High stability sticmp polishing solution with removal rate selection ratio adjustable

Abstract

The application discloses a high-stability STI CMP polishing solution with adjustable removal rate selection ratio, which is used in STI CMP under an acidic condition with pH=2-6 and comprises the following components in percentage by mass: CeO2 abrasive: 0.1wt%-5wt%; amino acid: 0.1wt%-4wt%; polyhydric alcohol: 0.5wt%-6wt%; polyvinyl alcohol: 0.01wt%-1wt%; pH regulator; and the rest is deionized water; the polyvinyl alcohol has a molecular weight of 10,000-100,000; the amino acid is one or more of glycine, alanine, aspartic acid, glutamic acid, arginine, proline, picolinic acid, nicotinic acid or derivatives thereof; and the polyhydric alcohol is one or more of D-sorbitol, mannitol, lactitol, maltitol, maltotriitol, xylitol, dulcitol or derivatives thereof. On the basis of high removal rate selection ratio, the polishing solution can ensure the stability of the polishing rate within 112 months.

Description

Technical Field

[0001] This invention relates to the field of shallow trench isolation (STI) chemical mechanical polishing (CMP) technology, specifically to a highly stable STI CMP polishing slurry with adjustable removal rate selectivity, wherein the polishing slurry maintains a relatively stable polishing rate over a 12-month period. Background Technology

[0002] Shallow trench isolation (STI) is a crucial method for isolating active devices in current IC manufacturing. It involves creating trenches on the Si substrate surrounding the active components and filling them with an insulating dielectric. As the trenches are filled, excess TEOS (thermal eosinophilic oxide) is deposited in unwanted areas across the entire wafer. Excess TEOS must be completely removed using chemical mechanical polishing (CMP). The Si3N4 stop layer is a critical part of this process; Si3N4 prevents damage to the underlying epitaxial growth surface during CMP.

[0003] STI CMP places high demands on the selectivity of TEOS and Si3N4 removal rates, requiring a high TEOS removal rate while effectively suppressing the Si3N4 removal rate. The aim is to quickly remove excess TEOS while ensuring good protection of the trench oxides. CeO2 abrasive is relatively soft and reacts chemically with SiO2 to form "chemical teeth," and it is not effective at removing the harder Si3N4. Therefore, STI CMP polishing slurries mostly use CeO2 abrasive.

[0004] The industry has conducted in-depth research on the removal rate selectivity of STI polishing slurries, and most researchers have made effective research results on the high removal rate selectivity of TEOS / Si3N4. Patent CN111378372B uses CeO2 abrasive and, under pH=4.5-4.8 conditions, adds a certain concentration of acetic acid to achieve a high silica polishing rate and a high silica / silicon nitride polishing rate selectivity. After polishing, the removal rate selectivity of TEOS and Si3N4 is 979-3. However, the selectivity range studied in this patent is too large, and no research has been done on the stability of the removal rate.

[0005] Most current patents focus on the high removal rate selectivity, low oxide loss, and shallow pits of TEOS and Si3N4. There are few reports on the adjustability of the removal rate selectivity of TEOS and Si3N4 within a certain range and the stability of the removal rate of TEOS and Si3N4. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a highly stable STI CMP polishing slurry with an adjustable removal rate selectivity ratio. This slurry, used in STI CMP, has a high removal rate selectivity ratio, with the TEOS / Si3N4 removal rate selectivity ratio adjustable within the range of 30-80. Based on this high removal rate selectivity ratio, the polishing slurry can maintain a stable polishing rate for up to 112 months.

[0007] This invention relates to a highly stable STI chemical mechanical polishing slurry with adjustable removal rate selectivity, used for STI CMP under acidic conditions (pH = 2-6). It mainly comprises CeO2 abrasive, amino acids, polyols, polyvinyl alcohol, pH adjuster, and deionized water.

[0008] The components, measured by mass percentage, are as follows: CeO2 abrasive: 0.1wt%-5wt%; amino acids: 0.1wt%-4wt%; polyols: 0.5wt%-6wt%; polyvinyl alcohol: 0.01wt%-1wt%; pH adjuster; balance is deionized water.

