing liquid may be 3.5, 4, 4.5, 5, 5.5, 6 or 6.5, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the pH adjuster is an inorganic acid.

[0044] Preferably, the pH adjuster comprises any one of hydrochloric acid, nitric acid, sulfuric acid or phosphoric acid, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of hydrochloric acid and nitric acid, a combination of sulfuric acid and phosphoric acid, a combination of nitric acid and sulfuric acid, or a combination of phosphoric acid and hydrochloric acid, preferably nitric acid.

[0045] The polishing liquid provided by the present invention can be prepared by conventional methods in the art without any particular limitation. For example, the polishing liquid can be obtained by mixing the components of the polishing liquid in the present application according to specific mass parts and aging them.

[0046] In a second aspect, the present invention provides an application of the polishing liquid as described in the first aspect, wherein the polishing liquid is applied to polishing of semiconductor devices, for example, applied to polishing of silicon carbide substrates.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention optimizes the components in the polishing liquid, selects cerium oxide particles with a lower hardness than silicon carbide as abrasive particles, reduces scratches on the surface of silicon carbide after polishing, and significantly improves the surface quality of silicon carbide after polishing. The synergistic effect of the dispersant and the anti-precipitation agent ensures the dispersibility and stability of the cerium oxide particles in the polishing liquid, and cooperates with the oxidizing effect of the oxidant to greatly improve the removal rate of the silicon carbide substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a SEM image of the cerium oxide particles used in the polishing liquid in Example 1.

[0050] Figure 2 This is a SEM image of the cerium oxide particles used in the polishing liquid in Example 2.

[0051] Figure 3 This is a SEM image of the cerium oxide particles used in the polishing liquid in Example 3.

[0052] Figure 4 This is a SEM image of the cerium oxide particles used in the polishing liquid in Example 4.

[0053] Figure 5 This is a SEM image of the cerium oxide particles used in the polishing liquid in Example 5.

[0054] Figure 6 This is a SEM image of the cerium oxide particles used in the polishing liquid in Example 6.

[0055] Figure 7 This is an AFM image of the silicon carbide surface after polishing with the polishing liquid in Example 1.

[0056] Figure 8 This is an AFM image of the silicon carbide surface after polishing with the polishing liquid in Example 2.

[0057] Fig. 9 This is an AFM image of the silicon carbide surface after polishing with the polishing liquid in Example 3.

[0058] Fig.10 This is an AFM image of the silicon carbide surface after polishing with the polishing liquid in Example 4.

[0059] Fig.11 This is an AFM image of the silicon carbide surface after polishing with the polishing liquid in Example 5.

[0060] Fig.12 This is an AFM image of the silicon carbide surface after polishing with the polishing liquid in Example 6. DETAILED DESCRIPTION

[0061] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0062] Example 1

[0063] The present embodiment provides a polishing liquid, and the preparation method of the polishing liquid includes mixing 2 parts by weight of potassium permanganate, 1 part by weight of copper nitrate, 3 parts by weight of cerium oxide particles, 0.5 parts by weight of sodium hexametaphosphate, 0.5 parts by weight of montmorillonite, 0.05 parts by weight of sodium dodecylbenzene sulfonate and 80 parts by weight of water, and adjusting the pH of the mixed solution to 4 with nitric acid, aging for 40 minutes, to prepare the polishing liquid.

[0064] In this embodiment, the particle size of the cerium oxide particles is 100 nm, and the shape is triangular prism. The average size of the montmorillonite in the length direction is 1 μm, the average size in the width direction is 1 μm, and the thickness is 6 nm.

[0065] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 1 shown.

[0066] Example 2

[0067] The present embodiment provides a polishing liquid, and the preparation method of the polishing liquid includes mixing 1.5 parts by weight of sodium permanganate, 1 part by weight of aluminum nitrate, 1.55 parts by weight of cerium oxide particles, 0.25 parts by weight of sodium pyrophosphate, 0.8 parts by weight of bentonite, 0.025 parts by weight of sodium carboxymethyl cellulose and 100 parts by weight of water, and adjusting the pH of the mixed solution to 3.5 with hydrochloric acid, aging for 45 minutes, to prepare the polishing liquid.

[0068] In this embodiment, the particle size of the cerium oxide particles is 100 nm, and the shape is quadrangular prism. The average size of the bentonite in the length direction is 1 μm, the average size in the width direction is 1 μm, and the thickness is 4 nm.

[0069] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 2 shown.

