Polishing solution for lithium niobate CMP (Chemical Mechanical Polishing) and preparation method thereof

Abstract

The invention discloses a polishing solution for lithium niobate CMP (Chemical Mechanical Polishing). The polishing solution is prepared from the following raw materials in percentage by weight: 10 to 30 percent of grinding material, 0.1 to 2 percent of dispersing agent, 1 to 3 percent of lubricating agent, 0.1 to 3 percent of chelating agent, 0.5 to 2 percent of surfactant and the balance of water. Through the chemical mechanical polishing solution provided by the invention, the single-sided rough polishing rate of lithium niobate can reach 12 [mu] m / h or above, the optimal single-sided rough polishing rate can reach 20 [mu] m / h, and the optimal surface roughness Sa can reach 0.9 nm or below. According to the lithium niobate rough machining technology, the polishing rate is remarkably increased, and high-precision polishing without surface defects is achieved on the basis of efficient polishing. Compared with the prior art, the method has the beneficial effects that the operation process is simple and convenient, industrialization is easy to realize, the polishing solution is neutral and slightly alkalescent, the universality to equipment is high, and the method is suitable for the field of efficient polishing of lithium niobate.

Description

Technical Field

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

[0002] The Mohs hardness of lithium niobate crystal is 5, which is between the first generation of hard and brittle semiconductors (typically represented by silicon) and the third generation of soft and brittle semiconductors (typically represented by mercury cadmium telluride). It has unique mechanical properties, and its processing mechanism is essentially different from the above two. Before lithium niobate crystals are made into high-performance devices, they need to go through the following steps: first, prepare a single crystal ingot, and then cut it into wafers from the single crystal ingot. In this process, subsurface damage will occur, and ultra-precision methods are required to remove the damage layer to obtain a high-quality, damage-free and smooth surface. Lithium niobate crystal is a functional material with multiple properties such as ferroelectric, piezoelectric, thermoelectric, electro-optical, acoustoelectric and photorefractive effects. It is currently recognized as one of the main candidate materials for "optical silicon" in the optoelectronic era. It has been widely used in ultrasonic devices, optical switches, optical communication modulators, second harmonic generation and optical parametric oscillators. The processing quality and precision of lithium niobate wafers directly affect the performance of their devices. Therefore, the application of lithium niobate requires that the wafer surface is ultra-smooth, defect-free and free of metamorphic layers. At present, there is little research on the processing characteristics of lithium niobate wafers and their ultra-smooth surface processing technology, which restricts the development and application of lithium niobate products.

[0003] Some scholars have also conducted corresponding research on the use of CMP to process lithium niobate wafers. Patent CN118305647A discloses a polishing method for lithium niobate. The key point of this patent is to use coarse grinding and fine grinding to polish the lithium niobate section to achieve a lower roughness. The defect of this patent is that the oxidant used is highly corrosive, and the surface roughness is as low as 1.33nm, which is only at the sub-nanometer level. Patent CN113714889A discloses a large-size ultra-thin high-precision lithium niobate wafer edge processing method. This patent mainly uses a brush to perform precision processing on the edge of lithium niobate to achieve the nanometer level. The defect of this patent is that for the nanometer-level technology of lithium niobate, it can only be processed at the edge, and it is impossible to achieve comprehensive polishing of the surface accuracy of lithium niobate. Summary of the invention

[0004] The purpose of the present invention is to provide a polishing liquid for lithium niobate 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 polishing liquid for CMP polishing of lithium niobate, characterized in that the polishing liquid is composed of the following raw materials: an abrasive content of 10%-30%Wt, a dispersant content of 0.1%-2%Wt, a lubricant content of 1%-3%Wt, a chelating agent content of 0.1%-3%Wt, a surfactant content of 0.5%-2%Wt, and the balance is water, and the pH of the polishing liquid is 8-11, the single-sided rough polishing rate of lithium niobate can reach more than 12μm / h, the optimal single-sided rough polishing rate can reach 20μm / h, and the optimal surface roughness Sa can reach less than 0.9nm.

[0007] Preferably, the abrasive is one or more of aluminum oxide, cerium oxide, and zirconium oxide.

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

[0009] Preferably, the lubricant is one or more of glycerol, polyglycerol decaglycerol and triethylene glycol.

[0010] Preferably, the chelating agent is one or more of disodium ethylenediaminetetraacetate, tetrasodium hydroxyethylidene diphosphonate, and malic acid.

