Silicon carbide polishing solution containing composite silica sol abrasive as well as preparation method and application of silicon carbide polishing solution

Abstract

The invention relates to the technical field of material processing, in particular to a silicon carbide polishing solution containing a composite silica sol abrasive as well as a preparation method and application of the silicon carbide polishing solution. The silicon carbide polishing solution containing the composite silica sol abrasive comprises the following components in percentage by mass: 1%-20% of the composite silica sol abrasive, 0.01%-1% of a dispersing agent, 0.1%-10% of an oxidizing agent, 1%-20% of an auxiliary oxidizing agent, 0.001%-0.1% of a pH regulator and the balance of deionized water, the composite silica sol abrasive material comprises at least two kinds of silica sol with the particle size difference being 50 nm or above. Silica sol with different particle sizes is adopted to prepare the irregular composite abrasive material, the irregular composite abrasive material is matched with various assistants to improve the dual effects of chemical oxidation and mechanical friction, the mechanical friction point and wear resistance of the silicon carbide polishing solution can be enhanced, meanwhile, surface scratches and damaged layers of wafers are not prone to being caused in the polishing process, and the surface roughness is low.

Description

Technical Field

[0001] The invention relates to the technical field of material processing, in particular to a silicon carbide polishing liquid containing composite silica sol abrasive, and a preparation method and application thereof. Background Art

[0002] With the rapid growth of demand for high-frequency, high-power radio frequency and power electronics such as 5G and new energy, the third-generation semiconductor materials led by silicon carbide are gradually entering large-scale applications and moving towards industrialization under this trend. The processing quality and precision of silicon carbide substrates will directly affect the performance of the device. Chemical mechanical polishing (CMP) has been considered to be one of the most effective methods to achieve global flattening and ultra-smooth surfaces. The polishing liquid usually uses high-hardness abrasives such as diamond micropowder and aluminum oxide particles. Although the strong mechanical action can increase the rate, it is very easy to form microcracks, scratches, and sub-surface damage layers, resulting in low yield of the finished product. In the prior art, the polishing liquid of aluminum oxide and cerium oxide systems generally has many defects on the wafer surface after polishing, the roughness cannot meet the requirements, and the wafer yield is low. It is difficult to achieve the best dynamic balance between chemical reaction and mechanical friction. When the mechanical action of the polishing liquid abrasive is too strong, it can easily cause surface scratches, sub-surface damage, and excessive roughness. If the chemical action is too strong, the oxidation rate of the wafer surface will be too fast. The residual softened layer cannot be polished away in time, and defects such as "orange peel" and pits will appear on the substrate surface, which are difficult to repair.

[0003] The existing fine polishing liquid using silica sol as abrasive has the problems of low polishing rate, long processing time, and difficulty in removing grinding damage caused by previous processing. At the same time, the fine polishing liquid of the silica sol system is easy to crystallize and precipitate, which is difficult to store and reduces the service life.

[0004] In view of the above problems, it is of great significance to develop an efficient and stable fine polishing liquid that can obtain excellent roughness, have both polishing surface quality and polishing efficiency, and reduce processing costs. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention adopts silica sols of different particle sizes to prepare irregular composite abrasives, and cooperates with various additives to enhance the dual effects of chemical oxidation and mechanical friction, thereby obtaining a fine polishing liquid with high polishing efficiency and high flattening treatment.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a silicon carbide polishing liquid containing a composite silica sol abrasive, comprising the following components in mass percentage: 1%-20% composite silica sol abrasive, 0.01%-1% dispersant, 0.1%-10% oxidant, 1%-20% auxiliary oxidant, 0.001%-0.1% pH adjuster, and the rest is deionized water; the composite silica sol abrasive comprises at least two silica sols with a particle size difference of more than 50nm.

[0008] In some embodiments of the present invention, the particle size of the silica sol is 15-130 nm.

[0009] In some embodiments of the present invention, the pH value of the silicon carbide polishing liquid is 6.0-7.0.

[0010] In some embodiments of the present invention, based on the total mass of the composite silica sol abrasive, the composite silica sol abrasive is composed of 30%-88% of silica sol with a particle size of 80 nm and 12%-70% of silica sol with a particle size of 130 nm; the mass proportion of the dispersant in the silicon carbide polishing liquid is 0.1%.