[0070] Example 3

[0071] The present embodiment provides a polishing liquid, and the preparation method of the polishing liquid comprises mixing 5 parts by weight of potassium persulfate, 1 part by weight of magnesium nitrate, 7 parts by weight of cerium oxide particles, 1 part by weight of polyoxyethylene alkylphenol ether, 1.5 parts by weight of montmorillonite, 0.1 parts by weight of sodium perfluorononenyloxybenzene sulfonate and 70 parts by weight of water, and adjusting the pH of the mixed solution to 3.8 with phosphoric acid, and aging for 40 minutes to prepare the polishing liquid.

[0072] In this embodiment, the particle size of the cerium oxide particles is 100 nm and the shape is spherical. The average size of the montmorillonite in the length direction is 1 μm, the average size in the width direction is 1 μm, and the thickness is 2 nm.

[0073] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 3 shown.

[0074] Example 4

[0075] The present embodiment provides a polishing liquid, and the preparation method of the polishing liquid includes mixing 7 parts by weight of potassium permanganate, 1 part by weight of potassium nitrate, 8 parts by weight of cerium oxide particles, 1.5 parts by weight of sodium hexametaphosphate, 2 parts by weight of montmorillonite, 0.12 parts by weight of sodium dodecylbenzene sulfonate and 80 parts by weight of water, and adjusting the pH of the mixed solution to 4.5 with nitric acid, aging for 50 minutes, to prepare the polishing liquid.

[0076] In this embodiment, the particle size of the cerium oxide particles is 200 nm, and the shape is triangular prism. The average size of the montmorillonite in the length direction is 2 μm, the average size in the width direction is 2 μm, and the thickness is 9 nm.

[0077] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 4 shown.

[0078] Example 5

[0079] The present embodiment provides a polishing liquid, and the preparation method of the polishing liquid includes mixing 8 parts by weight of potassium permanganate, 1 part by weight of copper nitrate, 12 parts by weight of cerium oxide particles, 2 parts by weight of sodium hexametaphosphate, 2.2 parts by weight of montmorillonite, 0.2 parts by weight of sodium dodecylbenzene sulfonate and 90 parts by weight of water, and adjusting the pH of the mixed solution to 4 with nitric acid, aging for 40 minutes, to prepare the polishing liquid.

[0080] In this embodiment, the particle size of the cerium oxide particles is 200 nm, and the shape is quadrangular prism. The average size of the montmorillonite in the length direction is 3 μm, the average size in the width direction is 2 μm, and the thickness is 7 nm.

[0081] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 5 shown.

[0082] Example 6

[0083] The present embodiment provides a polishing liquid, and the preparation method of the polishing liquid includes mixing 8 parts by weight of potassium permanganate, 1 part by weight of copper nitrate, 15 parts by weight of cerium oxide particles, 2.5 parts by weight of sodium hexametaphosphate, 2.5 parts by weight of montmorillonite, 0.25 parts by weight of sodium dodecylbenzene sulfonate and 60 parts by weight of water, and adjusting the pH of the mixed solution to 4 with nitric acid, aging for 40 minutes, to prepare the polishing liquid.

[0084] In this embodiment, the particle size of the cerium oxide particles is 200 nm and the shape is spherical. The average size of the montmorillonite in the length direction is 3 μm, the average size in the width direction is 3 μm, and the thickness is 6 nm.

[0085] The SEM image of the cerium oxide particles in this embodiment is as follows: Figure 6 shown.

[0086] Example 7

[0087] This embodiment provides a polishing liquid, which is the same as that of Embodiment 1 except that the particle size of the cerium oxide particles is 30 nm.

[0088] Example 8

[0089] This embodiment provides a polishing liquid, which is the same as that of Embodiment 1 except that the particle size of the cerium oxide particles is 1000 nm.

[0090] Example 9

[0091] This embodiment provides a polishing liquid, which is the same as that of Embodiment 1 except that the mass fraction of cerium oxide particles is adjusted to 0.5 parts.

[0092] Example 10

[0093] This embodiment provides a polishing liquid, which is the same as that of Embodiment 1 except that the mass fraction of cerium oxide particles is adjusted to 20 parts.

[0094] Embodiment 11

[0095] This embodiment provides a polishing liquid, which is the same as that of Embodiment 1 except that the mass portion of montmorillonite is adjusted to 0.1 parts.

[0096] Example 12

[0097] This embodiment provides a polishing liquid, which is the same as that of Embodiment 1 except that the mass fraction of montmorillonite is adjusted to 5 parts.

[0098] Embodiment 13

[0099] This embodiment provides a polishing liquid, which is the same as that of Embodiment 1 except that the mass fraction of sodium hexametaphosphate is adjusted to 0.1 parts.

[0100] Embodiment 14

[0101] This embodiment provides a polishing liquid, which is the same as that of Embodiment 1 except that the mass fraction of sodium hexametaphosphate is adjusted to 3.5 parts.