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

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

[0013] Step 1, weigh 0.1%-2% of dispersant and 0.1%-3% of chelating agent, add them into 60%-88.3% of deionized water, and stir evenly;

[0014] Step 2, weigh 0.5%-2% of a surfactant and 1%-3% of a lubricant, add them to the solution of step 1, and stir evenly;

[0015] Step 3, weigh 10%-30% of the abrasive and add it to the solution in step 2, stir evenly, and filter through a 400-mesh stainless steel sieve;

[0016] Step 4: fully and evenly stir the abrasive solution obtained in step 3, and the pH value is 8-11, which is the rough processing polishing liquid for chemical mechanical polishing of lithium niobate.

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

[0018] The present invention provides a polishing liquid for rough machining of lithium niobate, wherein the pH of the slurry is 8-11, the single-side rough polishing rate of lithium niobate can reach more than 12 μm / h, the optimal single-side rough polishing rate can reach 20 μm / h, and the optimal surface roughness Sa can reach less than 0.9 nm. 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 industrialize. It has the characteristics of fast polishing rate, high surface accuracy, etc., and is suitable for the field of efficient polishing of lithium niobate rough machining. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a surface roughness picture of sample 1# in Example 1 of the present invention;

[0020] Figure 2 This is a surface roughness image of sample 2# in Example 1 of the present invention;

[0021] Figure 3 This is a surface roughness image of sample 3# in Example 1 of the present invention;

[0022] Figure 4 This is a surface roughness image of sample 4# in Example 2 of the present invention;

[0023] Figure 5 This is a surface roughness picture of sample 5# in Example 2 of the present invention;

[0024] Figure 6 This is a surface roughness picture of sample 6# in Example 2 of the present invention;

[0025] Figure 7 This is a surface roughness picture of sample 7# in Example 3 of the present invention;

[0026] Figure 8 This is a surface roughness picture of sample 8# in Example 3 of the present invention;

[0027] Fig. 9 This is a surface roughness picture of sample 9# in Example 3 of the present invention;

[0028] Fig.10 This is a surface roughness image of sample 10# in Example 3 of the present invention;

[0029] Fig.11 This is a surface roughness picture of sample 11# in Example 4 of the present invention;

[0030] Fig.12 This is a surface roughness picture of sample 12# in Example 4 of the present invention;

[0031] Fig.13 This is a surface roughness picture of sample 13# in Example 4 of the present invention;

[0032] Fig.14 This is a surface roughness picture of sample 14# in Example 5 of the present invention;

[0033] Fig.15 This is a surface roughness image of sample 15# in Example 5 of the present invention;

[0034] Fig.16 This is a surface roughness picture of sample 16# in Example 5 of the present invention;

[0035] Fig.17 This is a surface roughness image of sample 17# in Example 6 of the present invention;

[0036] Fig.18 This is a surface roughness picture of sample 18# in Example 6 of the present invention;

[0037] Fig.19 This is a surface roughness image of sample 19# in Example 6 of the present invention;

[0038] Fig. 20 This is a surface roughness picture of sample 20# in Example 6 of the present invention. DETAILED DESCRIPTION

[0039] 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.

[0040] The prepared lithium niobate polishing liquid, all embodiments were tested for comparison according to the following conditions and polishing parameters:

[0041]

[0042]

[0043] Example 1

[0044] The lithium niobate polishing liquid prepared in this embodiment is prepared by the following method:

[0045] Step 1, weigh 3 parts of 0.1% wt sodium hexametaphosphate, 0.1% wt disodium ethylenediaminetetraacetate, 0.5% wt sodium stearate, and 2% wt glycerol, respectively add them into 3 parts of 69.3% deionized water to obtain solutions 1#, 2#, and 3# in turn, and stir evenly;

[0046] Step 2, weigh 30% of aluminum oxide, zirconium oxide, and cerium oxide abrasives respectively, and add them to the 1#, 2#, 3#, and solutions in step 1 respectively;

[0047] Step 3: Stir the abrasive solution obtained in step 2 evenly and adjust the pH to 10 with potassium hydroxide to obtain the lithium niobate polishing solution.

[0048] The results show that in Example 1, the removal amount of sample 1# is 12.07μm / h, and the surface roughness Sa is 3.293nm; the removal amount of sample 2# is 14μm / h, and the surface roughness Sa is 1.736nm; the removal amount of sample 3# is 14.5μm / h, and the surface roughness Sa is 2.156nm.

[0049] Example 2

[0050] The lithium niobate polishing liquid prepared in this embodiment is prepared by the following method:

[0051] Step 1, weigh 3 parts of 2% wt sodium polyacrylate, 3% wt malic acid, 1% wt sodium polyoxyethylene fatty alcohol ether sulfate, and 1% wt polyglycerol ten, add them into 63%, 73%, and 83% deionized water respectively, to obtain solutions 4#, 5#, and 6# in turn, and stir evenly;

[0052] Step 2, weigh 30%, 20%, and 10% of abrasive (zirconia is used as a uniform abrasive), add them to the 4#, 5#, and 6# solutions in step 1, and stir evenly;

[0053] Step 3: Stir the abrasive solution obtained in step 2 evenly and adjust the pH to 10 with potassium hydroxide to obtain the lithium niobate polishing solution.

