Method for reversing negatively charged cerium oxide polishing particles and chemical mechanical polishing slurry

Abstract

In the present invention, charge reversal is performed on negatively charged cerium oxide particles by using a method in which a polyquaternium is used in combination with a small-molecule quaternary ammonium compound, so that the polishing rate on a pattern where TEOS and Si are coplanar can be effectively increased and reach 8000 Å / min. The method is applicable to both sol‑gel derived cerium oxide particles and calcined cerium oxide particles.

Description

A method for reversing the negative charge of cerium oxide abrasive particles and a chemical mechanical polishing slurry Technical Field

[0001] This invention relates to a method for reversing the negative charge of cerium oxide abrasive particles and a chemical mechanical polishing slurry, and more particularly to a chemical mechanical polishing composition for planarization of semiconductor materials. Background Technology

[0002] With the continuous development of semiconductor technology, semiconductor manufacturing processes are gradually approaching their physical limits, Moore's Law is slowing down, and advanced packaging has become an important track to surpass Moore's Law. Among these, SoIC (System on Integrated Chips) is a crucial part of 3D packaging, typically involving a coplanar structure of silicon dioxide (TEOS) and silicon (Si). It is desirable that the chemical mechanical polishing slurry used has a high polishing rate for both TEOS and Si, preferably greater than [a certain value]. Furthermore, the ratio of their speeds is close to 1:1.

[0003] Typically, cerium oxide polishing slurries have a significantly higher polishing rate than silicon oxide polishing slurries, making them valuable in CMP applications. Untreated cerium oxide abrasive particles generally carry a positive charge. To reduce the mechanical impact force between the abrasive particles and the polishing surface while simultaneously increasing the polishing rate, the cerium oxide particle surface undergoes secondary charge reversal modification, i.e., surface coating with different polymers. The first charge reversal uses a negatively charged polymer containing carboxyl groups; the second reversal uses a positively charged polymer containing quaternary ammonium cations, i.e., polyquaternary ammonium salts. However, the charge reversal of polyquaternary ammonium salts can suppress the polishing rate of TEOS to some extent. The more polyquaternary ammonium salts are added during reversal, the more pronounced the suppression effect becomes. Therefore, it is difficult to achieve a polishing rate greater than [value missing] on patterned wafers (where TEOS and Si are coplanar). The polishing rate is improved. This invention replaces a portion of the polyquaternary ammonium salt with a small-molecule quaternary ammonium compound, and modifies the surface of negatively charged particles through a combination of polymer and small molecules. This effectively increases the polishing rate of TEOS and Si on the pattern, achieving [the desired polishing rate]. Furthermore, the ratio of their speeds is close to 1:1. Summary of the Invention

[0004] This invention discloses a chemical mechanical polishing fluid, comprising: negatively charged cerium oxide abrasive particles, a polyquaternary ammonium salt, a small molecule quaternary ammonium compound, water, and a pH adjuster.

[0005] Preferably, the polyquaternium salt is polyquaternium salt-37.

[0006] Preferably, the small molecule quaternary ammonium compound is selected from benzyltriethylammonium chloride, butyltrimethylammonium chloride, and tetrabutylammonium hydroxide.

[0007] Preferably, the negatively charged cerium oxide particles are sol-type or calcined cerium oxide.

[0008] Preferably, the content of the negatively charged cerium oxide is 1wt%-2wt%.

[0009] Preferably, the total content of the polyquaternary ammonium salt and the small molecule quaternary ammonium compound is ≥300ppm.

[0010] Preferably, the polyquaternary ammonium salt content is 100-200 ppm.

[0011] Preferably, the content of the small molecule quaternary ammonium compound is 100-300 ppm.

[0012] Preferably, the pH value of the chemical mechanical polishing solution is 9.5–11.5.

[0013] This invention also discloses a method for reversing the negative charge of cerium oxide grinding particles, comprising the following steps:

[0014] S1, mix the sol-type or calcined cerium oxide dispersion stock solution with a carboxyl-containing negatively charged polymer or monomer solution, stir and then place it in an ultrasonic tank for ultrasonic dispersion to obtain a negatively charged cerium oxide dispersion;

[0015] S2, the negatively charged cerium oxide dispersion is mixed with polyquaternary ammonium salt and small molecule quaternary ammonium compound, stirred and then placed in an ultrasonic tank for ultrasonic dispersion, and then the pH value is adjusted with a pH adjuster to obtain a positively charged cerium oxide dispersion.

