A chemical mechanical polishing liquid and its preparation method and application

Abstract

The present invention provides a chemical mechanical polishing liquid, a preparation method and an application thereof. Different from a common alkaline lithium tantalate polishing liquid, the pH value of the chemical mechanical polishing liquid provided by the present invention is 1-6. By adding a single organic acid or a fluoride ion salt as a polishing accelerator in an acidic pH environment, the present invention can significantly improve the polishing rate of a lithium tantalate wafer; by simultaneously adding an organic acid and a fluoride ion salt to the polishing liquid, the two have a significant synergistic effect in an acidic environment, and can further improve the removal rate of the lithium tantalate wafer (the rate improvement reaches 168.43%, and the lithium tantalate removal rate is as high as 4923Å / min), and the effect of improving the removal rate is significantly higher than that of adding an organic acid or a fluoride ion salt alone.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium tantalate wafer polishing, and in particular relates to a chemical mechanical polishing liquid and a preparation method and application thereof. Background Art

[0002] Lithium tantalate crystal (LiTaO 3 ) is a typical multifunctional single crystal material with excellent piezoelectric, electro-optical and thermoelectric properties such as large electromechanical coupling coefficient, low loss, high temperature stability and good high frequency performance. At present, lithium tantalate wafers are mainly used in satellite reception, piezoelectric sensing, aerospace, infrared guidance, mobile communications and display. They can be used as high-frequency and medium-frequency bandwidth, low insertion loss, high frequency stability and miniaturization of surface acoustic wave and bulk wave devices, such as surface wave filters, resonators, etc. In addition, with the rapid development of the electronic information industry, lithium tantalate crystals have also become an indispensable material in piezoelectric, acousto-optic, laser and other devices.

[0003] However, high-performance electronic components require that the lattice of lithium tantalate wafers be complete, with high flatness and an undamaged wafer surface. Even if there are tiny defects on the polished surface of lithium tantalate wafers, it will cause changes in the lattice structure, affecting the frequency accuracy, frequency stability and loss of the components. In addition, since lithium tantalate crystals are typical hard and brittle materials with mechanical properties such as cleavage and anisotropy, it is difficult to obtain a high flatness and undamaged wafer surface using traditional grinding and polishing. Chemical mechanical polishing (CMP), as a technology that can achieve global flattening, is widely used to process lithium tantalate wafers. Among them, polishing liquid, as an important consumable in the CMP process, will directly affect the removal rate and surface quality of the wafer. Therefore, studying and improving lithium tantalate polishing liquid is of great practical significance for the polishing of lithium tantalate wafers.

[0004] At present, due to the limitation of high flatness (surface roughness Sa<0.5nm) required for lithium tantalate wafers, the removal rate is difficult to increase during precision polishing, resulting in a long polishing time. Patent CN117247737A proposes a lithium tantalate polishing liquid. By adding a non-ionic surfactant and isopropanol to the polishing liquid, the removal rate of lithium tantalate can reach 2000 Å / min when the surface roughness is less than 0.3 nm. Patent CN114085616A proposes a lithium tantalate polishing liquid. By adding an inorganic salt or organic salt containing a monovalent cation, the removal rate of lithium tantalate can reach 1500 Å / min when the surface roughness is less than 0.6nm. Patent CN109988509B proposes a lithium tantalate polishing liquid. By adding potassium fluoride and sodium sulfate as nucleophilic reagents and adding an oxidant at the same time, the removal rate of lithium tantalate can finally reach 1500 Å / min. However, the above-mentioned lithium tantalate polishing liquid still has the problem of low removal rate while ensuring high flatness of the wafer surface. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a chemical mechanical polishing liquid and a preparation method and application thereof. The chemical mechanical polishing liquid can further improve the removal rate of lithium tantalate wafers while ensuring high flatness of the wafer surface.

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

[0007] In a first aspect, the present invention provides a chemical mechanical polishing liquid, comprising: abrasive particles, a polishing accelerator, a pH regulator and water;

[0008] The polishing accelerator is a fluoride ion salt, or an organic acid and a fluoride ion salt;

[0009] The pH value of the chemical mechanical polishing liquid is 1-6.

[0010] Preferably, the abrasive particles are one or more of silicon dioxide, aluminum oxide, cerium oxide, zirconium oxide, titanium oxide or iron oxide.

