Composite abrasive polishing solution for lithium tantalate CMP (chemical mechanical polishing) and preparation method of composite abrasive polishing solution

Abstract

The invention relates to the technical field of polishing solutions, in particular to a composite abrasive polishing solution for lithium tantalate CMP (chemical mechanical polishing) and a preparation method of the composite abrasive polishing solution. The polishing solution comprises the following components in percentage by weight: 20%-40% of a composite abrasive, 0.5%-2% of a dispersing agent, 0.5%-5% of a chelating agent, 1%-10% of an oxidizing agent, 0.1%-1.5% of an anionic surfactant and the balance of water. In addition, the composite abrasive comprises at least two of sodium aluminosilicate, aluminum oxide, zirconium oxide and cerium oxide. Through the chemical mechanical polishing solution provided by the invention, the single-sided rough polishing rate of lithium tantalate can reach 15 [mu] m / h or above, and the surface roughness Sa can reach 0.3 nm. According to the lithium tantalate rough machining technology, the polishing rate is remarkably increased, high plane precision and no damage to the surface of a product are achieved on the basis of efficient polishing, the polishing solution is simple and convenient to prepare and operate, industrialization is easy to achieve, the PH value is neutral and slightly alkalescent, the universality to equipment is high, and the polishing solution is suitable for the field of efficient polishing of lithium tantalate.

Description

Technical Field

[0001] The invention relates to the technical field of polishing liquids, in particular to a composite abrasive polishing liquid for lithium tantalate CMP polishing and a preparation method thereof. Background Art

[0002] Lithium tantalate is a typical multifunctional single crystal material with a melting point of 1670°C, a hardness of 5.5 on the Mohs scale, and a density of 7.45 g / cm 2 Its piezoelectric strain constant d 22 2.4x10 -11 C / N,d 33为 0.8x10 -11 CN, thermal expansion coefficient (a) 16.1x10 -5 / ℃、(c)4.1x10 -8 / ℃, typical directions are X, Z, Y36°, Y42°, Y128°. It has excellent piezoelectric, electro-optical and thermoelectric properties such as large electromechanical coupling coefficient, low loss, high temperature stability and good high frequency performance. In order to obtain high-performance electronic components, the surface lattice of lithium tantalate wafers must be complete, with extremely high flatness, undamaged ultra-smooth surface and no crystal deviation. Even if there are tiny defects on the polished surface, it will destroy the surface properties of the crystal material and even cause changes in the crystal structure, affecting the frequency accuracy and frequency stability of the component. Lithium tantalate single crystal material is a typical hard and brittle material, and has mechanical properties such as cleavage and anisotropy. It is difficult to obtain a high-precision, undamaged wafer surface by grinding and polishing.

[0003] Regarding the research on ultra-smooth and damage-free surface polishing technology of lithium tantalate wafers, patent CN107665813A discloses a method for processing lithium tantalate crystal substrates. The patent uses diamond polishing liquid in both the rough polishing and fine polishing steps to achieve a mirror polishing effect, but the cost of the diamond liquid is extremely high and the surface roughness after rough polishing can only reach 50nm. Patent CN109988509A provides a lithium tantalate reduction sheet polishing liquid. The polishing liquid in the patent is prepared by combining specific nucleophilic reagents and oxidizing reagents in a reasonable manner. The polishing rate of this polishing liquid can reach up to 9.43μm / h, but the preparation process of the polishing liquid is complicated, and the patent does not mention what level the surface can reach after polishing. Patent CN107378654A discloses a polishing method for lithium tantalate substrates. The polishing method in the patent is to use chemical etching first and then single-sided polishing to make the roughness of the lithium tantalate wafer less than 0.5nm to obtain a lithium tantalate single-polished wafer. The chemical etching time in this method is as long as 1-16 hours, and the chemical etching itself will cause surface pits and other defects to the lithium tantalate wafer, and also cause great damage to the equipment. At present, lithium tantalate wafers still have problems such as low processing efficiency and yield rate, and difficult to control processing quality in actual production. Summary of the invention

[0004] The purpose of the present invention is to provide a composite abrasive polishing liquid for lithium tantalate CMP polishing and a preparation method thereof in view of the problems existing in the prior art.

[0005] In order to achieve the above object, the technical solution provided by the present invention is as follows:

[0006] A composite abrasive polishing liquid for CMP polishing of lithium tantalate, characterized in that the polishing liquid is composed of the following raw materials: composite abrasive content is 20%-40% wt, dispersant content is 0.5%-2% wt, chelating agent content is 0.5%-5% wt, oxidant content is 1%-10% wt, anionic surfactant content is 0.1%-1.5% wt, the balance is water, and the pH of the polishing liquid is 8-10. The single-side rough polishing rate of lithium tantalate is above 15 μm / h, and the surface roughness Sa can reach 0.3 nm.