[0054] The results show that in Example 2, the removal amount of sample 4# is 16.21μm / h, and the surface roughness Sa is 1.337nm; the removal amount of sample 5# is 14.58μm / h, and the surface roughness Sa is 1.139nm; the removal amount of sample 6# is 12.97μm / h, and the surface roughness Sa is 1.110nm.

[0055] Example 3

[0056] The lithium niobate polishing liquid prepared in this embodiment is prepared by the following method:

[0057] Step 1, weigh 4 parts of 1% wt sodium tripolyphosphate, 1.5% wt tetrasodium hydroxyethylidene diphosphonate, and 3% wt triethylene glycol, add them into 73% deionized water respectively, and obtain solutions 7#, 8#, 9#, and 10# in sequence, and stir evenly;

[0058] Step 2, weigh 1.5% wt sodium stearate, 1.5% wt sodium allyl sulfonate, 1.5% wt sodium dodecylbenzene sulfonate, and 1.5% wt sodium polyoxyethylene fatty alcohol ether sulfate, and add them to step 1 in sequence to obtain solutions 7#, 8#, 9#, and 10#;

[0059] Step 3: Weigh 20% wt of zirconium oxide and add it to the solution obtained in step 2, and adjust the pH to 10 with potassium hydroxide to obtain the lithium niobate polishing solution.

[0060] The results show that: the removal amount of sample 7# in Example 3 is 16.32μm / h, and the surface roughness Sa is 1.030nm; the removal amount of sample 8# is 17.69μm / h, and the surface roughness Sa is 0.977nm; the removal amount of sample 9# is 15.43μm / h, and the surface roughness Sa is 1.179nm; the removal amount of sample 10# is 13.29μm / h, and the surface roughness Sa is 1.432nm.

[0061] Example 4

[0062] The lithium niobate polishing liquid prepared in this embodiment is prepared by the following method:

[0063] Step 1, weigh 3 parts of 0.5% Wt sodium hexametaphosphate, 2% Wt malic acid, and 2.5% Wt glycerol, add them into 74.5%, 74%, and 73% deionized water, respectively, to obtain solutions 11#, 12#, and 13#, respectively, and stir evenly;

[0064] Step 2: Weigh 0.5%, 1%, and 2% of sodium allyl sulfonate respectively, and add them to the 11#, 12#, and 13# solutions in step 1 respectively, and stir evenly;

[0065] Step 3: Weigh 20% wt of zirconium oxide and add it to the solution obtained in step 2, and adjust the pH to 10 with potassium hydroxide to obtain the lithium niobate polishing solution.

[0066] The results show that in Example 4, the removal amount of sample 11# is 16.47μm / h, and the surface roughness Sa is 0.929nm; the removal amount of sample 12# is 18.03μm / h, and the surface roughness Sa is 1.035nm; the removal amount of sample 13# is 16.32μm / h, and the surface roughness Sa is 0.873nm.

[0067] Example 5

[0068] The lithium niobate polishing liquid prepared in this embodiment is prepared by the following method:

[0069] Step 1, weigh 3 parts of 1.5% wt sodium polyacrylate, 1% wt sodium allyl sulfonate, and 2% wt polyglycerol ten, respectively add them into 75.5% deionized water to obtain solutions 14#, 15#, and 16# in sequence, and stir evenly;

[0070] Step 2, weigh 0.5% wt of disodium ethylenediaminetetraacetate, tetrasodium hydroxyethylidene diphosphonate, and malic acid, and add them to step 1 in sequence to obtain solutions 14#, 15#, and 16#;

[0071] Step 3: Weigh 20% wt of zirconium oxide and add it to the solution obtained in step 2, and adjust the pH to 10 with potassium hydroxide to obtain the lithium niobate polishing solution.

[0072] The results show that: the removal amount of sample 14# in Example 5 is 19.64μm / h, and the surface roughness Sa is 0.981nm; the removal amount of sample 15# is 17.28μm / h, and the surface roughness Sa is 0.897nm; the removal amount of sample 16# is 16.93μm / h, and the surface roughness Sa is 0.868nm.

[0073] Example 6

[0074] The lithium niobate polishing liquid prepared in this embodiment is prepared by the following method:

[0075] Step 1, weigh 4 parts of 2% wt sodium tripolyphosphate, 1% wt sodium allyl sulfonate, and 1.5% wt triethylene glycol, add them into 75.4%, 75%, 74%, and 72.5% deionized water, respectively, to obtain solutions 17#, 18#, 19#, and 20#, respectively, and stir evenly;

[0076] Step 2: Weigh 0.1%, 0.5%, 1.5%, and 3% of disodium ethylenediaminetetraacetate, respectively, and add them to the 17#, 18#, 19#, and 20# solutions in step 1, respectively, and stir evenly;

[0077] Step 3: Weigh 20% wt of zirconium oxide and add it to the solution obtained in step 2, and adjust the pH to 10 with potassium hydroxide to obtain the lithium niobate polishing solution.