[0011] Preferably, the particle size of the abrasive particles is 30-200 nm.

[0012] Preferably, the organic acid is selected from one or both of organic carboxylic acids and sulfonic acids.

[0013] Preferably, the fluoride ion salt is MF n , wherein the M is Li + 、Na + , K + , Ca 2+ Mg2+ or NH 4 + Any one of , n is 1 or 2.

[0014] Preferably, the pH regulator is selected from one or both of an acid regulator and an alkali regulator.

[0015] Preferably, the pH of the chemical mechanical polishing solution is 3-5.

[0016] Preferably, the abrasive particles are one or both of fumed silica and sol silica.

[0017] Preferably, the particle size of the abrasive particles is 70-150 nm.

[0018] Preferably, the organic acid is selected from one or both of saturated fatty carboxylic acids and aromatic carboxylic acids.

[0019] Preferably, the fluoride ion salt is one or both of sodium fluoride and potassium fluoride.

[0020] Preferably, the pH regulator is an acid regulator, and the acid regulator is selected from inorganic acids, and the inorganic acid is one or more of nitric acid, sulfuric acid, hydrochloric acid or phosphoric acid.

[0021] Preferably, the pH regulator is an alkali regulator, and the alkali regulator is selected from an inorganic base or an organic base, the inorganic base is one or more of potassium hydroxide, sodium hydroxide or ammonium hydroxide, and the organic base is one or more of ethanolamine, ethylenediamine and diethylamine.

[0022] Preferably, the organic acid is selected from one or more of tartaric acid, citric acid, acetic acid, oxalic acid, lactic acid, propionic acid, malonic acid, butyric acid, succinic acid, valeric acid, glutaric acid, L-malic acid, glycine, alanine, glutamic acid, benzoic acid, phthalic acid, methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid.

[0023] Preferably, the mass percentage of the abrasive particles in the chemical mechanical polishing solution is 5-50 wt %.

[0024] Preferably, the mass percentage of the organic acid in the chemical mechanical polishing solution is 0.01-10 wt %.

[0025] Preferably, the mass percentage of the fluoride ion salt in the chemical mechanical polishing solution is 0.01-10 wt %.

[0026] Preferably, in terms of mass percentage, the mass percentage of the abrasive particles in the chemical mechanical polishing solution is 20-35 wt %.

[0027] Preferably, the mass percentage of the organic acid in the chemical mechanical polishing solution is 0.5-5 wt %.

[0028] Preferably, the mass percentage of the fluoride ion salt in the chemical mechanical polishing solution is 0.1-3 wt %.

[0029] Preferably, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, potassium fluoride, water and a pH adjuster;

[0030] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, sodium fluoride, water and a pH adjuster;

[0031] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, citric acid, potassium fluoride, water and a pH adjuster;

[0032] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, citric acid, sodium fluoride, water and a pH adjuster;

[0033] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, tartaric acid, potassium fluoride, water and a pH adjuster;

[0034] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, tartaric acid, sodium fluoride, water and a pH adjuster;

[0035] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, acetic acid, sodium fluoride, water and a pH adjuster;

[0036] Or, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, acetic acid, potassium fluoride, water and a pH adjuster;

[0037] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, succinic acid, sodium fluoride, water and a pH adjuster;

[0038] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, succinic acid, potassium fluoride, water and a pH adjuster;

[0039] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, lactic acid, potassium fluoride, water and a pH adjuster;

[0040] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, oxalic acid, potassium fluoride, water and a pH adjuster;

[0041] Or, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, glycine, potassium fluoride, water and a pH adjuster;

[0042] Alternatively, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, methanesulfonic acid, sodium fluoride, water and a pH adjuster.

[0043] Preferably, the polishing liquid also includes a bactericide.

[0044] In a second aspect, the present invention provides a method for preparing the chemical mechanical polishing solution, comprising:

[0045] Mixing silicon dioxide with water to obtain agent A; mixing a polishing accelerator with water to obtain agent B;

[0046] Agent A and agent B are mixed and the pH is adjusted to obtain a chemical mechanical polishing solution.