[0009] The amino acids are: one or more of glycine, alanine, aspartic acid, glutamic acid, arginine, proline, pyridinecarboxylic acid, nicotinic acid, or their derivatives.

[0010] The polyols are: D-sorbitol, mannitol, lactitol, maltitol, maltotriol, xylitol, euonymol, or one or more of their derivatives.

[0011] The molecular weight of the polyvinyl alcohol is 10,000 to 100,000, preferably 10,000 to 70,000, including at least one of polyvinyl alcohol 10,000, polyvinyl alcohol 20,000, polyvinyl alcohol 27,000, polyvinyl alcohol 67,000, polyvinyl alcohol 89,000 or other polyvinyl alcohols with different molecular weights.

[0012] The abrasive particle size in the CeO2 abrasive is 60-300 nm, preferably 80-200 nm;

[0013] The pH adjuster includes, but is not limited to: inorganic or organic acids including one or more of nitric acid, phosphoric acid, citric acid, oxalic acid, and acetic acid; and inorganic or organic bases including one or more of potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ethanolamine, and diethanolamine.

[0014] The conditions for polishing TEOS / Si3N4 using polishing slurry are:

[0015] Polishing machine: Universal-150B; Polishing head / disc speed: 87 / 93 rpm; Pressure: 2.8 psi / 3 psi; Flow rate: 150 ml / min; Polishing time: 60 s; Before polishing, stir the prepared polishing solution for 40 min using a high-speed mixer (3500 r / min).

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] The amino acids involved in this invention have different effects on the removal of TEOS, either inhibiting the removal rate of TEOS or having no inhibitory effect, and also inhibiting the removal rate of Si3N4. The polyols involved maintain a certain form of existence in an acidic environment, inhibiting the removal rate of Si3N4 while ensuring that the removal rate of TEOS is not affected. The synergistic effect of amino acids and polyols can achieve an adjustable TEOS / Si3N4 removal rate selectivity ratio within the range of 30-80 within a given dosage range. Combined with polyvinyl alcohol to synergistically disperse CeO2 polishing slurry, the polishing slurry can maintain a stable polishing rate for 12 months. Attached Figure Description

[0018] Figure 1 The diagram shows the changes in the removal rates of TEOS and Si3N4 over the number of months in Example 1; where (a) is the graph showing the change in the removal rate of TEOS over the number of months, and (b) is the graph showing the change in the removal rate of Si3N4 over the number of months.

[0019] Figure 2 The diagram shows the variation of TEOS and Si3N4 removal rates over the number of months in Comparative Example 1; where (a) is the variation of TEOS removal rate over the number of months, and (b) is the variation of Si3N4 removal rate over the number of months.

[0020] Figure 3 The diagram shows the changes in the removal rates of TEOS and Si3N4 over the number of months in Example 2; where (a) is the graph showing the change in the removal rate of TEOS over the number of months, and (b) is the graph showing the change in the removal rate of Si3N4 over the number of months.

[0021] Figure 4 The diagram shows the changes in the removal rates of TEOS and Si3N4 over the number of months in Comparative Example 2; where (a) is the diagram showing the change in the removal rate of TEOS over the number of months, and (b) is the diagram showing the change in the removal rate of Si3N4 over the number of months.

[0022] Figure 5 The diagram shows the changes in the removal rates of TEOS and Si3N4 over the number of months in Example 3; where (a) is the graph showing the change in the removal rate of TEOS over the number of months, and (b) is the graph showing the change in the removal rate of Si3N4 over the number of months.

[0023] Figure 6 The diagram shows the changes in the removal rates of TEOS and Si3N4 over the number of months in Comparative Example 3; where (a) is the diagram showing the change in the removal rate of TEOS over the number of months, and (b) is the diagram showing the change in the removal rate of Si3N4 over the number of months.