[0102] Comparative Example 1

[0103] This comparative example provides a polishing liquid, which is the same as Example 1 except that the average size of the montmorillonite in the length direction is 0.5 μm and the average size in the width direction is 0.2 μm.

[0104] Comparative Example 2

[0105] This comparative example provides a polishing liquid, which is the same as Example 1 except that the average size of the montmorillonite in the length direction is 5 μm and the average size in the width direction is 5 μm.

[0106] Comparative Example 3

[0107] This comparative example provides a polishing liquid, which is the same as Example 1 except that the particle size of the cerium oxide particles is 10 nm.

[0108] Comparative Example 4

[0109] This comparative example provides a polishing liquid, which is the same as Example 1 except that the particle size of the cerium oxide particles is 3000 nm.

[0110] Comparative Example 5

[0111] This comparative example provides a polishing liquid, which is the same as Example 1 except that the montmorillonite is replaced by an equal weight portion of a fumed silica-modified polyurea solution in N-methylpyrrolidone.

[0112] Comparative Example 6

[0113] This comparative example provides a polishing liquid, which is the same as Example 1 except that montmorillonite is not added.

[0114] Comparative Example 7

[0115] This comparative example provides a polishing liquid, which is the same as Example 1 except that sodium hexametaphosphate is not added.

[0116] Performance Test:

[0117] The polishing experiment was carried out using a 16B machine produced by Mingzheng Electronic Assembly Co., Ltd. The polishing substrate was 6-inch 4H-SiC, the polishing pad was SUBA800, the polishing pressure was 500kg, the polishing speed was 35rmp, the polishing liquid flow rate was 1200ml, the polishing time was 1h, and the polishing experiment was carried out at room temperature. After polishing, the silicon carbide substrate was washed with water for 3 minutes and then dried with nitrogen. The thickness and surface roughness were measured respectively. The test results are shown in Table 1. The AFM images of the silicon carbide surface after polishing with the polishing liquid in Examples 1 to 6 are shown in Table 1. Figure 7-Figure 12 shown.

[0118] Table 1

[0119]

[0120]

[0121] According to the test results of Examples 1 to 8, it can be determined that the present invention optimizes the components in the polishing liquid, selects cerium oxide particles with a hardness lower than that of silicon carbide as abrasive particles, and ensures the dispersibility and stability of cerium oxide particles in the polishing liquid under the joint action of the dispersant and the anti-precipitation agent, and cooperates with the oxidizing action of the oxidant to greatly improve the removal rate of the silicon carbide substrate, and reduce the scratches on the surface of the silicon carbide after polishing, and the surface quality of the silicon carbide after polishing is significantly improved. The polishing liquid provided by the present invention can achieve a removal rate of more than 1.8 μm / h for the silicon carbide substrate. When 1000nm triangular prism-shaped cerium oxide particles are selected in Example 8, the removal rate of the silicon carbide substrate can even be as high as 7.1 μm / h. When 200nm quadrangular prism-shaped cerium oxide particles are selected in Example 5, the removal rate of the silicon carbide substrate can reach 3.7 μm / h, and only individual scratches exist, and the roughness is as low as 0.0847nm. The polishing liquid provided by the present invention only needs to make slight adjustments to the components and select the shape of the cerium oxide particles to meet the needs of many application scenarios such as high requirements for the removal rate of the silicon carbide substrate or high requirements for the quality of the silicon carbide substrate after polishing.

[0122] According to the test results of Example 1 and Example 9-Example 10, the mass fraction of cerium oxide particles affects the removal rate of silicon dioxide after oxidation of the silicon carbide substrate, and the removal rate should match the oxidation rate. When the oxidation rate is constant, after the removal rate of the silicon carbide substrate reaches saturation, even if the mass fraction of cerium oxide particles is increased, the removal efficiency of the silicon carbide substrate cannot be further improved. If the mass fraction of cerium oxide particles is too small, the removal rate of silicon dioxide, an oxidation product on the surface of silicon carbide, is lower than the oxidation rate of the silicon carbide substrate, resulting in the inability to remove silicon dioxide in time and leaving scratches.

[0123] According to the test results of Example 1 and Example 11-Example 12, the mass fraction of montmorillonite affects the uniform distribution of cerium oxide particles in the polishing liquid and the viscosity of the polishing liquid. If the mass fraction of the whole montmorillonite is too large, the viscosity of the polishing liquid will be too large and the flow rate of the polishing liquid will be too slow, which will greatly hinder the polishing rate. If the mass fraction of the whole montmorillonite is too small, the cerium oxide particles in the polishing liquid will settle too quickly, the efficiency of the action will be unstable during the polishing process, and scratches will appear on the surface of the substrate after processing.