[0007] Preferably, the composite abrasive is at least two of sodium aluminosilicate, aluminum oxide, zirconium oxide, and cerium oxide.

[0008] Preferably, the dispersant is one or more of sodium hexametaphosphate, sodium pyrophosphate, and sodium polyacrylate.

[0009] Preferably, the chelating agent is one or more of disodium ethylenediaminetetraacetic acid, hydroxyethylidene diphosphonic acid, and citric acid.

[0010] Preferably, the oxidant is one or more of potassium iodate, sodium hypochlorite and potassium persulfate.

[0011] Preferably, the anionic surfactant is one or more of sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether, and polyacrylamide.

[0012] A method for preparing a composite abrasive polishing liquid for lithium tantalate CMP polishing, characterized in that it comprises the following steps:

[0013] Step 1, weigh 0.5%-2% of dispersant and 0.5%-5% of chelating agent, add to 41.5%-77.9% of deionized water, and stir evenly;

[0014] Step 2, weigh 1%-10% of the oxidant, add it to the solution in step 1, and stir evenly;

[0015] Step 3, weigh 0.1%-1.5% of anionic surfactant, add it to the solution in step 2, and stir evenly;

[0016] Step 4, weigh 20%-40% of the composite abrasive and add it to the solution of step 3, stir evenly, and filter through a 300-mesh nylon sieve;

[0017] Step 5: Stir the abrasive solution obtained in step 4 again to obtain a composite abrasive polishing liquid for lithium tantalate CMP polishing with a pH value of 8-10.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention develops a composite abrasive polishing liquid for CMP polishing of lithium tantalate, wherein the pH value of the slurry is 8-10, the single-side rough polishing rate of lithium tantalate is above 15 μm / h, the surface roughness Sa can reach 0.3 nm, and efficient polishing of the surface of high-precision and non-damaged products can be achieved. The neutral to weakly alkaline polishing liquid has high versatility for the equipment used, the raw materials used are easy to handle, there is no pollution to the environment, the production process is simple, and it is easy to be industrialized. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a surface roughness picture of sample 1# in Example 1 of the present invention;

[0021] Figure 2 This is a surface roughness image of sample 2# in Example 1 of the present invention;

[0022] Figure 3 This is a surface roughness image of sample 3# in Example 1 of the present invention;

[0023] Figure 4 This is a surface roughness image of sample 4# in Example 2 of the present invention;

[0024] Figure 5 This is a surface roughness picture of sample 5# in Example 2 of the present invention;

[0025] Figure 6 This is a surface roughness picture of sample 6# in Example 2 of the present invention;

[0026] Figure 7 This is a surface roughness picture of sample 7# in Example 3 of the present invention;

[0027] Figure 8 This is a surface roughness picture of sample 8# in Example 3 of the present invention;

[0028] Fig. 9 This is a surface roughness picture of sample 9# in Example 3 of the present invention;

[0029] Fig.10 This is a surface roughness image of sample 10# in Example 3 of the present invention;

[0030] Fig.11 This is a surface roughness picture of sample 11# in Example 4 of the present invention;

[0031] Fig.12 This is a surface roughness picture of sample 12# in Example 4 of the present invention;

[0032] Fig.13 This is a graph showing the average polishing rate of composite abrasives of the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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.

[0034] The prepared lithium tantalate polishing liquid, all embodiments were compared and tested according to the following conditions and polishing parameters:

[0035]

[0036] Example 1

[0037] The lithium tantalate polishing liquid prepared in this embodiment is prepared by the following method:

[0038] Step 1, weigh three portions of 0.5% wt sodium hexametaphosphate and 5% wt disodium ethylenediaminetetraacetate, respectively, add them into 69.4%, 59.4%, and 49.4% deionized water, respectively, to obtain solutions 1#, 2#, and 3#, respectively, and stir evenly;

[0039] Step 2, weigh three portions of 5% wt potassium iodate, add them to solutions 1#, 2#, and 3# obtained in step 1 respectively, and stir evenly;

[0040] Step 3, weigh three portions of 0.1% Wt fatty alcohol polyoxyethylene ether, add them to the solutions 1#, 2#, and 3# obtained in step 2, respectively, and stir evenly;

[0041] Step 4: first weigh three portions of 10% wt sodium aluminosilicate and add them to solutions 1#, 2#, and 3# obtained in step 3 and stir evenly; then weigh 10% wt aluminum oxide, 20% wt zirconium oxide, and 30% wt cerium oxide abrasives respectively, add them to solutions 1#, 2#, and 3# in sequence, and stir evenly in the solution;

[0042] Step 5, the abrasive solution obtained in step 4 is stirred again and the pH is adjusted to 9 to obtain the lithium tantalate polishing solution.

