Modified silicon dioxide abrasive, preparation method thereof and polishing solution prepared from modified silicon dioxide abrasive

Abstract

The preparation method of the modified silicon dioxide grinding material comprises the following steps that under the dark condition and the nitrogen atmosphere, a silane coupling agent, a modifier, a photoinitiator and silica sol are mixed, then stirring reaction is conducted under illumination, after the reaction is finished, separation is conducted, and the modified silicon dioxide grinding material is obtained. Preparing a modified silicon dioxide abrasive material; and mixing with a polishing rate accelerator and a pH regulator to prepare the polishing solution. The preparation process is simple and easy to implement, the effect is excellent, and good surface quality can be obtained under the condition that the polishing rate of the silicon wafer is increased.

Description

Technical Field

[0001] This invention relates to the field of semiconductor processing technology, and in particular to a modified silicon dioxide abrasive, its preparation method, and the polishing slurry prepared therefrom. Background Technology

[0002] In recent years, with the development of integrated circuit technology in my country, the semiconductor field has increasingly higher requirements for silicon wafer surface quality and polishing rate. Chemical mechanical polishing (CMP) is an important method for global planarization of silicon wafer surfaces. Silicon wafer polishing is divided into rough polishing and fine polishing. Fine polishing, as the final step in the polishing process, is crucial to the surface quality of the finished silicon wafers. The surface of a finely polished silicon wafer should be free of polishing marks, scratches, chemical corrosion, and have a low surface roughness. Polishing slurry formulations typically consist of abrasive particles, oxidants, complexing agents, and dispersants. Commonly used abrasive particles include nano-silica and nano-cerium dioxide. Choosing a suitable polishing slurry can simultaneously improve polishing rate and surface roughness, achieving better production results.

[0003] To address these issues, the abrasive in the polishing slurry can be modified. Common modification methods include modifying the abrasive particles by coating hard silica particles with elastic organic matter to form a core-shell structure. The elastic deformation of the surface organic layer reduces hard damage to the silicon wafer and lowers surface roughness during polishing. However, this method cannot significantly improve the polishing rate. Adding alkaline rate accelerators such as potassium carbonate to the polishing slurry formulation softens the silicon wafer surface through an alkaline environment, which can improve the polishing rate. However, this method may introduce metal ions, increasing post-processing costs and failing to achieve satisfactory surface quality.

[0004] With the continuous development of my country's semiconductor industry and the advancement of integrated circuit products, my country is encountering more and more problems in chip manufacturing. Among these, the development of high-quality silicon wafer polishing slurries is an urgent issue. Currently, my country has a large market for polishing slurries, but high-end products still rely on imports. Therefore, researching polishing slurries with excellent performance is an urgent problem to be solved, and further improvements to polishing compositions are needed. Summary of the Invention

[0005] To address the problems of low polishing rates and poor surface quality in existing abrasive technologies, this invention provides a modified silica abrasive, its preparation method, and the polishing slurry prepared therefrom. This invention uses silica abrasive prepared with a silane coupling agent and a modifier, which is then formulated into a polishing slurry. The preparation process of this invention is simple and easy to implement, yielding excellent results and achieving good surface quality while increasing the polishing rate of silicon wafers.

[0006] The surface of silica contains hydroxyl groups generated by hydrolysis. One end of the silane coupling agent contains silanoxy groups, which can be grafted onto the surface of silica particles under hydrolysis conditions. The other end of the silane coupling agent contains different functional groups, which allows for the selective design of silane coupling agents to obtain modified silica abrasives with different properties.

[0007] Silicon wafers also contain silanol groups on their surface when hydrolyzed. They carry a negative charge in the polishing environment, so the mechanical force during the polishing process can be enhanced by the electrostatic attraction between the positive and negative charges, thereby increasing the polishing rate. Amino-containing modifiers can hydrolyze their amino groups into ammonium ions in water, and can also generate the alkaline environment required for polishing, making them an ideal choice.

[0008] The technical solution of the present invention is as follows: The first objective of this invention is to provide a method for preparing modified silica abrasive, comprising the following steps: In the dark and under a nitrogen atmosphere, a silane coupling agent, a modifier, a photoinitiator, and a silica sol were mixed and then stirred under light. After the reaction was completed, the mixture was separated to obtain modified silica abrasive.