[0047] In a third aspect, the present invention further provides a use of the chemical mechanical polishing solution in polishing wafers containing lithium tantalate or lithium niobate.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention provides a chemical mechanical polishing liquid. Different from the common alkaline lithium tantalate polishing liquid, the pH value of the chemical mechanical polishing liquid provided by the present invention is 1-6. By adding a single organic acid or fluoride ion salt as a polishing accelerator in an acidic pH environment, the polishing rate of the lithium tantalate wafer can be significantly improved (the organic carboxylic acid rate is improved by 29.12%-82.99%, and the fluoride ion salt rate is improved by 50.05%-58.56%). The present invention further adds an organic acid and a fluoride ion salt to the polishing liquid at the same time. The organic acid and the fluoride ion salt have a significant synergistic effect in an acidic environment, and the removal rate of the lithium tantalate wafer can be further improved (the rate is improved by 168.43%, and the lithium tantalate removal rate is as high as 4923 Å / min). The improvement effect of the removal rate is significantly higher than that of adding an organic acid or a fluoride ion salt alone.

[0050] In addition, the chemical mechanical polishing liquid provided by the present invention can change the removal rate of the lithium tantalate wafer by adjusting the content of the organic acid or fluoride ion salt therein, thereby achieving adjustable removal rate of the lithium tantalate wafer and better adapting to the process requirements of different processes. DETAILED DESCRIPTION

[0051] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] In view of the problem that the lithium tantalate polishing liquid in the prior art still has a low removal rate while ensuring high flatness of the wafer surface, the present invention provides a chemical mechanical polishing liquid, which includes: abrasive particles, a polishing accelerator, a pH regulator and water.

[0053] In the present invention, the abrasive particles are selected from one or more of silicon dioxide, aluminum oxide, cerium oxide, zirconium oxide, titanium oxide or iron oxide, preferably silicon dioxide. The silicon dioxide can be selected from fumed silica and / or sol silica, which is used as abrasive particles to provide abrasive mechanical force for the polishing liquid, lubricate the polishing pad and the wafer surface, and serve as a carrier for conveying a polishing accelerator. In the present invention, the particle size of the abrasive particles is 30 to 200 nm, preferably 70 to 150 nm. In the present invention, the mass percentage of the abrasive particles in the chemical mechanical polishing solution is 5 to 50 wt%, preferably 20 to 35 wt%, and most preferably 30 wt%. For example, the content of the abrasive particles is 5 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 15 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 29 wt%, 31 wt%, 32 wt%, 35 wt%, 38 wt%, 40 wt%, 41 wt%, 43 wt%, 47 wt%, 48 wt%, and 50 wt%.

[0054] It should be noted that the content of the abrasive particles is not limited to the above-mentioned point values, and other point values ​​within the numerical range are applicable. To avoid complexity, they will not be described one by one.

[0055] In the present invention, the polishing accelerator is used to increase the grinding mechanical force and chemical force of the polishing liquid and improve the removal rate of lithium tantalate. Through experimental exploration, when a single fluoride ion salt is used as a polishing accelerator, the removal rate of lithium tantalate wafers can be increased (the rate is increased by 50.05%~58.56%), while the addition of chloride ion salts and nitrates has no obvious effect on the removal rate of lithium tantalate wafers. Therefore, fluoride ion salts are preferably used as one of the components of the polishing accelerator. At the same time, when a single organic acid is used as a polishing accelerator, different organic acids can increase the removal rate of lithium tantalate (the rate is increased by 29.12%~82.99%). Therefore, the present invention preferably uses organic acids and fluoride ion salts as polishing accelerators together, and it is found that the combination of the two has an excellent synergistic effect on the removal rate of lithium tantalate wafers.

[0056] In the present invention, the mass percentage of the organic acid in the chemical mechanical polishing solution is 0.01~10 wt%, preferably 0.5~5 wt%, more preferably 1~2 wt%. For example, the content of the organic acid is 0.01 wt%, 0.5 wt%, 1wt%, 1.5 wt%, 2 wt%, 3 wt%, 3.5 wt%, 5 wt%, 6 wt%, 7 wt%, 9 wt% or 10 wt%.

[0057] It should be noted that the mass percentage of the organic acid in the chemical mechanical polishing liquid is not limited to the above-mentioned point values, and other point values ​​within the numerical range are applicable. To avoid complexity, they will not be described one by one.