[0078] The results show that: the removal amount of sample 17# in Example 6 is 17.49μm / h, and the surface roughness Sa is 1.213nm; the removal amount of sample 18# is 20.56μm / h, and the surface roughness Sa is 0.940nm; the removal amount of sample 19# is 21.37μm / h, and the surface roughness Sa is 0.845nm; the removal amount of sample 20# is 18.96μm / h, and the surface roughness Sa is 0.808nm.

[0079] The comparative test data of the embodiment are as follows:

[0080]

[0081]

[0082] Comparative Examples and Test Result Analysis: In combination with the three samples of Example 1, among the three abrasives, the polishing rate of cerium oxide is outstanding and is almost the same as that of aluminum oxide. Although the polishing rate of zirconium oxide is not as fast as that of cerium oxide and aluminum oxide, the surface roughness of zirconium oxide is the lowest; In combination with the three samples of Example 2, it can be clearly seen that as the abrasive content decreases, the polishing rate decreases accordingly. With the reduction of the abrasive content, the particle size in the polishing liquid decreases, the surface defects caused also decrease, and the surface roughness becomes better and better; In combination with the four samples of Example 3, it can be clearly seen that among the four surfactants, sodium allyl sulfonate as a surfactant has better polishing effect than the other three surfactants in terms of polishing rate and surface roughness, but the other three surfactants can also achieve the required polishing effect; In combination with the three samples of Example 4, as the surfactant With the increase of surfactant content, the polishing rate shows a trend of first increasing and then decreasing, and reaches the peak value of the peak rate when the surfactant content is 1%, and the surface roughness also shows a trend of first increasing and then decreasing; combined with the three samples of Example 5, in the selection of chelating agents, the polishing rate of disodium ethylenediaminetetraacetic acid is better than that of the other two chelating agents. Although the polishing rate of disodium ethylenediaminetetraacetic acid is much greater than that of the other two chelating agents, the polishing rates of the other two chelating agents also meet the polishing rates we require; combined with the four samples of Example 6, with the increase of chelating agent content, the surface roughness shows a trend of gradually decreasing, but the polishing rate shows a trend of first increasing and then decreasing, and the polishing rate reaches the peak value when the content is 1.5%; comprehensive comparison of 20 samples, the best performance is sample 19, the polishing rate MRR is 21.37μm / h, and the surface roughness Sa is 0.845nm.

[0083] 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 polishing liquid for lithium niobate CMP polishing, characterized in that: The polishing liquid is composed of the following raw materials: an abrasive content of 10%-30% wt, a dispersant content of 0.1%-2% wt, a lubricant content of 1%-3% wt, a chelating agent content of 0.1%-3% wt, a surfactant content of 0.5%-2% wt, and the balance is water, and the pH of the polishing liquid is 8-11.

2. The polishing liquid for lithium niobate CMP polishing according to claim 1, characterized in that: The abrasive is one or more of aluminum oxide, cerium oxide and zirconium oxide.

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

4. The polishing liquid for lithium niobate CMP polishing according to claim 1, characterized in that: The lubricant is one or more of glycerol, polyglycerol decaglycol and triethylene glycol.

5. The polishing liquid for lithium niobate CMP polishing according to claim 1, characterized in that: The chelating agent is one or more of disodium ethylenediaminetetraacetate, tetrasodium hydroxyethylidene diphosphonate, and malic acid.

6. The polishing liquid for lithium niobate CMP polishing according to claim 1, characterized in that: The surfactant is one or more of sodium stearate, sodium allyl sulfonate, sodium dodecylbenzene sulfonate, and sodium fatty alcohol polyoxyethylene ether sulfate.

7. A method for preparing a polishing liquid for lithium niobate CMP polishing, characterized in that: The following steps are involved: Step 1, weigh 0.1%-2% of dispersant and 0.1%-3% of chelating agent, add to 60%-88.3% of deionized water, and stir evenly; Step 2, weigh 0.5%-2% of a surfactant and 1%-3% of a lubricant, add them to the solution of step 1, and stir evenly; Step 3, weigh 10%-30% of the abrasive and add it to the solution in step 2, stir evenly, and filter through a 400-mesh stainless steel sieve; Step 4: fully and evenly stir the abrasive solution obtained in step 3, and the pH value is 8-11, which is the rough processing polishing liquid for chemical mechanical polishing of lithium niobate.

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