[0011] In some embodiments of the present invention, based on the total mass of the composite silica sol abrasive, the composite silica sol abrasive is composed of 2%-25% of silica sol with a particle size of 15 nm, 30%-75% of silica sol with a particle size of 80 nm and 12%-63% of silica sol with a particle size of 130 nm; the mass proportion of the dispersant in the silicon carbide polishing liquid is 0.5%.

[0012] The second aspect of the present invention provides a method for preparing the silicon carbide polishing liquid containing the composite silica sol abrasive, comprising the following steps:

[0013] Step 1: Evenly mix silica sols of different particle sizes to obtain composite silica sol abrasive;

[0014] Step 2: Add dispersant, oxidant, auxiliary oxidant and deionized water to the composite silica sol abrasive in sequence, mix well, add pH adjuster to adjust the pH to 6.0-7.0, and obtain silicon carbide polishing liquid.

[0015] The third aspect of the present invention provides the use of the silicon carbide polishing liquid containing the composite silica sol abrasive in chemical mechanical polishing.

[0016] In some embodiments of the present invention, the present invention is applicable to silicon carbide wafer polishing.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The silicon carbide polishing liquid containing composite silica sol abrasive provided by the present invention enhances the friction effect of polishing at a specific ratio by mixing silica sols of different particle sizes, has both polishing rate and high surface quality, optimizes the composite abrasive, and selects the silica sol at the best compounding ratio to prepare the silicon carbide polishing liquid, controls the slight coagulation degree of the abrasive under the composite particle size, ensures that the silica sol is uniform and non-gelled, forms irregular linear and chain-shaped silica sols, and effectively increases the interface friction coefficient during the polishing process. A quantitative regulator is added in coordination to form a dispersed and uniform composite abrasive polishing liquid, which greatly improves the polishing efficiency.

[0019] 2. The silicon carbide polishing liquid containing composite silica sol abrasive provided by the present invention optimizes and screens the amount of dispersant used so that the composite silica sol abrasive is evenly dispersed, and at the same time cooperates with the chemical oxidation action of the oxidant and the co-oxidant to form a composite abrasive polishing liquid, thereby greatly improving the polishing efficiency.

[0020] 3. Compared with single abrasive silicon carbide polishing liquid, the silicon carbide polishing liquid provided by the present invention contains composite particle size silica sol abrasive, which can enhance the mechanical friction point and wear resistance of the silicon carbide polishing liquid. At the same time, the polishing process is not easy to cause scratches and damage layers on the wafer surface, and the surface roughness is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM image of the silicon carbide polishing liquid containing composite silica sol abrasive provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0022] The silicon carbide polishing liquid containing composite silica sol abrasive of the present invention and its preparation method and application are described in detail below.

[0023] The inventors of the present invention enhanced the friction effect of polishing by preparing silica sols of different particle sizes at a specific ratio, and synergistically added a specific amount of dispersant to control the slight degree of agglomeration of the abrasive under the composite particle size to form irregular linear and chain-shaped silica sols, and adjusted the pH range of the polishing liquid. The above characteristics exerted a synergistic effect, and the friction coefficient of the polishing liquid at the silicon carbide interface was significantly improved. On this basis, the present invention was completed.

[0024] The first aspect of the present invention provides a silicon carbide polishing liquid containing a composite silica sol abrasive, comprising the following components in mass percentage: 1%-20% composite silica sol abrasive, 0.01%-1% dispersant, 0.1%-10% oxidant, 1%-20% auxiliary oxidant, 0.001%-0.1% pH adjuster, and the rest is deionized water; the composite silica sol abrasive comprises at least two silica sols with a particle size difference of more than 50nm.

