Alumina polishing liquid and preparation method thereof

Abstract

The present invention relates to the field of polishing technology, and in particular to an aluminum oxide polishing liquid and a preparation method thereof. The present invention discloses an aluminum oxide polishing liquid and a preparation method thereof, wherein the aluminum oxide polishing liquid comprises aluminum oxide, an oxidant and an additive; the additive is compounded by a modifier and a dispersant; the mass ratio of the modifier and the dispersant is (0.8-1): (1-0.75); the modifier is polyvinyl pyrrolidone; the dispersant comprises at least one of sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyacrylic acid and polyacrylate. The present invention has a strong dispersing and suspending ability for aluminum oxide by compounding a modifier and a dispersant, so that the polishing liquid of the present invention has good polishing efficiency and surface quality.

Description

Technical Field

[0001] The invention relates to the technical field of polishing, and in particular to an aluminum oxide polishing liquid and a preparation method thereof. Background Art

[0002] Chemical mechanical polishing (CMP) is the best known method for flattening the polishing surface. The performance of the polishing liquid plays a very important role and influences the effect of CMP, especially the particle size and dispersion uniformity of the polishing abrasive in the polishing liquid directly affect the surface quality of the polishing. The main polishing abrasives are aluminum oxide, silicon dioxide, cerium oxide, silicon carbide, etc. Compared with SiO2 polishing liquid with a narrow particle size distribution range, its polishing efficiency is not high. Compared with SiO2 polishing liquid, aluminum oxide polishing liquid has high polishing efficiency, but it is easy to agglomerate and settle, and it is easy to scratch during the polishing process, affecting the stability of its polishing performance. Summary of the invention

[0003] The technical problem to be solved by the present invention is that the aluminum oxide polishing liquid has a high polishing efficiency, but it is easy to agglomerate and settle, and is easily scratched during the polishing process, which affects the stability of its polishing performance. The present invention provides an aluminum oxide polishing liquid and a preparation method thereof for solving the above problems. The present invention has a strong dispersing and suspending ability for aluminum oxide by compounding a modifier and a dispersant, so that the polishing liquid of the present invention has good polishing efficiency and surface quality.

[0004] The present invention is achieved through the following technical solutions:

[0005] An aluminum oxide polishing liquid comprises aluminum oxide, an oxidant and an additive; the additive is compounded by a modifier and a dispersant; the mass ratio of the modifier and the dispersant is (0.8-1):(1-0.75); the modifier is polyvinyl pyrrolidone; the dispersant comprises at least one of sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyethylene glycol, polyacrylic acid and polyacrylate.

[0006] The present invention selects a compound of a modifier and a dispersant, which, on the one hand, increases the dispersibility and suspension of aluminum oxide, making it less likely to precipitate and increasing the polishing effect; on the other hand, polyvinyl pyrrolidone can modify the surface of aluminum oxide, so that the hard aluminum oxide surface is covered with a soft film, so that the present invention has good polishing quality.

[0007] The present invention adopts the method of first dispersing and then modifying. The use of a dispersant with an appropriate content can make the aluminum oxide have better dispersibility, reduce abrasive agglomeration, increase the contact area between the abrasive and the modifier, and improve the modification rate. Too high a dispersant content will form multi-layer adsorption on the surface of the aluminum oxide, reduce the stability of the aluminum oxide suspension, increase agglomeration, reduce the polishing efficiency, and cause the surface quality of the polishing to deteriorate. Too low a dispersant content will prevent the aluminum oxide from being completely dispersed, resulting in the inability to stably control the surface quality of the polishing. Polyvinyl pyrrolidone is a hydrophilic, film-forming polymer. As a modifier, it can coat a thin film on the surface of the aluminum oxide and increase the affinity of the abrasive with water, reducing the agglomeration of the abrasive during the polishing process. If its content in the polishing liquid is too high, the stability of the entire polishing liquid system will deteriorate. If its content is too low, it cannot achieve full coating of the aluminum oxide, affecting the polishing effect.

[0008] In addition, the present invention uses aluminum oxide as the polishing abrasive. Compared with silicon dioxide, aluminum oxide has a greater hardness and a stronger grinding effect, which makes the present invention have a good polishing efficiency. Moreover, aluminum oxide is an amphoteric oxide, which can be used not only under acidic conditions but also under alkaline conditions, which makes the present invention have a wider range of applications.