[0009] In one embodiment of the present invention, the silica sol has a particle size of 100 nm and a solid content of 20-40%.

[0010] In one embodiment of the present invention, the silane coupling agent is γ-mercaptopropyltrimethoxysilane (KH590) or 3-mercaptopropyltriethoxysilane (KH580); the amount of silane coupling agent used is 1-3% of the mass of silica in the silica sol.

[0011] Preferably, the silane coupling agent is γ-mercaptopropyltrimethoxysilane (KH590).

[0012] Preferably, the amount of silane coupling agent used is 2% of the mass of silica in the silica sol.

[0013] In one embodiment of the present invention, the modifier is one or more of acrylamide, dimethylaminoethyl acrylate, and dimethylaminoethyl methacrylate; the amount of modifier used is 1-20% of the mass of silica in the silica sol.

[0014] Preferably, the modifier is acrylamide.

[0015] In one embodiment of the present invention, the photoinitiator is one or more of benzophenone, 4-methylbenzophenone, and dialkoxyacetophenone; the amount used is 1-10% of the mass of silica in the silica sol.

[0016] In one embodiment of the present invention, the illumination conditions are: ultraviolet light with a wavelength of 365 nm for 10-20 min, and a light intensity of 10 mW / cm². 2 .

[0017] In one embodiment of the present invention, the method for preparing modified silica abrasive includes the following steps: The silane coupling agent was added to a flask containing silica sol and stirred at 50°C for 30 min. Then, a modifier and a photoinitiator were added. The reaction was carried out in darkness under a nitrogen atmosphere at a wavelength of 365 nm and a light intensity of 10 mW / cm². 2 The reaction was carried out under ultraviolet light for 10 min, and then the prepared liquid was centrifuged. The resulting lower solid was dried and washed with ethanol and water. This process was repeated three times to obtain modified silica abrasive.

[0018] A second objective of this invention is to provide a modified silica abrasive prepared by the above-described preparation method.

[0019] A third objective of this invention is to provide a polishing fluid containing the above-mentioned modified silica abrasive, comprising the modified silica abrasive, a polishing rate promoter, and a pH adjuster.

[0020] In one embodiment of the present invention, the polishing rate accelerator is a hydroxide or an ammonium salt; the amount of polishing rate accelerator is 1-5% of the mass of the modified silica abrasive.

[0021] Preferably, the polishing rate accelerator is tetramethylammonium hydroxide.

[0022] In one embodiment of the present invention, the pH adjuster is an acid or a base; the acid is an organic acid or an inorganic acid; the base is an organic amine, a quaternary ammonium salt, or a metal hydroxide; the pH adjuster adjusts the pH of the polishing solution to 7-11.

[0023] Preferably, the acid is acetic acid and the base is triethylamine.

[0024] Preferably, the pH of the polishing solution is adjusted to 8-10 by a pH adjuster.

[0025] In one embodiment of the present invention, the polishing solution further includes deionized water.

[0026] In one embodiment of the present invention, the polishing slurry comprises: 40-60% modified silica abrasive, 1-5% of the mass of the modified silica abrasive as a polishing rate promoter, and pH adjuster used to make the pH of the polishing slurry 7-11, with the remainder being water.

[0027] In one embodiment of the present invention, a polishing slurry containing modified silica abrasive is prepared by: The silane coupling agent was added to a flask containing silica sol and stirred at 50°C for 30 min. Then, a modifier and photoinitiator were added, and the reaction was carried out in the dark under a nitrogen atmosphere with ultraviolet light at a wavelength of 365 nm and an intensity of 10 mW / cm² for 10 min. The prepared liquid was then centrifuged, and the resulting lower solid was dried and washed with ethanol and water, repeated three times. The resulting solid was then ground and ultrasonically dispersed in deionized water. Finally, appropriate polishing rate accelerators and pH adjusters were added to prepare the polishing solution.