[0025] The hardness of silica sol abrasive is less than that of diamond powder and alumina abrasive, and it has certain advantages in the fine polishing stage of silicon carbide. The particle size of silica sol will significantly affect the polishing efficiency. The particle size of the polishing liquid abrasive will affect the mechanical effect of polishing. Large-particle abrasives have a larger contact friction area and a relatively strong mechanical removal effect, while small-particle abrasives can refine the surface and improve the flatness, and can obtain a better polishing surface quality, but the polishing efficiency is low. Therefore, the synergistic effect of silica sols with different particle sizes is crucial to improving the polishing efficiency. The particle size range of silica sols currently available on the market is 20-160nm. The present invention forms an irregular composite abrasive by formulating silica sols with a particle size difference of more than 50nm, enhances the friction effect of polishing at a specific ratio, and cooperates with various additives to improve the dual effects of chemical oxidation and mechanical friction, thereby obtaining a fine polishing liquid with high polishing efficiency and high flattening treatment. In the present invention, the particle size of the silica sol is 15-130nm. The composite silica sol abrasive includes at least two silica sols with a particle size difference of more than 50nm, for example, two particle sizes including 15nm and 80nm, two particle sizes including 15nm and 130nm, two particle sizes including 80nm and 130nm, three particle sizes including 15nm, 80nm and 130nm, and so on.

[0026] In some specific embodiments of the present invention, the pH of the silicon carbide polishing liquid is 6.0-7.0, 6.0-6.5, or 6.5-7.0. In the present invention, the stability of the polishing liquid can be improved by controlling the pH of the silicon carbide polishing liquid to be weakly acidic.

[0027] In some specific embodiments of the present invention, based on the total mass of the composite silica sol abrasive, the composite silica sol abrasive consists of 30%-88% of silica sol with a particle size of 80 nm and 12%-70% of silica sol with a particle size of 130 nm.

[0028] In some specific embodiments of the present invention, based on the total mass of the composite silica sol abrasive, the composite silica sol abrasive is composed of 2%-25% of silica sol with a particle size of 15 nm, 30%-75% of silica sol with a particle size of 80 nm and 12%-63% of silica sol with a particle size of 130 nm.

[0029] In some specific embodiments of the present invention, the abrasive is spherical silica sol; in the present invention, the silica sol is prepared by an ion exchange method, a sol-gel method or a sodium silicate hydrolysis method.

[0030] In some specific embodiments of the present invention, the dispersant is selected from any one or more of sodium hexametaphosphate, sodium tripolyphosphate, and sodium polyacrylate. Preferably, the dispersant is selected from sodium hexametaphosphate. The dispersion stability of the composite silica sol abrasive in the silicon carbide polishing solution is a key factor affecting the quality of the polished surface and long-term storage. During the polishing process, the small-particle silica sol fills the gaps between the large-particle silica sols, making it easier for the silica sols to flocculate and gel. The present invention optimizes and screens the content of the dispersant to ensure that the composite silica sol is not easy to gel and improve the stability of the polishing solution. In some preferred embodiments of the present invention, based on the total mass of the composite silica sol abrasive, the composite silica sol abrasive is composed of 30%-88% of silica sol with a particle size of 80nm and 12%-70% of silica sol with a particle size of 130nm; the mass proportion of the dispersant in the silicon carbide polishing solution is 0.1%. In some other preferred embodiments of the present invention, based on the total mass of the composite silica sol abrasive, the composite silica sol abrasive is composed of 2%-25% of silica sol with a particle size of 15 nm, 30%-75% of silica sol with a particle size of 80 nm and 12%-63% of silica sol with a particle size of 130 nm; the mass proportion of the dispersant in the silicon carbide polishing liquid is 0.5%.

[0031] In some specific embodiments of the present invention, the oxidant is selected from any one or more of sodium metavanadate, sodium orthovanadate, potassium metavanadate, potassium orthovanadate, ammonium metavanadate, potassium molybdate, sodium molybdate, and ammonium molybdate. Preferably, the oxidant is selected from sodium metavanadate.

[0032] In some specific embodiments of the present invention, the auxiliary oxidant is selected from any one or more of hydrogen peroxide, potassium permanganate, potassium manganate, potassium ferrate, sodium periodate, iodic acid, and potassium iodate. Preferably, the auxiliary oxidant is selected from hydrogen peroxide. In some more specific embodiments of the present invention, the auxiliary oxidant is an aqueous solution of hydrogen peroxide. Since the addition of composite particle size silica sol improves the mechanical polishing performance, hydrogen peroxide is beneficial to improve the chemical oxidation corrosion of the silicon carbide surface and the polishing liquid, thereby obtaining the best flatness surface.

[0033] In some specific embodiments of the present invention, the pH regulator is selected from any one or more of nitric acid, sulfuric acid, citric acid, malic acid, tartaric acid, oxalic acid, acetic acid, potassium hydroxide, sodium hydroxide, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate. By adding the pH regulator, the pH of the polishing liquid is stabilized at 6.0-7.0, the decomposition of the auxiliary oxidant hydrogen peroxide is slowed down under weakly acidic conditions, and the circulation service life of the fine polishing liquid is increased.