[0058] In the present invention, the organic acid is selected from organic carboxylic acid and / or sulfonic acid; preferably, the organic acid is selected from saturated fatty carboxylic acid and / or aromatic carboxylic acid. Preferably, the organic acid is R-COOH, wherein R is selected from substituted or unsubstituted C1~C6 alkyl; the substituted group in the "substituted or unsubstituted" is selected from any one of hydroxyl, amino or carboxyl. In some embodiments of the present invention, the organic acid is preferably selected from any one or more of tartaric acid, citric acid, acetic acid, oxalic acid, lactic acid, propionic acid, malonic acid, butyric acid, succinic acid, valeric acid, glutaric acid, L-malic acid, glycine, alanine, glutamic acid, benzoic acid, phthalic acid, methanesulfonic acid, benzenesulfonic acid or p-toluenesulfonic acid. Since different organic acids have obvious differences in the degree of improvement of the removal rate of lithium tantalate wafers, it is more preferably any one or more of tartaric acid, acetic acid or succinic acid.

[0059] In the present invention, the chemical formula of the fluoride ion salt can be expressed as MF n , wherein the M is Li + 、Na + , K + , Ca 2+ Mg 2+ or NH 4 + Any one of, n is 1 or 2. In the present invention, the fluoride ion salt is preferably sodium fluoride and / or potassium fluoride. In the present invention, the mass percentage of the fluoride ion salt in the chemical mechanical polishing liquid is 0.01~10 wt%, preferably 0.5~5wt%, more preferably 1~2 wt%, and for example, the content of the fluoride ion salt is 0.01 wt%, 0.5 wt%, 1 wt%, 1.5wt%, 2 wt%, 3 wt%, 3.5 wt%, 5 wt%, 6 wt%, 7 wt%, 9 wt% or 10 wt%. In some embodiments of the present invention, the mass ratio of the organic acid to the fluoride ion salt is (0.1~2):1, preferably (0.33~2):1, and more preferably 1:1.

[0060] It should be noted that the mass percentage of the fluoride ion salt in the chemical mechanical polishing liquid is not limited to the above-mentioned point values, and other point values ​​within the numerical range are applicable. To avoid complexity, they will not be described one by one.

[0061] In the present invention, the pH regulator is used to adjust the pH of the chemical mechanical polishing liquid to 1-6, preferably 3-5, more preferably 3.5-4.5. For example, the pH of the polishing liquid is 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 4.8, 5, 5.5, 6. The amount and type of the pH regulator are determined according to the value of the adjusted pH. Since the pH of the system of abrasive particles and polishing accelerators may be higher or lower than the preferred range, the pH regulator is selected from one or both of an acid regulator and an alkali regulator; the alkali regulator is selected from an inorganic base or an organic base, the inorganic base is selected from any one or more of potassium hydroxide, sodium hydroxide or ammonium hydroxide, and the organic base is selected from any one or more of ethanolamine, ethylenediamine or diethylamine; the acid regulator is an inorganic acid, and the inorganic acid is selected from any one or more of nitric acid, sulfuric acid, hydrochloric acid or phosphoric acid.

[0062] It should be noted that the pH of the polishing liquid is not limited to the above-mentioned values, and other values ​​within the numerical range are applicable. To avoid complexity, they will not be described one by one.

[0063] In some preferred embodiments of the present invention, the polishing liquid further comprises a fungicide, specifically, the fungicide is selected from MTSB330 fungicide or KORDEK fungicide. The present invention has no particular limitation on the source of the fungicide, and it can be a common commercial product known to those skilled in the art.

[0064] In some preferred embodiments of the present invention, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, potassium fluoride, water and a pH adjuster;

[0065] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, sodium fluoride, water and a pH adjuster;

[0066] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, citric acid, potassium fluoride, water and a pH adjuster;

[0067] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, citric acid, sodium fluoride, water and a pH adjuster;

[0068] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, tartaric acid, potassium fluoride, water and a pH adjuster;

[0069] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, tartaric acid, sodium fluoride, water and a pH adjuster;

[0070] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, acetic acid, sodium fluoride, water and a pH adjuster;

[0071] Or, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, acetic acid, potassium fluoride, water and a pH adjuster;

[0072] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, succinic acid, sodium fluoride, water and a pH adjuster;

[0073] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, succinic acid, potassium fluoride, water and a pH adjuster;

[0074] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, lactic acid, potassium fluoride, water and a pH adjuster;

[0075] Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, oxalic acid, potassium fluoride, water and a pH adjuster;

[0076] Or, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, glycine, potassium fluoride, water and a pH adjuster;

[0077] Alternatively, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, methanesulfonic acid, sodium fluoride, water and a pH adjuster.