[0043] The results show that in Example 1, the removal amount of sample 1# is 15.79μm / h, and the surface roughness Sa is 0.356nm; the removal amount of sample 2# is 17.87μm / h, and the surface roughness Sa is 0.306nm; the removal amount of sample 3# is 19.45μm / h, and the surface roughness Sa is 0.272nm.

[0044] Example 2

[0045] The lithium tantalate polishing liquid prepared in this embodiment is prepared by the following method:

[0046] Step 1, weigh three portions of 2% wt sodium polyacrylate and 0.5% wt hydroxyethylidene diphosphonic acid, respectively, add them into 66%, 56%, and 66% deionized water, respectively, to obtain solutions 4#, 5#, and 6#, and stir evenly;

[0047] Step 2, weigh three portions of 1% wt potassium persulfate, add them to the solutions 4#, 5#, and 6# obtained in step 1 respectively, and stir evenly;

[0048] Step 3, weigh three portions of 0.5% wt sodium dodecylbenzene sulfonate, add them to solutions 4#, 5#, and 6# obtained in step 2, respectively, and stir evenly;

[0049] Step 4: Weigh three portions of 10% wt zirconium oxide and add them to solutions 4#, 5#, and 6# obtained in step 3 and stir evenly. Then weigh 20% wt sodium aluminosilicate, 30% wt aluminum oxide, and 20% wt cerium oxide abrasives respectively, and add them to solutions 4#, 5#, and 6# in turn, and stir evenly in the solution.

[0050] Step 5, the abrasive solution obtained in step 4 is stirred again and the pH is adjusted to 9 to obtain the lithium tantalate polishing solution.

[0051] The results show that in Example 2, the removal amount of sample 4# is 17.46μm / h, and the surface roughness Sa is 0.319nm; the removal amount of sample 5# is 18.69μm / h, and the surface roughness Sa is 0.292nm; the removal amount of sample 6# is 16.58μm / h, and the surface roughness Sa is 0.332nm.

[0052] Example 3

[0053] The lithium tantalate polishing liquid prepared in this embodiment is prepared by the following method:

[0054] Step 1, weigh three portions of 1% wt sodium pyrophosphate and 2.5% wt citric acid, add them into 45%, 55%, and 45% deionized water respectively, to obtain solutions 7#, 8#, and 9# in sequence, and stir evenly;

[0055] Step 2, weigh three portions of 10% wt sodium hypochlorite, add them to solutions 7#, 8#, and 9# obtained in step 1 respectively, and stir evenly;

[0056] Step 3, weigh three portions of 1.5% Wt polyacrylamide, add them to the solutions 7#, 8#, and 9# obtained in step 2, respectively, and stir evenly;

[0057] Step 4: Weigh three portions of 10% wt cerium oxide and add them to solutions 7#, 8#, and 9# obtained in step 3 and stir evenly. Then weigh 30% wt sodium aluminosilicate, 20% wt aluminum oxide, and 30% wt zirconium oxide abrasives respectively, add them to solutions 7#, 8#, and 9# in sequence, and stir evenly in the solution.

[0058] Step 5, the abrasive solution obtained in step 4 is stirred again and the pH is adjusted to 9 to obtain the lithium tantalate polishing solution.

[0059] The results show that in Example 3, the removal amount of sample 7# is 19.89μm / h, and the surface roughness Sa is 0.270nm; the removal amount of sample 8# is 16.27μm / h, and the surface roughness Sa is 0.336nm; the removal amount of sample 9# is 19.13μm / h, and the surface roughness Sa is 0.278nm.