[0034] The second aspect of the present invention provides a method for preparing the silicon carbide polishing liquid containing the composite silica sol abrasive, comprising the following steps:

[0035] Step 1: Evenly mix silica sols of different particle sizes to obtain composite silica sol abrasive;

[0036] Step 2: Add dispersant, oxidant, auxiliary oxidant and deionized water to the composite silica sol abrasive in sequence, mix well, add pH adjuster to adjust the pH to 6.0-7.0, and obtain silicon carbide polishing liquid.

[0037] In some specific embodiments of the present invention, the uniform mixing is achieved by mechanical stirring.

[0038] The third aspect of the present invention provides the use of the silicon carbide polishing liquid containing the composite silica sol abrasive in chemical mechanical polishing. The silicon carbide polishing liquid provided by the present invention has an optimal friction coefficient and removal rate with the silicon carbide surface, and the removal rate on the silicon surface can reach 230nm / h. At the same time, the surface roughness Ra after polishing can be reduced to less than 0.1nm, the substrate surface quality is high, the surface is free of scratches, and no organic matter remains. The polishing liquid has a long cycle life and high economic benefits.

[0039] In some specific embodiments of the present invention, the present invention is applicable to polishing silicon carbide wafers.

[0040] The specific embodiments of the present invention are further described in detail below in conjunction with preferred embodiments. When the embodiments provide numerical ranges, it should be understood that, unless otherwise specified in the present invention, the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, as those skilled in the art grasp the prior art and record the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention can also be used to realize the present invention.

[0041] Example 1

[0042] 1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0043] 5wt.% silica sol with a particle size of 15nm;

[0044] 12.5wt.% silica sol with a particle size of 80nm;

[0045] Silica sol with a particle size of 130 nm 2.5wt.%;

[0046] Dispersant sodium hexametaphosphate 0.5wt.%;

[0047] Oxidant sodium metavanadate 5wt.%;

[0048] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0049] pH adjuster nitric acid in appropriate amount;

[0050] Deionized water, make up to 100wt.%.

[0051] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0052] S1. Under mechanical stirring, 5 wt.% of silica sol with a particle size of 15 nm, 12.5 wt.% of silica sol with a particle size of 80 nm, and 2.5 wt.% of silica sol with a particle size of 130 nm are respectively selected and mixed evenly to obtain an abrasive;

[0053] S2. Add 0.5wt.% dispersant sodium hexametaphosphate, 5wt.% oxidant sodium metavanadate, 5wt.% auxiliary oxidant (30% hydrogen peroxide solution) and deionized water to the obtained abrasive in sequence, mix well, add a few drops of nitric acid to adjust the pH value of the polishing liquid to 6.0-7.0, and obtain a silicon carbide polishing liquid with an average particle size of 100nm.

[0054] Example 2

[0055] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0056] Silica sol with a particle size of 15 nm 0.5wt.%;

[0057] 15wt.% silica sol with a particle size of 80nm;

[0058] 4.5wt.% silica sol with a particle size of 130nm;

[0059] Dispersant sodium hexametaphosphate 0.5wt.%;

[0060] Oxidant sodium metavanadate 5wt.%;

[0061] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0062] pH adjuster nitric acid in appropriate amount;

[0063] Deionized water, make up to 100wt.%.

[0064] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0065] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0066] Figure 1The SEM image of the silicon carbide polishing liquid containing composite silica sol abrasive prepared in this embodiment is shown in FIG. Figure 1 It can be seen that due to the different van der Waals forces and electrostatic repulsions generated between silica sols of different particle sizes, some silica sols agglomerated to form linear, chain-shaped particles and irregular non-spherical particles.

[0067] Example 3

[0068] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0069] 1.5wt.% silica sol with a particle size of 15nm;

[0070] 6wt.% silica sol with a particle size of 80nm;

[0071] 12.5wt.% silica sol with a particle size of 130nm;

[0072] Dispersant sodium hexametaphosphate 0.5wt.%;

[0073] Oxidant sodium metavanadate 5wt.%;

[0074] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0075] pH adjuster nitric acid in appropriate amount;

[0076] Deionized water, make up to 100wt.%.