[0078] In some specific embodiments of the present invention, the chemical mechanical polishing solution includes abrasive particles, an organic acid, a fluoride ion salt, water and a pH regulator, and the content of each component is based on the total mass of all components. The content of water is 30-90wt%, preferably 50-~70wt%. The chemical mechanical polishing solution specifically includes:

[0079] SiO with a particle size of 100 nm 2 30 wt%, citric acid 0.33 wt%, potassium fluoride 1 wt%, pH 3.5;

[0080] SiO with a particle size of 100 nm 2 30 wt%, citric acid 1 wt%, potassium fluoride 1 wt%, pH 3.5;

[0081] SiO with a particle size of 100 nm 2 30 wt%, citric acid 2 wt%, potassium fluoride 1 wt%, pH 3.5;

[0082] SiO with a particle size of 100 nm 230 wt%, tartaric acid 0.33 wt%, potassium fluoride 1 wt%, pH 3.5;

[0083] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 1 wt%, potassium fluoride 1 wt%, pH 3.5;

[0084] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 2 wt%, potassium fluoride 1 wt%, pH 3.5;

[0085] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 0.33 wt%, sodium fluoride 1 wt%, pH 3.5;

[0086] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 1 wt%, sodium fluoride 1 wt%, pH 3.5;

[0087] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 2 wt%, sodium fluoride 1 wt%, pH 3.5;

[0088] SiO with a particle size of 100 nm 2 30 wt%, lactic acid 1 wt%, potassium fluoride 1 wt%, pH 3.5;

[0089] SiO with a particle size of 100 nm 2 30 wt%, oxalic acid 1 wt%, potassium fluoride 1 wt%, pH 3.5;

[0090] SiO with a particle size of 100 nm 2 30 wt%, glycine 1 wt%, potassium fluoride 1 wt%, pH 3.5;

[0091] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 1 wt%, potassium fluoride 0.33 wt%, pH 3.5;

[0092] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 1 wt%, potassium fluoride 2 wt%, pH 3.5;

[0093] SiO with a particle size of 100 nm 2 30 wt%, citric acid 1 wt%, sodium fluoride 0.33 wt%, pH 3.5;

[0094] SiO with a particle size of 100 nm2 30 wt%, citric acid 1 wt%, sodium fluoride 1 wt%, pH 3.5;

[0095] SiO with a particle size of 100 nm 2 30 wt%, citric acid 1 wt%, sodium fluoride 2 wt%, pH 3.5;

[0096] SiO with a particle size of 100 nm 2 30 wt%, acetic acid 0.33 wt%, sodium fluoride 1 wt%, pH 3.5;

[0097] SiO with a particle size of 100 nm 2 30 wt%, acetic acid 1 wt%, sodium fluoride 1 wt%, pH 3.5;

[0098] SiO with a particle size of 100 nm 2 30 wt%, acetic acid 2 wt%, sodium fluoride 1 wt%, pH 3.5;

[0099] SiO with a particle size of 100 nm 2 30 wt%, succinic acid 0.33 wt%, sodium fluoride 1 wt%, pH 3.5;

[0100] SiO with a particle size of 100 nm 2 30 wt%, succinic acid 1 wt%, sodium fluoride 1 wt%, pH 3.5;

[0101] SiO with a particle size of 100 nm 2 30 wt%, succinic acid 2 wt%, sodium fluoride 1 wt%, pH 3.5;

[0102] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 1 wt%, potassium fluoride 1 wt%, pH 6.0;

[0103] SiO with a particle size of 100 nm 2 30 wt%, tartaric acid 1 wt%, potassium fluoride 1 wt%, pH 4.5;

[0104] SiO with a particle size of 100 nm 2 30 wt%, methanesulfonic acid 1 wt%, sodium fluoride 1 wt%, pH 3.5;

[0105] SiO with a particle size of 100 nm 2 30 wt%, potassium fluoride 2 wt%, pH 3.5;

[0106] SiO with a particle size of 100 nm 230 wt%, sodium fluoride 2 wt%, pH 3.5.

[0107] The present invention also provides a method for preparing the chemical mechanical polishing solution, which comprises:

[0108] Silicon oxide, a polishing accelerator, a pH adjuster and water are mixed, and the pH is adjusted to 1-6 to obtain a chemical mechanical polishing solution.