[0024] Figure 7 The diagram shows the effect of Example 4 on the removal rate of TEOS and Si3N4 over the number of months; where (a) is the graph of TEOS removal rate over the number of months and (b) is the graph of Si3N4 removal rate over the number of months.

[0025] Figure 8 The diagram shows the effect of different molecular weight polyvinyl alcohols on the TEOS removal rate as a function of months.

[0026] Figure 9 The diagram shows the effect of different molecular weight polyvinyl alcohols on the Si3N4 removal rate as a function of months. Detailed Implementation

[0027] The present invention will be further explained below with reference to the embodiments and accompanying drawings, but this is not intended to limit the scope of protection of this application.

[0028] This invention incorporates amino acids, polyols, and polyvinyl alcohol into the polishing slurry. Under acidic conditions, the protonated amino groups of the amino acids form hydrogen bonds with the surfaces of TEOS and Si3N4, leading to surface adsorption and film formation. While some amino acids may inhibit the removal rate of TEOS, they will definitely inhibit the removal rate of Si3N4. The polyols, through the formation of hydrogen bonds with the surfaces of TEOS and Si3N4 via protonated hydroxyl groups under acidic conditions, also adsorb and form films on the surfaces, but this does not affect the removal rate of TEOS, although it inhibits the removal rate of Si3N4. Adjusting the ratio of amino acids to polyols within a given dosage range yields an STI CMP polishing slurry with a removal rate selectivity of 30-80, achieving adjustable selectivity within this range. The synergistic dispersion of CeO2 in the polishing slurry by polyvinyl alcohol ensures that the polishing rate remains stable for 12 months.

[0029] The following examples and comparative examples use cerium oxide with an average particle size range of 80-100 nm and a pH of 4.0 as examples. Experiment 1: Polishing experiment with the TEOS to Si3N4 removal rate selectivity ratio controlled within the range of 30-80.

[0030] Example 1: Polishing solutions with different contents of pyridine carboxylic acid

[0031] Table 1. Composition of CeO2 polishing slurry in Example 1

[0032]

[0033] Table 2 shows a comparison of polishing solutions with only D-sorbitol or only pyridinecarboxylic acid added.

[0034] Table 2. Composition of CeO2 polishing slurry in Comparative Example 1

[0035]

[0036] The experimental results of Example 1 are shown in Tables 3 and 4.

[0037] Table 3 Experimental Results of Example 1

[0038]

[0039] Table 4 Comparative Example 1 Experimental Results

[0040]

[0041]

[0042] Comparative analysis of the experimental results of the examples and comparative examples reveals that adding only sorbitol has no effect on the removal rate of TEOS compared to using only cerium oxide abrasive, but it does inhibit the removal rate of Si3N4 to a certain extent. Adding only pyridinecarboxylic acid can simultaneously inhibit the removal rates of both TEOS and Si3N4. The experimental results of the examples and comparative examples show that the selectivity of the polishing slurry with a single additive is below 30. The polishing slurry formulation in Example 1 can achieve a TEOS to Si3N4 removal rate selectivity ratio within the range of 30-80, and the selectivity ratio can be controlled by adjusting the formulation content. The simultaneous presence of sorbitol, pyridinecarboxylic acid, and PVA10000 makes the inhibition of Si3N4 removal rate more significant, improving the selectivity ratio within the range of 30-80 while maintaining a high TEOS removal rate.

[0043] Example 2: Polishing solutions with different glutamic acid contents

[0044] Table 5. Composition of CeO2 polishing slurry in Example 2

[0045]

[0046] Table 6 shows a comparison of polishing solutions containing only glutamic acid and no polyols.

[0047] Table 6. Composition of CeO2 polishing slurry in Comparative Example 2

[0048]

[0049] The experimental results of Example 2 are shown in Tables 7 and 8.