[0077] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0078] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0079] Example 4

[0080] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0081] 17.5wt.% silica sol with a particle size of 80nm;

[0082] Silica sol with a particle size of 130 nm 2.5wt.%;

[0083] Dispersant sodium hexametaphosphate 0.1wt.%;

[0084] Oxidant sodium metavanadate 5wt.%;

[0085] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0086] pH adjuster nitric acid in appropriate amount;

[0087] Deionized water, make up to 100wt.%.

[0088] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0089] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0090] Example 5

[0091] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0092] 15.5wt.% silica sol with a particle size of 80nm;

[0093] 4.5wt.% silica sol with a particle size of 130nm;

[0094] Dispersant sodium hexametaphosphate 0.1wt.%;

[0095] Oxidant sodium metavanadate 5wt.%;

[0096] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0097] pH adjuster nitric acid in appropriate amount;

[0098] Deionized water, make up to 100wt.%.

[0099] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0100] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0101] Example 6

[0102] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0103] 6wt.% silica sol with a particle size of 80nm;

[0104] 14wt.% silica sol with a particle size of 130nm;

[0105] Dispersant sodium hexametaphosphate 0.1wt.%;

[0106] Oxidant sodium metavanadate 5wt.%;

[0107] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0108] pH adjuster nitric acid in appropriate amount;

[0109] Deionized water, make up to 100wt.%.

[0110] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0111] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0112] Example 7

[0113] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0114] Silica sol with a particle size of 15 nm 0.5wt.%;

[0115] 15wt.% silica sol with a particle size of 80nm;

[0116] 4.5wt.% silica sol with a particle size of 130nm;

[0117] Dispersant sodium hexametaphosphate 0.1wt.%;

[0118] Oxidant sodium metavanadate 5wt.%;

[0119] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0120] pH adjuster nitric acid in appropriate amount;

[0121] Deionized water, make up to 100wt.%.

[0122] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0123] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0124] Example 8

[0125] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0126] Silica sol with a particle size of 15 nm 0.5wt.%;

[0127] 15wt.% silica sol with a particle size of 80nm;

[0128] 4.5wt.% silica sol with a particle size of 130nm;

[0129] Dispersant sodium hexametaphosphate 0.8wt.%;

[0130] Oxidant sodium metavanadate 5wt.%;

[0131] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0132] pH adjuster nitric acid in appropriate amount;

[0133] Deionized water, make up to 100wt.%.

[0134] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0135] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0136] Example 9

[0137] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0138] 1.5wt.% silica sol with a particle size of 15nm;

[0139] 6wt.% silica sol with a particle size of 80nm;

[0140] 12.5wt.% silica sol with a particle size of 130nm;

[0141] Dispersant sodium hexametaphosphate 0.1wt.%;

[0142] Oxidant sodium metavanadate 5wt.%;

[0143] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0144] pH adjuster nitric acid in appropriate amount;

[0145] Deionized water, make up to 100wt.%.

[0146] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0147] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0148] Example 10

[0149] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0150] 1.5wt.% silica sol with a particle size of 15nm;

[0151] 6wt.% silica sol with a particle size of 80nm;

[0152] 12.5wt.% silica sol with a particle size of 130nm;

[0153] Dispersant sodium hexametaphosphate 0.8wt.%;

[0154] Oxidant sodium metavanadate 5wt.%;

[0155] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0156] pH adjuster nitric acid in appropriate amount;

[0157] Deionized water, make up to 100wt.%.

[0158] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0159] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0160] Embodiment 11

[0161] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0162] 15.5wt.% silica sol with a particle size of 80nm;

[0163] 4.5wt.% silica sol with a particle size of 130nm;

[0164] Dispersant sodium hexametaphosphate 0.5wt.%;

[0165] Oxidant sodium metavanadate 5wt.%;

[0166] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0167] pH adjuster nitric acid in appropriate amount;

[0168] Deionized water, make up to 100wt.%.

[0169] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0170] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0171] Example 12

[0172] (1) The raw material composition of the silicon carbide polishing liquid containing composite silica sol abrasive is as follows:

[0173] 6wt.% silica sol with a particle size of 80nm;

[0174] 14wt.% silica sol with a particle size of 130nm;

[0175] Dispersant sodium hexametaphosphate 0.5wt.%;

[0176] Oxidant sodium metavanadate 5wt.%;

[0177] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0178] pH adjuster nitric acid in appropriate amount;

[0179] Deionized water, make up to 100wt.%.