[0109] To ensure that silicon oxide is fully dissolved, in some embodiments of the present invention, the preparation method preferably includes:

[0110] Mixing silicon dioxide with water to obtain agent A; mixing a polishing accelerator with water to obtain agent B;

[0111] After mixing agent A, agent B and a pH adjuster, the pH is adjusted to 1-6 to obtain a chemical mechanical polishing solution.

[0112] In the present invention, the "mixing" mentioned above is carried out under stirring conditions. The mixing time of the agent A, agent B and pH adjuster is 5 to 30 minutes, preferably 10 to 20 minutes.

[0113] The preparation method provided by the present invention is simple, convenient, easy to operate, and is conducive to large-scale production or industrial production.

[0114] The present invention also provides an application of the chemical mechanical polishing liquid in polishing a wafer containing lithium tantalate or lithium niobate.

[0115] The present invention takes lithium tantalate wafer as an example, uses a 4-inch lithium tantalate wafer, a Buehler Ecomet-30 desktop polisher, a grinding pressure of 6 psi, a SUBA800 polishing pad, a grinding table speed of 150 rpm, a grinding head speed of 130 rpm, and a polishing liquid dripping speed of 200 mL / min. Finally, the lithium tantalate removal rate and surface roughness are tested.

[0116] The results showed that when the surface roughness was less than 0.5 nm, the lithium tantalate removal rate was significantly improved, reaching a maximum of 4923 Å / min.

[0117] In summary, the chemical mechanical polishing solution provided by the present invention solves the problem that the lithium tantalate polishing solution in the prior art has a low removal rate while ensuring high flatness of the wafer surface.

[0118] In order to further illustrate the present invention, the following examples are provided for detailed description. The experimental raw materials used in the following examples of the present invention are all common commercially available products.

[0119] Embodiments 1 to 28

[0120] The formula of the chemical mechanical polishing solution involved in Examples 1 to 28 is shown in Table 1:

[0121] Table 1

[0122]

[0123] The specific preparation method is as follows:

[0124] Taking Example 1 as an example, the slurry containing abrasive particles is mixed with water to prepare Agent A with a solid content of 45wt%, and the polishing accelerator is mixed with water at a content of 3 times (the citric acid content in Example 1 is 0.33%, then 1wt% citric acid is added to mix with water; the KF content is 1%, then 3wt% KF is added to mix with water) to prepare Agent B. During polishing, Agent A and Agent B are mixed at a mass ratio of 2:1, and after stirring for 10 minutes, nitric acid is added as a pH adjuster to adjust to the required pH value for standby use.

[0125] Comparative Examples 1 to 14

[0126] The formulas of the chemical mechanical polishing solutions involved in Comparative Examples 1 to 14 are shown in Table 2:

[0127] Table 2

[0128]

[0129] For the specific preparation method, refer to the above Examples 1 to 28.

[0130] Polishing effect test of lithium tantalate wafer:

[0131] Polishing conditions: a 4-inch lithium tantalate wafer was used, the polishing machine was a Buehler Ecomet-30 desktop polisher, the grinding pressure was 6 psi, the SUBA800 polishing pad, the grinding table speed was 150 rpm, the grinding head speed was 130 rpm, and the polishing liquid drop rate was 200 mL / min. The polishing liquid was the polishing liquid prepared in Examples 1 to 28 and Comparative Examples 1 to 14.

[0132] The polishing test results are shown in Table 3 below (wherein, the lithium tantalate removal rate is calculated by weighing: the mass of the lithium tantalate wafer before polishing and the mass after polishing are weighed respectively, and the calculation formula of the removal rate is (mass before polishing - mass after polishing) / (density×wafer area×polishing time); the surface roughness is measured by atomic force microscopy (AFM): the measurement range is 50×50 microns, and the surface roughness is measured at the center, middle and edge of the wafer respectively. Among them, the surface roughness in Table 3 is represented by the largest value in the center, middle and edge of the wafer):

[0133] Table 3

[0134]

[0135] Taking Comparative Example 1 as a benchmark, the removal rate improvement effect of Comparative Examples 2 to 14 and Examples 1 to 28 compared with Comparative Example 1 was calculated, and the calculation formula is as follows:

[0136] [(Comparative Example m or Example n-Comparative Example 1) / Comparative Example 1]×100%, m=2~14, n=1~28.