[0016] Preferably, the carboxyl-containing negatively charged polymer or monomer is ammonium polyacrylate.

[0017] Preferably, in S1, the mass ratio of the carboxyl-containing negatively charged polymer or monomer to the cerium oxide particles is 1:250.

[0018] Preferably, in S2, the concentrations of the negatively charged cerium oxide particles, polyquaternary ammonium salt, and small molecule quaternary ammonium compound are the concentrations disclosed above.

[0019] This invention employs a method combining polyquaternary ammonium salts and small-molecule quaternary ammonium compounds to reverse the charge of negatively charged cerium oxide particles, effectively improving the polishing rate on the TEOS and Si coplanar pattern, achieving... This method is applicable to both sol-type and calcined cerium oxide particles. Attached Figure Description

[0020] Figure 1 is a schematic diagram of the Pattern structure. Detailed Implementation

[0021] The chemical mechanical polishing composition of the present invention will be described in detail below through specific embodiments to provide a better understanding of the present invention, but the following embodiments do not limit the scope of the present invention.

[0022] The particles used in this invention are all negatively charged cerium oxide particles that have undergone one inversion (cerium oxide particle concentration is 10%). The specific method for the first inversion is as follows:

[0023] 5 kg of 20% sol-type or calcined cerium oxide dispersion stock solution was mixed with 10 g of 40% ammonium polyacrylate solution, and the mixture was brought up to 10 kg with deionized water. After stirring for 10 minutes, the mixture was ultrasonically dispersed in an ultrasonic bath for 90 minutes to obtain the first inverted sol-type or calcined negatively charged particles. Subsequently, the particles were further inverted into positively charged particles according to the formulations in the comparative proportions or examples.

[0024] According to the proportions of each component in Table 1, each component was dissolved in deionized water, and the mass percentage was made up to 100% with deionized water. After stirring for 10 minutes, the solution was placed in an ultrasonic bath and ultrasonically dispersed for 90 minutes. Subsequently, the pH was adjusted to 11.0 with KOH to obtain the polishing solutions of the comparative examples and embodiments of the present invention.

[0025] Table 1. Components and content of polishing solutions in comparative and example samples.

[0026] As can be seen, under alkaline pH 11.0 conditions, whether using a polyquaternium-37 or a combination of a small molecule quaternium-37 and polyquaternium-37 to modify cerium oxide particles, the negatively charged particles can be effectively reversed. The resulting polishing solution has a zeta potential greater than 30mV, does not show significant sedimentation, and can exist stably.

[0027] The polishing rate detection method of the chemical mechanical polishing slurry in the comparative examples and embodiments of this invention:

[0028] The patterned wafer was polished using an Ebara polishing machine. The pattern's structural feature was that TEOS and Si were coplanar, as shown in Figure 1. TEOS and Si had different linewidth ratios, such as 90*10µm and 50*50µm. The TEOS film thickness was measured using a NanoSpec film thickness measurement system (NanoSpec6100-300, Shanghai Nanotechnology Co., Ltd.). The Si film thickness was calculated by varying the TEOS film thickness with respect to the step height. We measured the polishing rates at nine sites with different linewidth ratios on the pattern and calculated the average polishing rates of TEOS and Si. The corresponding polishing conditions included: an IC1000 polishing pad, platen and head rotation speeds of 93 rpm and 87 rpm respectively, a polishing pressure of 4.0 psi, a polishing fluid flow rate of 300 mL / min, and a polishing time of 60 s.

[0029] The method for measuring the Zeta potential on the surface of cerium oxide particles is as follows:

[0030] The surface charge of cerium oxide particles was characterized using the zeta potential. The chemimechanical polishing slurry was diluted to a cerium oxide content of 0.2% and then placed in a quartz cuvette. The zeta potential was measured using a Malvern instrument.

[0031] Table 2 Polishing rates of the polishing slurries in the comparative and example cases

[0032] As can be seen from the results in Table 2, when only polyquaternium-37 inversion particles are used, the rates of TEOS and Si on the pattern are only [missing information]. Replacing a portion of polyquaternary ammonium salt-37 with hexamethylammonium bromide (Comparative Example 1B) can increase the polishing rate of TEOS and Si by [percentage missing]. and The above figures show that the ratio of TEOS to Si is not close to 1:1. The CMP technology required for SOIC packaging demands that TEOS and Si be kept as coplanar as possible, with minimal dishing. If the TEOS rate is slower than the Si rate, it will cause TEOS protrusion, hindering subsequent processes. When using dodecyl dimethyl benzyl ammonium chloride in combination with polyquaternium-37 as a modifier (Comparative Example 1C), the polishing rates of TEOS and Si are significantly suppressed. This is likely because the long-chain alkyl groups in the dodecyl dimethyl benzyl chloride molecule adsorb onto the wafer surface, acting as an inhibitor. The results of Examples 1D, 1E, and 1F show that replacing a portion of polyquaternium-37 with benzyl triethyl ammonium chloride, butyl trimethyl ammonium chloride, and tetrabutyl ammonium hydroxide can significantly improve the polishing rates of TEOS and Si on the pattern, achieving... The above, and the ratio of the two is close to 1:1.