[0180] (2) Preparation of silicon carbide polishing liquid containing composite silica sol abrasive

[0181] The preparation method of the silicon carbide polishing liquid containing the composite silica sol abrasive is the same as that in Example 1.

[0182] Comparative Example 1

[0183] (1) This comparative example is a silicon carbide polishing liquid with a silica sol abrasive having a particle size of 15 nm, and the composition is as follows:

[0184] Silica sol with a particle size of 15 nm 20wt.%;

[0185] Dispersant sodium hexametaphosphate 0.1wt.%;

[0186] Oxidant sodium metavanadate 5wt.%;

[0187] The auxiliary oxidant is hydrogen peroxide (30% hydrogen peroxide solution) 5wt.%;

[0188] pH adjuster nitric acid in appropriate amount;

[0189] Deionized water, make up to 100wt.%.

[0190] (2) The preparation method is as follows:

[0191] Under mechanical stirring, 20wt.% of silica sol with a particle size of 15nm, 0.1wt.% of dispersant sodium hexametaphosphate, 5wt.% of oxidant sodium metavanadate, 5wt.% of auxiliary oxidant (30% hydrogen peroxide solution) and deionized water are added in sequence. After mixing evenly, a few drops of nitric acid are added to adjust the pH value of the polishing liquid to 6.0-7.0 to obtain a silicon carbide fine polishing liquid with a particle size of 15nm.

[0192] Comparative Example 2

[0193] Except that the silica sol is a single silica sol with a particle size of 80 nm, the rest is the same as Comparative Example 1.

[0194] Comparative Example 3

[0195] The same procedures as those in Comparative Example 1 are followed except that the silica sol is a single silica sol with a particle size of 90 nm.

[0196] Comparative Example 4

[0197] Except that the silica sol is a single silica sol with a particle size of 100 nm, the rest is the same as Comparative Example 1.

[0198] Comparative Example 5

[0199] The same procedures as those in Comparative Example 1 are followed except that the silica sol is a single silica sol with a particle size of 130 nm.

[0200] Comparative Example 6

[0201] Except that the mass fraction of the dispersant sodium hexametaphosphate is 0.005 wt.%, the rest is the same as Example 2.

[0202] Comparative Example 7

[0203] Except that the mass fraction of the dispersant sodium hexametaphosphate is 0.005 wt.%, the rest is the same as Example 3.

[0204] Comparative Example 8

[0205] Except that the mass fraction of the dispersant sodium hexametaphosphate is 0.005 wt.%, the rest is the same as Example 5.

[0206] Comparative Example 9

[0207] Except that the mass fraction of the dispersant sodium hexametaphosphate is 0.005 wt.%, the rest is the same as Example 6.

[0208] (I) Performance Comparison of Silicon Carbide Polishing Liquids Using Composite Silica Sol Abrasives and Silica Sol Abrasives Using Single Particle Size The components of the silicon carbide polishing liquids prepared in Examples 1 to 6 and Comparative Examples 1 to 5 are shown in Table 1 below.

[0209] Table 1

[0210]

[0211] The silicon carbide polishing liquids prepared in Examples 1 to 6 and Comparative Examples 1 to 5 were tested for the material interface friction coefficient:

[0212] The microcomputer-controlled vertical friction and wear tester is manufactured by Jinan Yisite Testing Instrument Equipment Co., Ltd. SiC is used as the friction object, the polishing pad with a Shore hardness of 50A is used as the friction substrate, and the polishing liquid is used as the friction medium. The tester can automatically collect and record data such as friction coefficient and friction force during the test. During the test, the surface of the silicon carbide wafer is in contact with one side of the polishing pad, and the polishing liquid is poured into the test sample pool. During the test, the silicon carbide wafer and the polishing pad are kept rotating horizontally and completely immersed in the polishing liquid sample pool. The rotation speed of the silicon carbide wafer is 60rpm, the pressure is 80N, and the test time is 10min. After each test, the silicon carbide wafer and the polishing pad are ultrasonically cleaned in deionized water for 10 minutes to clean the polishing liquid remaining on the surface.