[0009] Further optionally, the mass ratio of the modifier to the dispersant is 1:1.

[0010] Further optionally, the oxidant includes one or any combination of potassium dichromate, potassium persulfate, ammonium dichromate, and hydrogen peroxide.

[0011] Further optionally, the composition includes, by mass percentage, 2% to 30% aluminum oxide, 0.5% to 3% oxidant, 0.1% to 3% additive, and the rest is deionized water.

[0012] Further optionally, the composition is composed of 12% to 20% aluminum oxide, 1.5% to 2.5% oxidant, 1.2% to 2.5% additive, and the rest is deionized water.

[0013] Further optionally, the composition, by mass percentage, includes: 15% aluminum oxide, 2% oxidant, 2% additive, and the rest is deionized water.

[0014] Further optionally, the alumina crystal form is α-type, with an average particle size of 0.05 μm-5 μm and a specific surface area of ​​≥30 m / g.

[0015] The aluminum oxide in the polishing liquid of the present invention has an α-type crystal form, an average particle size of 0.05 μm-5 μm, and is in a white fluffy powder state; the specific surface area is ≥1m 2 / g; uniform particle size distribution, high purity, high dispersion, and high temperature resistance; nano alumina has strong heat resistance, good formability, stable crystal phase, high hardness, and good dimensional stability.

[0016] A method for preparing an aluminum oxide polishing liquid is used to prepare the above-mentioned aluminum oxide polishing liquid; firstly, an aluminum oxide abrasive is dispersed by a dispersant, then modified by a modifier, and finally treated by an oxidant to obtain the aluminum oxide polishing liquid.

[0017] The present invention selects a compound of a modifier and a dispersant, firstly uses the dispersant to disperse the aluminum oxide abrasive to obtain aluminum oxide particles with uniform particle size to avoid agglomeration; then performs a modification treatment to cover the hard aluminum oxide surface with a soft film, so that the present invention has good polishing quality.

[0018] Optionally, the method further comprises the steps of:

[0019] Step 1, mixing aluminum oxide abrasive and a dispersant to obtain a mixed material;

[0020] Step 2, adding polyvinyl pyrrolidone to the mixed material and mixing to obtain a modified mixed material;

[0021] Step 3, adding an oxidant to the mixed material, adjusting the pH, and obtaining an aluminum oxide polishing liquid.

[0022] Further optionally, in step 1 and / or step 2, dispersion and mixing are performed by ultrasound and / or mechanical stirring.

[0023] More specifically, the steps are as follows:

[0024] Alumina abrasive and dispersant are added under mechanical stirring and ultrasonically dispersed to obtain aluminum oxide polishing liquid.

[0025] Add appropriate amount of polyvinyl pyrrolidone to the alumina polishing liquid and stir ultrasonically to obtain modified alumina polishing liquid.

[0026] An aluminum oxide polishing liquid is obtained by adding a proper amount of an oxidant to the modified aluminum oxide polishing liquid and adjusting the pH value to a desired value.

[0027] The present invention has the following advantages and beneficial effects:

[0028] 1. The aluminum oxide modified with polyvinyl pyrrolidone in the present invention has better suspension stability and dispersibility; the aluminum oxide modified with polyvinyl pyrrolidone has a layer of soft polyvinyl pyrrolidone coated on the hard aluminum oxide surface, so that when the abrasive contacts the silicon wafer surface, direct contact is avoided, scratches are reduced, and better surface quality is obtained. Polyvinyl pyrrolidone has a moisturizing effect. The aluminum oxide modified with polyvinyl pyrrolidone has a better moisturizing effect, reduces the abrasive agglomeration caused by water evaporation during the polishing process, and obtains better surface quality.

[0029] 2. The present invention selects a compound of a modifier and a dispersant. The dispersant is first used to disperse the aluminum oxide abrasive to obtain aluminum oxide particles with uniform particle size to avoid agglomeration. Then a modification treatment is performed to cover the hard aluminum oxide surface with a soft film, so that the present invention has good polishing quality.

[0030] 3. Alumina polishing liquid has a greater removal rate than silica polishing liquid. Alumina polishing liquid can be used under acidic, neutral and alkaline conditions and has a wider range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0032] Figure 1 Particle size distribution of alumina polishing liquid without PVP added in control experiment 1.