[0033] According to the proportions of each component in Table 3, each component was dissolved in deionized water, and the mass percentage was made up to 100% with deionized water. After stirring for 10 minutes, the solution was placed in an ultrasonic bath for ultrasonic dispersion for 90 minutes. Subsequently, the pH was adjusted to 11.0 with KOH to obtain the polishing solutions of the comparative examples and embodiments of the present invention.

[0034] Table 3. Effects of adding different amounts of benzyltriethylammonium chloride on polishing effect.

[0035] Comparative Examples 2A, 2B, and 2C show that when the total content of polyquaternium-37 and the small-molecule quaternary ammonium compound benzyltriethylammonium chloride is below 300 ppm, the Zeta potential of the polishing solution is <30 mV, cerium oxide particles are prone to agglomeration and sedimentation, and the polishing solution is unstable. Therefore, in order to effectively reverse the negative charge of cerium oxide particles and stabilize the polishing solution, the total content of polyquaternium-37 and the small-molecule quaternary ammonium compound must be greater than 300 ppm. In Comparative Example 2N, when the content of polyquaternium-37 is 50 ppm, the polishing solution is also unstable, and the particles will settle significantly. Therefore, the content of polyquaternium-37 must also be greater than 50 ppm.

[0036] We conducted polishing tests using a stable polishing slurry. Comparing the polishing results of Comparative Examples 2D and 2E with Examples 2F-2J and 2L and 2M in Table 4, we found that when the content of polyquaternium-37 was 250 ppm, the rate of TEOS reacting with Si was low and could not achieve a reaction rate greater than [missing value]. The polishing rate was [missing information]. However, when the content of polyquaternium-37 was 50 ppm, the polishing slurry was unstable, and the particles experienced significant sedimentation. Therefore, the preferred content range of polyquaternium-37 is 100-200 ppm. When the content of polyquaternium-37 is within this range, the polishing results of Examples 2F-2J and Examples 2L and 2M show that when the content of benzyltriethylammonium chloride is 100-300 ppm, the polishing rates of TEOS and Si on the pattern can reach [missing information]. The above conditions were met, and the ratio of the two components was close to 1:1. If the content of benzyltriethylammonium chloride was further increased to 350 ppm (comparative example 2K), the polishing slurry remained stable, but the polishing rates of TEOS and Si decreased, falling below [a certain value]. Furthermore, simply increasing the content of benzyltriethylammonium chloride without a significant increase in polishing rate will reduce the commercial value of the polishing solution. In summary, the preferred content range for polyquaternary ammonium salts is 100-200 ppm, and when the polyquaternary ammonium salt content is within this range, the preferred content range for small molecule quaternary ammonium compounds is 100-300 ppm.

[0037] Table 4 Polishing rates of the polishing slurries in the comparative examples and embodiments

[0038] According to the proportions of each component in Table 5, each component was dissolved in deionized water, and the mass percentage was made up to 100% with deionized water. After stirring for 10 minutes, the solution was placed in an ultrasonic bath and ultrasonically dispersed for 90 minutes. Subsequently, the pH was adjusted to 11.0 with KOH to obtain the polishing solutions of the comparative examples and embodiments of the present invention.

[0039] Table 5. Effect of sol-type cerium oxide particle concentration on polishing effect

[0040] As can be seen, when the content of sol-type cerium oxide is 0.5%, the rates of TEOS and Si are only... Around [amount missing]. When the content of sol-type cerium oxide gradually increases from 1% to 2%, the polishing rate of both TEOS and Si on the pattern can reach [amount missing]. The above ratio is approximately 1:1. If the cerium oxide content is further increased to 2.5%, the TEOS and Si rates will decrease to... Below (Comparative Example 3F). Therefore, in summary, the content of cerium oxide particles is preferably 1%-2%.