[0137] The calculation results are shown in Table 4 below:

[0138] Table 4

[0139]

[0140] Analyzing the data in Table 3 and Table 4, it can be seen from the comparison between Comparative Examples 1 to 5 and Examples 27 to 28 that when inorganic salts are added alone, the addition of fluoride ion salts can increase the removal rate of lithium tantalate (the rate is increased by 50.05% to 58.56%), while the addition of chloride ion salts and nitrates has no significant effect on the removal rate of lithium tantalate. It can be seen from the comparison between Comparative Examples 1 and Comparative Examples 6 to 12 that when organic acids are added alone, different organic acids can increase the removal rate of lithium tantalate (the rate is increased by 29.12% to 82.99%), but the degree of improvement of the removal rate by different organic acids is significantly different. By comparing Comparative Examples 1 to 14 with Examples 2, 5, 8, 10, 11, 12, 16, 19, 22, 26, 27, and 28, it can be seen that when 1 wt% of fluoride salt and 1 wt% of organic acid are added simultaneously, the removal rate of lithium tantalate can be further improved compared to adding 2 wt% of fluoride salt or organic acid alone, indicating that the two have a synergistic effect. Among them, the chemical mechanical polishing liquid obtained in Example 19 has a removal rate of lithium tantalate of up to 4923 Å / min, and the removal rate is increased by 168.43%.

[0141] It should be noted that the synergistic effect of fluoride salts and organic acids in the present invention can only work under acidic pH conditions. By comparing Examples 24 and 25 with Example 5, it can be seen that in the acidic chemical mechanical polishing solution, as the pH increases, the removal rate of lithium tantalate gradually decreases. By comparing Comparative Examples 13 and 14 with Example 19, it can be seen that the pH of the polishing solution changes from acidic to neutral and then to alkaline, and the removal rate of lithium tantalate gradually decreases. This may be because when the pH is acidic, the surface of the lithium tantalate wafer is positively charged. At this time, the addition of fluoride salts and organic acids can enhance the bonding of silica abrasives to the surface of lithium tantalate to improve the grinding efficiency, thereby increasing the removal rate of lithium tantalate.

[0142] In summary, the present invention adds organic acid and fluoride ion salt to the chemical mechanical polishing liquid at the same time. The two have a significant synergistic effect in an acidic environment, and can further improve the removal rate of lithium tantalate wafers. The effect of improving the removal rate is higher than adding organic acid or fluoride ion salt alone.

[0143] By comparing Comparative Examples 1, 6, Example 27 and Examples 1 to 3, it can be seen that adding different concentrations of citric acid while adding potassium fluoride can increase the removal rate of lithium tantalate, and the removal rate of lithium tantalate can be changed according to the amount of citric acid added; by comparing Comparative Examples 1, 7, Example 27 and Examples 4 to 6, adding different concentrations of tartaric acid while adding potassium fluoride can increase the removal rate of lithium tantalate, and the removal rate of lithium tantalate can be changed according to the amount of tartaric acid added; by comparing Comparative Examples 1, 7, Example 28 and Examples 7 to 9, it can be seen that adding different concentrations of tartaric acid while adding sodium fluoride can increase the removal rate of lithium tantalate, and the removal rate of lithium tantalate can be changed according to the amount of tartaric acid added; by comparing Comparative Examples 1, 7, Example 27 and Examples 5, 13, and 14, it can be seen that adding different concentrations of tartaric acid while adding tartaric acid can increase the removal rate of lithium tantalate, and the removal rate of lithium tantalate can be changed according to the amount of tartaric acid added. According to the comparative examples 1, 6, Example 28 and Examples 15 to 17, adding different concentrations of sodium fluoride while adding citric acid can improve the removal rate of lithium tantalate, and the removal rate of lithium tantalate can be changed according to the addition amount of sodium fluoride; According to the comparative examples 1, 11, Example 28 and Examples 18 to 20, adding different concentrations of acetic acid while adding sodium fluoride can improve the removal rate of lithium tantalate, and the removal rate of lithium tantalate can be changed according to the addition amount of acetic acid; According to the comparative examples 1, 12, Example 28 and Examples 21 to 23, adding different concentrations of succinic acid while adding sodium fluoride can improve the removal rate of lithium tantalate, and the removal rate of lithium tantalate can be changed according to the addition amount of succinic acid.