[0033] Figure 2 This is the particle size distribution of alumina after adding PVP in Example 1. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0035] Example 1

[0036] This embodiment provides an aluminum oxide polishing liquid: the polishing liquid is composed of aluminum oxide abrasive, oxidant, modifier polyvinyl pyrrolidone, dispersant and pure water, and the mass percentage of each component is as follows:

[0037] Aluminum oxide abrasive 2%;

[0038] Ammonium dichromate 0.5%;

[0039] Polyvinylpyrrolidone 0.05%;

[0040] Polyacrylic acid 0.05%;

[0041] Pure water 97.4%.

[0042] Specifically prepared by the following method:

[0043] Step 1, adding aluminum oxide abrasive and dispersant under mechanical stirring, and ultrasonically dispersing for 20 minutes to obtain aluminum oxide polishing liquid;

[0044] Step 2, adding a modifier to the alumina polishing liquid, and ultrasonically stirring for 4 hours to obtain a modified alumina polishing liquid;

[0045] Step 3, adding an oxidant to the modified alumina polishing liquid and adjusting the pH value to a desired value to obtain an alumina polishing liquid that reaches stability in about 40 hours.

[0046] Polishing performance test: The above-prepared alumina polishing liquid was used to perform a silicon wafer polishing experiment, using a polishing machine with a polishing pressure of 100g / cm 2 , the lower plate speed is 100rpm, the polishing liquid flow rate is 8mL / min, and a precision balance with an accuracy of 0.01mg is used to weigh and calculate the material removal efficiency. After polishing, the surface roughness of the material is tested by ZYGO5022 to measure the surface roughness of the silicon wafer.

[0047] After polishing, the material removal efficiency is R=45nm / min and the surface roughness is Ra=0.23nm.

[0048] Example 2

[0049] This embodiment provides an aluminum oxide polishing liquid: the polishing liquid is composed of aluminum oxide abrasive, oxidant, modifier polyvinyl pyrrolidone, dispersant and pure water, and the mass percentage of each component is as follows:

[0050] Aluminum oxide abrasive 15%;

[0051] Ammonium dichromate 2%;

[0052] Polyvinylpyrrolidone 1%;

[0053] Polyacrylic acid 1%;

[0054] Pure water 81%.

[0055] Specifically prepared by the following method:

[0056] Step 1, adding aluminum oxide abrasive and dispersant under mechanical stirring, and ultrasonically dispersing for 20 minutes to obtain aluminum oxide polishing liquid;

[0057] Step 2, adding a modifier to the alumina polishing liquid, and ultrasonically stirring for 4 hours to obtain a modified alumina polishing liquid;

[0058] Step 3, adding an oxidant to the modified alumina polishing liquid and adjusting the pH value to a desired value to obtain an alumina polishing liquid that reaches stability in about 40 hours.

[0059] Polishing performance test: The above-prepared alumina polishing liquid was used to perform a silicon wafer polishing experiment, using a polishing machine with a polishing pressure of 100g / cm 2 , the lower plate speed is 100rpm, the polishing liquid flow rate is 8mL / min, and a precision balance with an accuracy of 0.01mg is used to weigh and calculate the material removal efficiency. After polishing, the surface roughness of the material is tested by ZYGO5022 to measure the surface roughness of the silicon wafer.

[0060] After polishing, the material removal rate is R=77nm / min and the surface roughness is Ra=0.15nm.

[0061] Control trial 1

[0062] The polishing liquid preparation method and raw material ratio provided in this experiment are the same as those in Example 1, except that the raw materials used in this example do not include the modifier polyvinyl pyrrolidone.

[0063] According to the polishing experiment method provided in Example 1, a polishing experiment was conducted. After polishing, the material removal rate was R=67nm / min, and the surface roughness Ra=0.7nm.

[0064] Control trial 2

[0065] The polishing liquid preparation method and raw material ratio provided in this experiment are the same as those in Example 1, except that the raw materials used in this example do not include the dispersant polyacrylic acid.

[0066] According to the polishing experiment method provided in Example 1, a polishing experiment was conducted. After polishing, the material removal rate was R=63nm / min, and the surface roughness Ra=0.75nm.