[0028] The beneficial technical effects of this invention are as follows: This invention modifies silica abrasives with silane coupling agents and amino modifiers, and uses them to formulate polishing slurries, resulting in polishing slurry formulations with good polishing effects. The preparation process is simple and the post-processing is convenient, showing great promise. Attached Figure Description

[0029] Figure 1 This is a comparison of the infrared spectra of modified silica abrasive and unmodified silica abrasive in Example 4.

[0030] Figure 2 The polishing rates of the polishing fluids prepared in Examples 1-4 and Comparative Example 1 are shown.

[0031] Figure 3 The polishing rate of the polishing fluid prepared in Examples 5-11 is shown.

[0032] Figure 4 The polishing solution prepared in Examples 1-4 and Comparative Example 1 was used to polish the surface roughness of the silicon wafer.

[0033] Figure 5 The surface roughness of the silicon wafer was polished using the polishing slurry prepared in Examples 5-11.

[0034] Figure 6 The image shows a TEM (Scanning Electron Microscope) image of the modified silica abrasive prepared for Comparative Example 1.

[0035] Figure 7 This is a TEM scanning electron microscope image of the silica abrasive prepared in Example 2.

[0036] Figure 8 This is an AFM morphology height diagram of the silicon wafer surface polished by the polishing slurry prepared in Example 3.

[0037] Figure 9 AFM morphology height map of the silicon wafer surface polished by the polishing slurry was prepared for Comparative Example 1. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] The raw materials and reagents used in this invention are all commercially available.

[0040] Evaluation of polishing and grinding effects: Polishing experiments were conducted on silicon wafers using polishing slurry. The chemical mechanical polishing (CMP) experiment used a Universal 300B polishing machine manufactured by Tianjin Huahai Qingke Co., Ltd., an IC1010 polishing pad manufactured by Dow Chemical Company, and an A165P dresser manufactured by 3M Company. The polishing pressure was 2 psi, the polishing head / disc speed was 87 / 93, the polishing time was 3 min, and the flow rate was 200 ml / min.

[0041] Example 1 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: 0.7 g of KH590 was added to 125 g of silica sol (40% solid content, 100 nm particle size), and the mixture was stirred at 50 °C for 3 h. Then, 0.7 g of acrylamide (AM) and 0.7 g of benzophenone were added, and the mixture was reacted under 365 nm light source for 10 min. The resulting solution was centrifuged, the lower precipitate was dried, and washed three times with ethanol and water to obtain modified silica abrasive. The modified silica abrasive was ground and ultrasonically dispersed in deionized water to obtain S-1, with a modified silica abrasive content of 40%. A rate accelerator TMAH of 5% relative to the mass of the modified silica abrasive was added, and the pH was adjusted to 11 using acetic acid / triethylamine to obtain KH590-PAM-1 polishing fluid.

[0042] Example 2 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: 0.7 g of KH590 was added to 125 g of silica sol (40% solid content, 100 nm particle size), and the mixture was stirred at 50 °C for 3 h. Then, 1.4 g of acrylamide (AM) and 0.7 g of benzophenone were added, and the mixture was reacted under 365 nm light source for 10 min. The resulting solution was centrifuged, the lower precipitate was dried, and washed three times with ethanol and water to modify the silica abrasive. The obtained modified silica abrasive was ground and ultrasonically dispersed in deionized water to prepare S-2, with a modified silica abrasive content of 50%. A rate accelerator TMAH of 5% (relative to the mass of the modified silica abrasive) was added, and the pH was adjusted to 11 using acetic acid / triethylamine to obtain KH590-PAM-2 polishing slurry. Figure 6 , Figure 7 It can be seen that compared with the unmodified abrasive, the modified abrasive exhibits a core-shell structure, proving that the modification was successful.