[0041] According to the proportions of each component in Table 6, each component was dissolved in deionized water, and the mass percentage was made up to 100% with deionized water. After stirring for 10 minutes, the solution was placed in an ultrasonic bath for ultrasonic dispersion for 90 minutes. Subsequently, the pH value was adjusted with KOH to obtain the polishing solutions of the comparative examples and embodiments of the present invention.

[0042] Table 6 Polishing effect of polishing slurry for calcined cerium oxide particles

[0043] A comparison of Comparative Example 4A and Example 4E shows that the method of using polyquaternium-37 in combination with benzyltriethylammonium chloride to reverse particle formation is also applicable to calcined cerium oxide particles. In Comparative Example 4A, which only added polyquaternium-37, the polishing rates of TEOS and Si were only [missing data]. Around 100%, while after replacing part of the polyquaternary ammonium salt-37 with benzyltriethylammonium chloride, the polishing rate of TEOS and Si can reach 100%. The above ratio is close to 1:1, meeting the technical requirements. The polishing results of Examples 4B-4E and Comparative Example 4F show that at pH 9.5-11.5, both TEOS and Si on the pattern can achieve [the desired results]. The polishing rates mentioned above. However, when the pH drops to 9.0, the rates of TEOS and Si decrease significantly, only reaching [amount missing]. If the pH of the polishing slurry is further increased to 12.0, the stability of the slurry will decrease, and particles will easily settle. Therefore, a pH range of 9.5-11.5 is preferred.

[0044] This invention employs a method combining polyquaternary ammonium salts with small-molecule quaternary ammonium compounds (including but not limited to benzyltriethylammonium chloride, butyltrimethylammonium chloride, and tetrabutylammonium hydroxide) to reverse the charge of negatively charged cerium oxide particles. This effectively improves the polishing rate on the coplanar pattern of TEOS and Si, achieving... This method is applicable to both sol-gel and calcined cerium oxide particles. The total content of polyquaternary ammonium salt and small molecule quaternary ammonium compounds needs to be greater than 300 ppm to obtain a stable polishing solution. The preferred content range of polyquaternary ammonium salt is 100-200 ppm. When the content of polyquaternary ammonium salt is within this range, taking benzyltriethylammonium chloride as an example, the preferred addition amount is 100-300 ppm. The concentration of cerium oxide particles in the polishing solution is preferably 1%-2%, and the pH of the polishing solution is preferably 9.5-11.5.

[0045] All concentrations mentioned in this invention refer to mass percentage concentrations.

[0046] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A chemical mechanical polishing slurry, characterized in that, include: Negatively charged cerium oxide abrasive particles, polyquaternary ammonium salts, small molecule quaternary ammonium compounds, water, and pH adjusters.

2. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The polyquaternium salt is polyquaternium salt-37.

3. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The small molecule quaternary ammonium compound is selected from benzyltriethylammonium chloride, butyltrimethylammonium chloride, and tetrabutylammonium hydroxide.

4. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The content of the negatively charged cerium oxide particles is 1wt%-2wt%.

5. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The total content of the polyquaternary ammonium salt and small molecule quaternary ammonium compounds is ≥300ppm.

6. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The content of the polyquaternary ammonium salt is 100-200 ppm.

7. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The content of the small molecule quaternary ammonium compound is 100-300 ppm.

8. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The pH value is 9.5 to 11.

5.

9. A method for reversing the negative charge of cerium oxide grinding particles, characterized in that, Includes the following steps: S1, mix the sol-type or calcined cerium oxide dispersion stock solution with a carboxyl-containing negatively charged polymer or monomer solution, stir and then place it in an ultrasonic tank for ultrasonic dispersion to obtain a negatively charged cerium oxide dispersion; S2, the negatively charged cerium oxide dispersion is mixed with polyquaternary ammonium salt and small molecule quaternary ammonium compound, stirred and then placed in an ultrasonic tank for ultrasonic dispersion, and then the pH value is adjusted with a pH adjuster to obtain a positively charged cerium oxide dispersion.

10. The method as described in claim 9, characterized in that, The negatively charged polymer or monomer containing carboxyl groups is ammonium polyacrylate.

11. The method as described in claim 9, characterized in that, In S1, the mass ratio of the carboxyl-containing negatively charged polymer or monomer to the cerium oxide particles is 1:

250.

12. The method as described in claim 9, characterized in that, In S2, the concentrations of the negatively charged cerium oxide particles, polyquaternary ammonium salts, and small molecule quaternary ammonium compounds are as described in any one of claims 4-7.

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