[0067] Control trial 3

[0068] The polishing liquid preparation method and raw material ratio provided in this experiment are the same as those in Example 1, except that the amount of polyvinyl pyrrolidone used is 0.05%; the amount of polyacrylic acid used is 0.5%.

[0069] According to the polishing experiment method provided in Example 1, a polishing experiment was conducted. After polishing, the material removal rate was R=53nm / min, and the surface roughness Ra=1.48nm.

[0070] Control experiment 4

[0071] The polishing liquid preparation method and raw material ratio provided in this experiment are the same as those in Example 1, except that the amount of polyvinyl pyrrolidone used is 0.5%; the amount of polyacrylic acid used is 0.05%.

[0072] According to the polishing experiment method provided in Example 1, a polishing experiment was conducted. After polishing, the material removal rate was R=39 nm / min, and the surface roughness was Ra=0.81 nm.

[0073] Control experiment 5

[0074] The polishing liquid preparation method and raw material ratio provided in this experiment are the same as those in Example 1, except that sodium alginate is used to replace polyvinyl pyrrolidone.

[0075] According to the polishing experiment method provided in Example 1, a polishing experiment was conducted. After polishing, the material removal rate was R=31 nm / min, and the surface roughness was Ra=2.33 nm.

[0076] Controlled trial 6

[0077] The polishing liquid preparation method and raw material ratio provided in this experiment are the same as those in Example 1, except that:

[0078] Step 1, adding a modifier to the alumina abrasive, and ultrasonically stirring for 4 hours to obtain a modified alumina polishing liquid;

[0079] Step 2, adding the modified alumina polishing liquid and the dispersant under mechanical stirring, and ultrasonically dispersing for 20 minutes to obtain an alumina polishing liquid;

[0080] Step 3, adding a proper amount of oxidant to the aluminum oxide polishing liquid and adjusting the pH value to a desired value to obtain an aluminum oxide polishing liquid.

[0081] According to the polishing experiment method provided in Example 1, a polishing experiment was conducted. After polishing, the material removal rate was R=37nm / min, and the surface roughness was Ra=1.56nm.

[0082] Dispersibility:

[0083] The method for measuring the dispersibility of the polishing liquid of the present invention is to put the polishing liquid into a thin glass tube with a scale and directly observe the precipitation or stratification degree of the solution in different time periods.

[0084] Average particle size:

[0085] The average hydrated particle size of Al2O3 particles in the polishing liquid is measured by a method that takes advantage of the monochromaticity and strong directionality of laser. The instrument used is a BT-9300S laser particle size distribution analyzer. The suspension is ultrasonically dispersed for 15 minutes before measurement. Figure 2 To add PVP and Figure 1This is the average particle size diagram of alumina without adding PVP (its primary average particle size is 800nm).

[0086] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an aluminum oxide polishing liquid, characterized in that: Alumina abrasive is first dispersed by a dispersant, then modified by a modifier, and finally treated by an oxidant to obtain an alumina polishing liquid; in terms of mass percentage, the alumina polishing liquid comprises: 15% alumina, 2% oxidant, 2% additive, and the rest is deionized water; The modifier is polyvinyl pyrrolidone; Includes steps: Step 1, mixing aluminum oxide abrasive and a dispersant to obtain a mixed material; Step 2, adding polyvinyl pyrrolidone to the mixed material and mixing to obtain a modified mixed material; Step 3, adding an oxidant to the mixed material, adjusting the pH, and obtaining an aluminum oxide polishing liquid; The additive is compounded by a modifier and a dispersant; The mass ratio of the modifier to the dispersant is 1:1; The dispersant is polyacrylic acid.

2. The method for preparing an aluminum oxide polishing liquid according to claim 1, characterized in that: In step 1 and / or step 2, the dispersion and mixing are performed by ultrasonic and / or mechanical stirring.

3. An aluminum oxide polishing liquid, characterized in that: The method for preparing an aluminum oxide polishing liquid according to any one of claims 1 to 2 is adopted, wherein the oxidant includes one or any combination of potassium dichromate, potassium persulfate, ammonium dichromate, and hydrogen peroxide.

4. The aluminum oxide polishing liquid according to claim 3, characterized in that: Calculated by mass percentage, the alumina crystal form is α-type, the average particle size is 0.05μm-5μm, and the specific surface area is ≥5m 2 / g.

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