[0124] According to the test results of Example 1 and Example 13-Example 14, the mass fraction of the dispersant affects the polishing effect. If the mass fraction of the dispersant is too large, the excessive amount of dispersant will also cause the double electric layer of the cerium oxide particles to be compressed, the cerium oxide particles to agglomerate, and the stability of the polishing liquid system to be destroyed, which greatly inhibits the polishing rate. If the mass fraction of the dispersant is too small, the dispersion repulsion applied between the cerium oxide particles will be too small, which will also cause the cerium oxide particles to agglomerate. Too much or too little mass fraction of the dispersant will deteriorate the polishing effect.

[0125] According to the test results of Example 1 and Comparative Examples 1-2, the average size of the anti-precipitation agent flaky particles affects the polishing effect. If the average size of the flaky particles in the length and width directions is too large, that is, the surface area of ​​the flaky particles is too large, they will adhere to the substrate surface, hindering the oxidation efficiency and the removal efficiency of silicon dioxide after oxidation of the silicon carbide substrate; if the surface area of ​​the flaky particles is too large or too small, they cannot provide sufficient protection for the substrate surface, resulting in scratches on the substrate surface after processing.

[0126] According to the test results of Example 1 and Comparative Examples 3 and 4, the particle size of cerium oxide particles affects the polishing rate and roughness. If the particle size of cerium oxide particles is too small, the polishing rate is too slow. If the particle size of cerium oxide particles is too large, the surface quality of the substrate is deteriorated.

[0127] According to the test results of Example 1 and Comparative Example 5, if the anti-precipitation agent is replaced with the N-methylpyrrolidone solution of fumed silica-modified polyurea used in the prior art, the stability of the polishing liquid deteriorates, and the scratches on the substrate during the polishing process cannot be improved, and the scratches on the substrate surface increase.

[0128] According to the test results of Example 1 and Comparative Example 6, if the anti-precipitation agent is not added, the stability of the polishing liquid deteriorates, and the scratches on the substrate during the polishing process cannot be improved, and the scratches on the substrate surface increase.

[0129] According to the test results of Example 1 and Comparative Example 7, if no dispersant is added, the cerium oxide particles cannot be evenly distributed in the polishing liquid, the polishing liquid appears sandy, and the polishing test cannot be performed.

[0130] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polishing liquid, characterized in that: The polishing liquid comprises an oxidant, a nitrate, cerium oxide particles, a dispersant, an anti-precipitation agent, a pH regulator and a surfactant; The shape of the cerium oxide particles includes any one of a triangular prism, a sphere or a quadrangular prism, or a combination of at least two of them; the average particle size of the cerium oxide particles is 20nm-2000nm; The anti-precipitation agent comprises flaky particles; the average size of the flaky particles in the length direction is 0.5 μm-3 μm, and the average size in the width direction is 0.5 μm-3 μm.

2. The polishing liquid according to claim 1, characterized in that The flaky particles include montmorillonite and / or bentonite.

3. The polishing liquid according to claim 1, characterized in that The cerium oxide particles include sintered cerium oxide particles and / or colloidal cerium oxide particles.

4. The polishing liquid according to claim 1, characterized in that In parts by weight, the polishing liquid comprises:

5. The polishing liquid according to claim 1, characterized in that The nitrate includes any one of sodium nitrate, potassium nitrate, ammonium nitrate, calcium nitrate, magnesium nitrate, aluminum nitrate, iron nitrate, cobalt nitrate, copper nitrate, zinc nitrate or silver nitrate, or a combination of at least two thereof.

6. The polishing liquid according to claim 1, characterized in that The oxidant includes any one of potassium permanganate, sodium permanganate, potassium perchlorate, potassium chlorate, potassium periodate, sodium periodate, hydrogen peroxide or potassium persulfate, or a combination of at least two thereof.

7. The polishing liquid according to claim 1, characterized in that The dispersant includes any one of sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate, alkyl aryl phosphate, alkyl benzene sulfonate, dialkyl sulfosuccinate, trimethyl stearamide chloride or polyoxyethylene alkylphenol ether, or a combination of at least two thereof.

8. The polishing liquid according to claim 1, characterized in that The surfactant includes any one of cetyltrimethylammonium bromide, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium perfluorononenyloxybenzene sulfonate, sodium polyacrylate, sodium carboxymethyl cellulose, and 2-acrylamide-2-methylpropane sulfonic acid, or a combination of at least two thereof.

9. The polishing liquid according to claim 1, characterized in that The pH of the polishing liquid is 3.5-6.5, and the pH adjuster includes any one of hydrochloric acid, nitric acid, sulfuric acid or phosphoric acid, or a combination of at least two of them.

10. A use of the polishing liquid according to any one of claims 1 to 9, characterized in that: The polishing liquid is used for polishing semiconductor devices.

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