[0043] Example 3 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: 0.7 g of KH590 was added to 125 g of silica sol (40% solid content, 100 nm particle size), and the mixture was stirred at 50 °C for 3 h. Then, 2.8 g of acrylamide (AM) and 0.7 g of benzophenone were added, and the mixture was reacted under 365 nm light source for 10 min. The resulting solution was centrifuged, the lower precipitate was dried, and washed three times with ethanol and water to modify the silica abrasive. The obtained modified silica abrasive was ground and ultrasonically dispersed in deionized water to prepare S-3, with a modified silica abrasive content of 40%. A rate accelerator TMAH of 5% (relative to the mass of the modified silica abrasive) was added, and the pH was adjusted to 11 using acetic acid / triethylamine to obtain KH590-PAM-3 polishing slurry. Figure 8 , Figure 9 It can be seen that the silicon wafer surface is smoother after polishing with modified abrasive, indicating that the silicon wafer surface is better after polishing with the polishing slurry prepared with modified abrasive.

[0044] Example 4 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: 0.7 g of KH590 was added to 125 g of silica sol (40% solid content, 100 nm particle size), and the mixture was stirred at 50 °C for 3 h. Then, 5.6 g of acrylamide (AM) and 0.7 g of benzophenone were added, and the mixture was reacted under 365 nm light source for 10 min. The resulting solution was centrifuged, the lower precipitate was dried, and washed three times with ethanol and water to modify the silica abrasive. The obtained modified silica abrasive was ground and ultrasonically dispersed in deionized water to obtain S-4, with a modified silica abrasive content of 60%. A rate accelerator TMAH of 5% relative to the mass of the modified silica abrasive was added, and the pH was adjusted to 11 using acetic acid / triethylamine to obtain KH590-PAM-4 polishing slurry.

[0045] Infrared characterization was performed, and the results are as follows: Figure 1 As shown, 1070cm -1 A tensile vibration peak of Si-OC appears at 1660 cm⁻¹. -1 A stretching vibration peak of the amide C=O group appears at 2570 cm⁻¹. -1 The thiol stretching vibration peak disappears at 3290 cm⁻¹. -1 The appearance of the stretching vibration peak of the amino group NH indicates that the functional groups of the coupling agent and the modifier have been successfully grafted onto the surface of nano-SiO2.

[0046] Example 5 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: Using S-3 prepared in Example 3, 1% (by weight of the modified silica abrasive) of rate accelerator TMAH was added, and the pH was adjusted to 11 using acetic acid / triethylamine to obtain KH590-PAM-5 polishing slurry.

[0047] Example 6 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: Using S-3 prepared in Example 3, 2% (by weight of the modified silica abrasive) of rate accelerator TMAH was added, and the pH was adjusted to 11 using acetic acid / triethylamine to obtain KH590-PAM-6 polishing slurry.

[0048] Example 7 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: Using S-3 prepared in Example 3, 3% (by weight of the modified silica abrasive) of rate accelerator TMAH was added, and the pH was adjusted to 11 using acetic acid / triethylamine to obtain KH590-PAM-7 polishing slurry.

[0049] Example 8 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: Using S-3 prepared in Example 3, 4% (by weight of the modified silica abrasive) of rate accelerator TMAH was added, and the pH was adjusted to 11 using acetic acid / triethylamine to obtain KH590-PAM-8 polishing slurry.

[0050] Example 9 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: Using S-3 prepared in Example 3, 5% (by weight of the modified silica abrasive) of rate accelerator TMAH was added, and the pH was adjusted to 8 using acetic acid / triethylamine to obtain KH590-PAM-9 polishing slurry.

[0051] Example 10 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: Using S-3 prepared in Example 3, 5% (by weight of the modified silica abrasive) of rate accelerator TMAH was added, and the pH was adjusted to 9 using acetic acid / triethylamine to obtain KH590-PAM-10 polishing slurry.

[0052] Example 11 A method for preparing a silane coupling agent modified silica abrasive polishing slurry includes the following steps: Using S-3 prepared in Example 3, 5% (by weight of the modified silica abrasive) of rate accelerator TMAH was added, and the pH was adjusted to 10 using acetic acid / triethylamine to obtain KH590-PAM-11 polishing slurry.

[0053] Comparative Example 1 The silica sol was centrifuged, dried, and then ultrasonically dispersed in deionized water. Subsequently, 5% TMAH was added and the pH was adjusted to 11 to obtain SY-12 polishing solution.