[0213] The specific test process parameters are shown in Table 2 below:

[0214] Table 2

[0215] Friction object: 4-inch silicon carbide wafer Friction surface: (0001)-Si surface Patching method: solid wax Friction substrate: polishing pad Medium: polishing liquid Time: 10 minutes Pressure: 80N Speed: 60rpm

[0216] The interface friction force and friction coefficient data between the polishing liquid and silicon carbide are shown in Table 3 below:

[0217] Table 3

[0218]

[0219]

[0220] The material removal rate of the silicon carbide polishing liquid prepared in Examples 1 to 6 and Comparative Examples 1 to 5 was tested: the material removal rate of the silicon carbide wafer was calculated using the weighing method, and the polishing pad material used had a Shore hardness of 50A and a compression rate of 10%. During the test, the polishing liquid was always in a mechanical stirring state to ensure uniform dispersion of the abrasive and uniform flow of the polishing liquid.

[0221] The specific polishing process parameters are shown in Table 4 below:

[0222] Table 4

[0223]

[0224] The removal rate and surface roughness data of silicon carbide polishing liquid are shown in Table 5 below:

[0225] Table 5

[0226]

[0227]

[0228] Based on the data of the above examples 1 to 6 and comparative examples 1 to 5, it can be seen that the present invention prepares a silicon carbide polishing liquid containing a composite silica sol abrasive, and enhances the friction effect of polishing at a specific ratio by mixing silica sols of different particle sizes, and synergistically adds a specific content of dispersant to control the slight agglomeration degree of the abrasive under the composite particle size, forming irregular linear and chain-shaped silica sols, and adjusting the pH range of the polishing liquid. The above characteristics play a synergistic role, and the polishing liquid significantly improves the friction coefficient at the silicon carbide interface. The polishing liquid with composite particle size silica sol in Examples 1-6 has a larger interface friction force and friction coefficient. Compared with the silicon carbide polishing liquid with a single particle size (Comparative Examples 1-5), the removal rate of the silicon surface is higher, and the surface roughness is lower and smoother. The removal efficiency of Example 2 is the best, and the removal rate on the silicon surface can reach 230nm / h. At the same time, the surface roughness after polishing can be reduced to 0.06nm, which proves that the processing efficiency of the silicon carbide polishing liquid with a composite particle size is higher, and the performance is better, with both polishing rate and high surface quality.

[0229] (II) Effect of mass percentage of dispersant on the performance of silicon carbide polishing liquid

[0230] The removal rate test method of the silicon carbide polishing liquid prepared in Examples 2, 3, 5 to 12 and Comparative Examples 6 to 9 is the same as above, and the test results are shown in Table 6 below:

[0231] Table 6

[0232]

[0233]

[0234] As shown in Table 6, Examples 1 to 3 are three types of silicon carbide polishing liquids with composite particle sizes. When 0.5% sodium hexametaphosphate is added, no gel or foaming occurs, and the silicon surface removal rate is the best. Examples 7 and 9 are three types of silicon carbide polishing liquids with composite particle sizes. When 0.1% sodium hexametaphosphate is added, slight foaming is found during the preparation process, and the silicon surface removal rate is not as good as that of Examples 2 and 3. It may be that the insufficient amount of sodium hexametaphosphate added causes the composite abrasive to agglomerate and gel, affecting the polishing efficiency; Examples 8 and 10 are three types of silicon carbide polishing liquids with composite particle sizes. When 0.8% sodium hexametaphosphate is added, no gel or foaming occurs during the preparation process, but the silicon surface removal rate is not as good as that of Examples 2 and 3. It is speculated that the excessive amount of sodium hexametaphosphate added may cause the free sodium hexametaphosphate to form micelles, reducing the polishing removal rate. Examples 4 to 6 are two types of silicon carbide polishing liquids with composite particle sizes. When 0.1% sodium hexametaphosphate is added, the dispersion effect is the best, and the silicon surface removal rate is good. Example 11 Example 12 is a silicon carbide polishing liquid with two composite particle sizes. 0.5% sodium hexametaphosphate is added. No gel or foaming occurs, but the silicon surface removal rate is not as good as that of Example 5 and Example 6. It is speculated that the excessive addition may cause the free sodium hexametaphosphate to form micelles, reducing the polishing removal rate. Comparative Examples 6 to 9 add 0.005% sodium hexametaphosphate, and gelation occurs during the preparation process, indicating that the amount of sodium hexametaphosphate added is too little, and the dispersion effect of the polishing liquid is poor. In summary, the particle size ratio of the composite silica sol is interrelated with the amount of dispersant used, and a specific amount of dispersant is required to ensure the dispersion effect of the polishing liquid and the silicon surface removal rate.