[0060] Example 4

[0061] The lithium tantalate polishing liquid prepared in this embodiment is prepared by the following method:

[0062] Step 1, weigh three portions of 1.5% wt sodium hexametaphosphate and 3% wt hydroxyethylidene diphosphonic acid, respectively, add them into 60.5%, 50.5%, and 70.5% deionized water, respectively, to obtain solutions 10#, 11#, and 12#, respectively, and stir evenly;

[0063] Step 2, weigh three portions of 4% wt sodium hypochlorite, add them to the solutions 10#, 11#, and 12# obtained in step 1, respectively, and stir evenly;

[0064] Step 3, weigh three portions of 1% Wt fatty alcohol polyoxyethylene ether, add them to the solutions 10#, 11#, and 12# obtained in step 2, respectively, and stir evenly;

[0065] Step 4: Weigh three portions of 10% Wt aluminum oxide and add them to the solutions 10#, 11#, and 12# obtained in step 3 and stir evenly; then weigh 20% Wt sodium aluminosilicate, 30% Wt zirconium oxide, and 10% Wt cerium oxide abrasives respectively, and add them to 10#, 11#, and 12# in sequence, and stir evenly in the solution;

[0066] Step 5, the abrasive solution obtained in step 4 is stirred again and the pH is adjusted to 9 to obtain the lithium tantalate polishing solution.

[0067] The results show that in Example 4, the removal amount of sample 10# is 16.91μm / h, and the surface roughness Sa is 0.330nm; the removal amount of sample 11# is 18.84μm / h, and the surface roughness Sa is 0.289nm; the removal amount of sample 12# is 15.36μm / h, and the surface roughness Sa is 0.341nm. The comparative test data of the embodiments are as follows:

[0068]

[0069]

[0070] Comparative Examples and Test Result Analysis:

[0071] When the content of composite abrasive is between 20% and 40%, the polishing rate can reach above 15μm / h. As the content of composite abrasive increases, the rate increases and the surface roughness decreases.

[0072] From the perspective of the composition of the composite abrasive, the combination of sodium aluminosilicate and cerium oxide has a better polishing effect than other abrasive combinations. Fig.13 ;

[0073] From the perspective of the ratio of composite abrasives, although the polishing effect of sodium aluminosilicate combined with cerium oxide is better than other combinations, the polishing effect of sodium aluminosilicate and cerium oxide when used in a 1:3 ratio is not as good as that of 3:1. Cerium oxide is more active than sodium aluminosilicate. This polishing liquid also contains chelating agents and oxidants, so the physical effect of the abrasive is relatively strong, which has a good effect on the polishing effect.

[0074] A comprehensive comparison of the 12 samples shows that sample 7 has the best performance, with a polishing rate MRR of 19.89 μm / h and a surface roughness Sa of 0.270 nm.

[0075] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A composite abrasive polishing liquid for lithium tantalate CMP polishing, characterized in that: The polishing liquid is composed of the following raw materials: a composite abrasive content of 20%-40% wt, a dispersant content of 0.5%-2% wt, a chelating agent content of 0.5%-5% wt, an oxidant content of 1%-10% wt, an anionic surfactant content of 0.1%-1.5% wt, and the balance is water, and the pH of the polishing liquid is 8-10.

2. The composite abrasive polishing liquid for lithium tantalate CMP polishing according to claim 1, characterized in that: The composite abrasive is at least two of sodium aluminosilicate, aluminum oxide, zirconium oxide and cerium oxide.

3. The composite abrasive polishing liquid for lithium tantalate CMP polishing according to claim 1, characterized in that: The dispersant is one or more of sodium hexametaphosphate, sodium pyrophosphate and sodium polyacrylate.

4. The composite abrasive polishing liquid for lithium tantalate CMP polishing according to claim 1, characterized in that: The chelating agent is one or more of disodium ethylenediaminetetraacetate, hydroxyethylidene diphosphonic acid and citric acid.

5. The composite abrasive polishing liquid for lithium tantalate CMP polishing according to claim 1, characterized in that: The oxidant is one or more of potassium iodate, sodium hypochlorite and potassium persulfate.

6. The composite abrasive polishing liquid for lithium tantalate CMP polishing according to claim 1, characterized in that: The anionic surfactant is one or more of sodium dodecylbenzene sulfonate, fatty alcohol polyoxyethylene ether and polyacrylamide.

7. A method for preparing a composite abrasive polishing liquid for lithium tantalate CMP polishing, characterized in that: The following steps are involved: Step 1, weigh 0.5%-2% of dispersant and 0.5%-5% of chelating agent, add to 41.5%-77.9% of deionized water, and stir evenly; Step 2, weigh 1%-10% of the oxidant, add it to the solution in step 1, and stir evenly; Step 3, weigh 0.1%-1.5% of anionic surfactant, add it to the solution in step 2, and stir evenly; Step 4, weigh 20%-40% of the composite abrasive and add it to the solution of step 3, stir evenly, and filter through a 300-mesh nylon sieve; Step 5: Stir the abrasive solution obtained in step 4 again to obtain a composite abrasive polishing liquid for lithium tantalate CMP polishing with a pH value of 8-10.

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