[0050] Table 7 Experimental Results of Example 2

[0051]

[0052]

[0053] Table 8. Experimental Results of Comparative Example 2

[0054]

[0055] Comparing the experimental results of the examples and comparative examples, it can be found that the polishing solution containing only glutamic acid has a weak inhibitory effect on the removal rate of Si3N4, with a selectivity ratio below 30. The experimental results show that the polishing solution ratio in Example 2 can achieve the requirement of a TEOS to Si3N4 removal rate selectivity ratio within the range of 30-80, and the selectivity ratio can be controlled by adjusting the ratio content. Example 3: Polishing solutions with different nicotinic acid contents.

[0056] Table 9. Composition of CeO2 polishing slurry in Example 3

[0057]

[0058] The comparison of nicotinic acid alone in the polishing slurry is shown in Table 10.

[0059] Table 10 Composition of CeO2 polishing slurry in Comparative Example 3

[0060]

[0061] The experimental results of Example 3 are shown in Tables 11 and 12.

[0062] Table 11 Experimental Results of Example 3

[0063]

[0064]

[0065] Table 12 Experimental Results of Comparative Example 3

[0066]

[0067] The experimental results from the examples and comparative examples show that the polishing solution containing only nicotinic acid has a certain inhibitory effect on TEOS, but its inhibition of Si3N4 removal rate is not as strong as in Example 3, and the removal rate selectivity ratio is less than 30. The experimental results also show that the polishing solution ratio in Example 3 can achieve the requirement of a TEOS to Si3N4 removal rate selectivity ratio within the range of 30-80. Furthermore, the selectivity ratio can be controlled by adjusting the ratio of polyols and amino acids in their simultaneous presence.

[0068] Example 4: Polishing solution with modified polyol

[0069] Table 13 Composition of CeO2 polishing slurry in Example 4

[0070]

[0071] Table 14 Experimental Results of Example 4

[0072]

[0073] As can be seen from Example 4, changing the type of polyol within the range can also satisfy the 30-80 selectivity range described in this patent, implying that the polyol selected in this invention can also satisfy the adjustable removal rate selectivity within the range of 30-80.

[0074] Experiment 2: Polishing rate stability monitoring experiment based on Experiment 1

[0075] Example 5: Stability monitoring experiment of Example 1

[0076] like Figure 1 , 2 As shown, the polishing solution of Example 1 maintained a relatively stable polishing rate for TEOS and Si3N4 over a 12-month period. In Comparative Example 1, the polishing solutions of Comparative Example 1-1 and Comparative Example 1-2 maintained a relatively stable polishing rate for TEOS and Si3N4 over a 12-month period, but their selectivity was less than 30, indicating that the presence of sorbitol can improve stability, but the selectivity of a single substance is relatively low. The other comparative components only maintained the stability of the polishing rate for TEOS and Si3N4 for 2 months.

[0077] Example 6: Stability monitoring experiment of Example 2

[0078] like Figure 3 , 4 As shown, the polishing slurry of Example 2 maintained a relatively stable polishing rate for TEOS and Si3N4 over a 12-month period with minimal fluctuations, while the polishing slurry components of Comparative Example 2 maintained stable polishing rates for TEOS and Si3N4 for only 2 months.

[0079] Example 7: Stability monitoring experiment of Example 3

[0080] like Figure 5 As shown, the polishing slurry of Example 3 maintained a relatively stable polishing rate for TEOS and Si3N4 over a 12-month period. Figure 6 As shown, the polishing slurry composition of Comparative Example 3 maintained the polishing rate stability for TEOS and Si3N4 for only 3 months.

[0081] Example 8: Stability monitoring experiment of Example 4

[0082] like Figure 7 The polishing slurry of Example 4 showed that the polishing rate stability of TEOS and Si3N4 remained basically stable over a 12-month period.

[0083] Example 9: Effect of different molecular weight polyvinyl alcohols on the polishing rate stability of TEOS and Si3N4

[0084] Polishing slurry mixing ratio:

[0085] Reference proportions: CeO2 abrasive: 0.25 wt%; D-sorbitol: 0.5 wt%; pyridinecarboxylic acid: 0.25 wt%; balance: deionized water. Example 9-1: CeO2 abrasive: 0.25 wt%; D-sorbitol: 0.5 wt%; pyridinecarboxylic acid: 0.25 wt%; polyvinyl alcohol 10000: 0.02 wt%; balance: deionized water.