[0054] Test case (1) Polishing rate Polishing rate is an important indicator of the polishing slurry's ability to remove impurities from the silicon wafer surface. In the aforementioned polishing experiment, the silicon wafer thickness before and after polishing was measured using an optical interferometry film thickness measuring device. The difference between these thicknesses was divided by the polishing time to obtain the polishing rate, which was then used for evaluation. The polishing rates of the polishing slurries prepared in Examples 1-11 and Comparative Example 1 were tested, and the results are shown in Table 1 below. It can be seen that the polishing rate first increases and then decreases with increasing graft content, increases with increasing polishing rate accelerator dosage, and is not significantly affected by pH value.

[0055] The polishing rates of the polishing slurries prepared in Examples 1-4 and Comparative Example 1 are as follows: Figure 2 As shown, the polishing rate of the polishing slurry prepared in Examples 5-11 is as follows: Figure 3 As shown.

[0056] (2) Surface roughness Surface roughness is an important indicator of the surface quality of polished silicon wafers. Lower surface roughness represents a smoother surface, indicating a better polishing effect. Surface roughness was measured in a 5 μm x 5 μm area on the surface of the polished silicon wafer using an atomic force microscope. The surface roughness of silicon wafers polished with the polishing solutions prepared in Examples 1-11 and Comparative Example 1 was tested, and the results are shown in Table 1 below. It can be seen that surface roughness increases with increasing graft content, increasing polishing rate accelerator dosage, and increasing pH value.

[0057] The surface roughness of the silicon wafers polished with the polishing slurry prepared in Examples 1-4 and Comparative Example 1 is as follows: Figure 4 As shown, the surface roughness of the silicon wafer polished by the polishing slurry prepared in Examples 5-11 is as follows: Figure 5 As shown.

[0058] Table 1

[0059] As can be seen from the polishing rate and surface roughness in Table 1 above, the polishing slurry prepared with silica abrasive modified with silane coupling agent has a promoting effect on the polishing effect, achieving a higher polishing speed and better surface quality. Moreover, the abrasive preparation is simple and efficient, which is very much in line with the development trend of polishing slurry in my country and has a very broad application prospect.

[0060] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing modified silica abrasive, characterized in that, Includes the following steps: In the dark and under a nitrogen atmosphere, a silane coupling agent, a modifier, a photoinitiator, and a silica sol were mixed and then stirred under light. After the reaction was completed, the mixture was separated to obtain modified silica abrasive.

2. The preparation method according to claim 1, characterized in that, The particle size of the silica sol is 50-150 nm, and the solid content is 20-40%.

3. The preparation method according to claim 1, characterized in that, The silane coupling agent is γ-mercaptopropyltrimethoxysilane or 3-mercaptopropyltriethoxysilane; the amount of silane coupling agent used is 1-3% of the mass of silica in the silica sol.

4. The preparation method according to claim 1, characterized in that, The modifier is one or more of acrylamide, dimethylaminoethyl acrylate, and dimethylaminoethyl methacrylate; the amount of modifier used is 1-20% of the mass of silica in the silica sol.

5. The preparation method according to claim 1, characterized in that, The photoinitiator is one or more of benzophenone, 4-methylbenzophenone, and dialkoxyacetophenone; the amount used is 1-10% of the mass of silica in the silica sol.

6. The preparation method according to claim 1, characterized in that, The illumination conditions were: ultraviolet light with a wavelength of 365 nm for 10-20 minutes, with a light intensity of 10 mW / cm². 2 .

7. A modified silica abrasive prepared by the preparation method according to any one of claims 1-6.

8. A polishing slurry containing the modified silica abrasive of claim 7, characterized in that, It includes the modified silica abrasive, polishing rate accelerator, and pH adjuster.

9. The polishing slurry according to claim 8, characterized in that, The polishing rate accelerator is a hydroxide or ammonium salt; the amount of polishing rate accelerator is 1-5% of the mass of the modified silica abrasive.

10. The polishing slurry according to claim 8, characterized in that, The pH adjuster is an acid or a base; the acid is an organic acid or an inorganic acid; the base is an organic amine, a quaternary ammonium salt, or a metal hydroxide; the pH adjuster adjusts the pH of the polishing solution to 7-11.

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