[0235] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A silicon carbide polishing liquid containing a composite silica sol abrasive, characterized in that: The invention comprises the following components by mass percentage: 1%-20% of composite silica sol abrasive, 0.01%-1% of dispersant, 0.1%-10% of oxidant, 1%-20% of auxiliary oxidant, 0.001%-0.1% of pH regulator, and the rest is deionized water; the composite silica sol abrasive comprises at least two silica sols with a particle size difference of more than 50nm.

2. The silicon carbide polishing liquid containing composite silica sol abrasive according to claim 1, characterized in that: The particle size of the silica sol is 15-130 nm; and / or the pH of the silicon carbide polishing liquid is 6.0-7.

0.

3. The silicon carbide polishing liquid containing composite silica sol abrasive according to claim 2, characterized in that: Based on the total mass of the composite silica sol abrasive, the composite silica sol abrasive consists of 30%-88% of silica sol with a particle size of 80nm and 12%-70% of silica sol with a particle size of 130nm; the mass proportion of the dispersant in the silicon carbide polishing liquid is 0.1%.

4. The silicon carbide polishing liquid containing composite silica sol abrasive according to claim 2, characterized in that: Based on the total mass of the composite silica sol abrasive, the composite silica sol abrasive consists of 2%-25% of silica sol with a particle size of 15 nm, 30%-75% of silica sol with a particle size of 80 nm and 12%-63% of silica sol with a particle size of 130 nm; the mass proportion of the dispersant in the silicon carbide polishing liquid is 0.5%.

5. The silicon carbide polishing liquid containing composite silica sol abrasive according to claim 1, characterized in that: Includes one or more of the following characteristics: (1) The silica sol is spherical silica sol; (2) The dispersant is selected from any one or more of sodium hexametaphosphate, sodium tripolyphosphate, and sodium polyacrylate; (3) The oxidant is selected from any one or more of sodium metavanadate, sodium orthovanadate, potassium metavanadate, potassium orthovanadate, ammonium metavanadate, potassium molybdate, sodium molybdate, and ammonium molybdate; (4) The auxiliary oxidant is selected from any one or more of hydrogen peroxide, potassium permanganate, potassium manganate, potassium ferrate, sodium periodate, iodic acid, and potassium iodate; (5) The pH adjuster is selected from any one or more of nitric acid, sulfuric acid, citric acid, malic acid, tartaric acid, oxalic acid, acetic acid, potassium hydroxide, sodium hydroxide, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate.

6. The silicon carbide polishing liquid containing composite silica sol abrasive according to claim 2, characterized in that: Includes one or more of the following characteristics: 1a) The silica sol is prepared by an ion exchange method, a sol-gel method or a sodium silicate hydrolysis method; 2a) the dispersant is selected from sodium hexametaphosphate; 3a) the oxidant is selected from sodium metavanadate; 4a) The auxiliary oxidant is selected from hydrogen peroxide.

7. A method for preparing a silicon carbide polishing liquid containing a composite silica sol abrasive according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Evenly mix silica sols of different particle sizes to obtain composite silica sol abrasive; Step 2: Add dispersant, oxidant, auxiliary oxidant and deionized water to the composite silica sol abrasive in sequence, mix well, add pH adjuster to adjust the pH to 6.0-7.0, and obtain silicon carbide polishing liquid.

8. The method for preparing a silicon carbide polishing liquid containing a composite silica sol abrasive according to claim 7, characterized in that: The uniform mixing is achieved by mechanical stirring.

9. Use of the silicon carbide polishing liquid containing the composite silica sol abrasive according to any one of claims 1 to 6 or the silicon carbide polishing liquid containing the composite silica sol abrasive prepared by the preparation method according to claim 7 or 8 in chemical mechanical polishing.

10. The use according to claim 9, characterized in that Suitable for silicon carbide wafer polishing.

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