[0086] Example 9-2: CeO2 abrasive: 0.25wt%; D-sorbitol: 0.5wt%; pyridinecarboxylic acid: 0.25wt%; polyvinyl alcohol 20000: 0.02wt%; balance: deionized water.

[0087] Example 9-3: CeO2 abrasive: 0.25wt%; D-sorbitol: 0.5wt%; pyridinecarboxylic acid: 0.25wt%; polyvinyl alcohol 67000: 0.02wt%; balance: deionized water.

[0088] Comparative Example 9-1: CeO2 abrasive: 0.25 wt%; D-sorbitol: 0.5 wt%; pyridinecarboxylic acid: 0.25 wt%; polyvinyl alcohol 195000: 0.02 wt%; balance: deionized water.

[0089] like Figure 8 and Figure 9 As shown, the polishing slurry without polyvinyl alcohol maintained a relatively stable polishing rate for TEOS and Si3N4 within one month. The polishing slurry components shown in Examples 9-1, 9-2, and 9-3 maintained a stable polishing rate for TEOS and Si3N4 within 12 months. However, Comparative Example 9-1 could not stabilize the polishing rate of TEOS and Si3N4.

[0090] Example 10

[0091] In this embodiment, the amino acid is any two or three of glycine, alanine, aspartic acid, glutamic acid, arginine, proline, pyridinecarboxylic acid, and nicotinic acid. Other conditions are the same as in Example 1. Its stability and selectivity ratio are tested. Within the given parameter range, the formulation of this application can meet the requirement of a selectivity ratio in the range of 30-80. The polishing rate stability of TEOS and Si3N4 remains basically stable within 12 months.

[0092] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A highly stable STI CMP polishing slurry with adjustable removal rate selectivity, characterized in that: For use in STI CMP under acidic conditions of pH 2-6; The polishing slurry comprises the following components by mass percentage: CeO2 abrasive: 0.1wt%-5wt%; Amino acids: 0.1wt%-4wt%; Polyols: 0.5wt%-6wt%; Polyvinyl alcohol: 0.01wt%-1wt%; pH adjuster; balance: deionized water; The amino acid is one or more of the following: glycine, alanine, aspartic acid, glutamic acid, arginine, and proline. The polyol is one or more of the following: D-sorbitol, mannitol, lactitol, maltitol, maltotriol, xylitol, and euonymus alcohol; The synergistic effect of amino acids and polyols can achieve an adjustable TEOS / Si3N4 removal rate selectivity ratio within the range of 30-80 within a given dosage range. Combined with polyvinyl alcohol to synergistically disperse CeO2 polishing slurry, the polishing slurry can maintain a stable polishing rate within 12 months. Alternatively, the amino acid may be replaced with pyridinecarboxylic acid or nicotinic acid; The CeO2 abrasive has a particle size of 60-300 nm; the pH adjuster is an inorganic or organic acid or an inorganic or organic base; the inorganic or organic acid includes one or more of nitric acid, phosphoric acid, citric acid, oxalic acid, and acetic acid; the inorganic or organic base includes one or more of potassium hydroxide, sodium hydroxide, ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, ethanolamine, and diethanolamine. The polyvinyl alcohol is at least one of polyvinyl alcohol 10000, polyvinyl alcohol 20000, polyvinyl alcohol 27000, polyvinyl alcohol 67000, and polyvinyl alcohol 89000.

2. The high-stability STI CMP polishing slurry with adjustable removal rate selectivity according to claim 1, characterized in that: The conditions for polishing TEOS / Si3N4 using polishing slurry are: Polishing machine: Universal-150B; Polishing head / disc speed: 87 / 93 rpm; Pressure: 2.8 psi / 3 psi; Flow rate: 150 ml / min; Polishing time: 60 s; Before polishing, mix the prepared polishing solution with a high-speed mixer for 40 minutes at a speed of 3500 r / min.

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