[0144] The above results indicate that the chemical mechanical polishing solution provided by the present invention can change the removal rate by adjusting the content of organic acid or fluoride ion salt therein, thereby achieving adjustable removal rate of lithium tantalate, and can better adapt to the process requirements of different processes.

[0145] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Application of a chemical mechanical polishing liquid in polishing wafers containing lithium tantalate or lithium niobate, characterized in that: The chemical mechanical polishing liquid comprises: abrasive particles, a polishing accelerator, a pH regulator and water; The polishing accelerator is a fluoride ion salt, or an organic acid and a fluoride ion salt, and the organic acid is selected from one or two of organic carboxylic acids and sulfonic acids; The pH of the chemical mechanical polishing solution is 1-6; The abrasive particles are one or more of silicon dioxide, aluminum oxide, cerium oxide, zirconium oxide, titanium oxide or iron oxide; The particle size of the abrasive particles is 30-200 nm; The fluoride ion salt is MF n , wherein the M is Li + 、Na + , K + , Ca 2+ Mg 2+ or NH4 + Any one of, n is 1 or 2; In terms of mass percentage, the mass percentage of the abrasive particles in the chemical mechanical polishing solution is 5-50 wt %; The mass percentage of the organic acid in the chemical mechanical polishing liquid is 0.01-10 wt %; And / or, the mass percentage of the fluoride ion salt in the chemical mechanical polishing solution is 0.01-10 wt %.

2. The use according to claim 1, characterized in that: The pH regulator is selected from one or two of an acid regulator and an alkali regulator; And / or, the pH value of the chemical mechanical polishing solution is 3-5.

3. The use according to claim 1, characterized in that: The abrasive particles are one or both of fumed silica and sol silica; And / or, the particle size of the abrasive particles is 70-150 nm; And / or, the organic acid is selected from one or two of saturated fatty carboxylic acids and aromatic carboxylic acids; And / or, the fluoride ion salt is one or both of sodium fluoride and potassium fluoride; And / or, the pH regulator is an acid regulator, the acid regulator is selected from an inorganic acid, and the inorganic acid is one or more of nitric acid, sulfuric acid, hydrochloric acid or phosphoric acid; And / or, the pH regulator is an alkali regulator, the alkali regulator is selected from an inorganic base or an organic base, the inorganic base is one or more of potassium hydroxide, sodium hydroxide or ammonium hydroxide, and the organic base is one or more of ethanolamine, ethylenediamine and diethylamine.

4. The use according to claim 1, characterized in that: The organic acid is selected from one or more of tartaric acid, citric acid, acetic acid, oxalic acid, lactic acid, propionic acid, malonic acid, butyric acid, succinic acid, valeric acid, glutaric acid, L-malic acid, glycine, alanine, glutamic acid, benzoic acid, phthalic acid, methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid.

5. The use according to claim 1, characterized in that: In terms of mass percentage, the mass percentage of the abrasive particles in the chemical mechanical polishing solution is 20-35 wt %; And / or, the mass percentage of the organic acid in the chemical mechanical polishing liquid is 0.5-5 wt %; And / or, the mass percentage of the fluoride ion salt in the chemical mechanical polishing solution is 0.1-3wt%.

6. The use according to claim 1, characterized in that: The chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, potassium fluoride, water and a pH regulator; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, sodium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, citric acid, potassium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, citric acid, sodium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, tartaric acid, potassium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, tartaric acid, sodium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, acetic acid, sodium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, acetic acid, potassium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, succinic acid, sodium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, succinic acid, potassium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, lactic acid, potassium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing liquid comprises silicon dioxide abrasive particles, oxalic acid, potassium fluoride, water and a pH adjuster; Or, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, glycine, potassium fluoride, water and a pH adjuster; Alternatively, the chemical mechanical polishing solution comprises silicon dioxide abrasive particles, methanesulfonic acid, sodium fluoride, water and a pH adjuster.

7. The use according to claim 1, characterized in that: The polishing liquid also includes a bactericide.

8. The use according to claim 1, characterized in that: The preparation method of the chemical mechanical polishing liquid comprises: Mixing silicon dioxide with water to obtain agent A; mixing a polishing accelerator with water to obtain agent B; Agent A and agent B are mixed and the pH is adjusted to obtain a chemical mechanical polishing solution.

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