Stabilizing concentrate and method for preparing suspensions of abrasive nanopowders based on it

Abstract

FIELD: colloidal chemistry; microelectronics.SUBSTANCE: invention can be used in the preparation of polishing suspensions for chemical-mechanical planarization (CMP) processes of semiconductor materials in the production of integrated circuits, microprocessors, memory chips and other microelectronic products. A concentrate is proposed for preparing abrasive suspensions, including a polymer additive, distilled water and a polyhydric amino alcohol selected from the group: triethanolamine, diethanolamine, monoethanolamine, 2-amino-2-methyl-1-propanol, N,N-dimethylethanolamine, in an amount of 5.0-15.0 wt.%. The polymer additive is a synthetic carboxypolymethylene selected from the group: polyacrylic acid, sodium salt of polyacrylate, cross-linked copolymers of acrylic acid with allyl esters of sugars or polyols, in an amount of 1.0-2.0 wt.%.EFFECT: increase in the aggregation and sedimentation stability of suspensions of abrasive nanopowders, adjustable viscosity and stable pH, increase in shelf life and reproducibility of properties compared to additives based on natural polysaccharides.3 cl, 15 ex

Description

[0001] The invention relates to the field of colloidal chemistry and microelectronics, in particular to the compositions of polishing suspensions used in the processes of chemical-mechanical planarization (CMP) of semiconductor materials in the production of integrated circuits, microprocessors, memory chips and other microelectronic products.

[0002] Various polymer additives are used to stabilize suspensions of abrasive nanopowders in CMP processes. There are known solutions based on natural polymers: xanthan gum (US 4161394 “Polishing slurry of xanthan gum and a dispersing agent”, IPC C09K 3 / 14, published on 17.07.1979; US 3462251 “Aqueous based lapping composition”, IPC B23F 19 / 02, C09K3 / 14, C08H 17 / 12, published on 19.08.1969), graft copolymers of polysaccharides (EP 0322721 “Fine polishing composition for wafers”, IPC C09G 1 / 02, C09K 3 / 14, H01L 21 / 304, published on 06.10.1993), carboxymethyl cellulose (EP 0377301 "Stable silica suspensions)", IPC C01B 33 / 14, C01B 33 / 141, C12H 1 / 04, B01J 13 / 00, B01J 20 / 10, published on September 22, 1999), as well as compositions of polyethylene glycol with gums (US 20060124594 "Chemical mechanical polishing (CMP) slurries and CMP methods using and making the same", IPC B24D 3 / 02, B44C 1 / 22, C09C 1 / 68, C09G 1 / 02, C09K 13 / 00, C09K 3 / 14, C23F 1 / 00, published on June 15, 2006).Their disadvantages include low reproducibility of properties, a tendency to biodegradation and a limited shelf life.

[0003] Synthetic polymers are an alternative to natural polymers. The use of non-ionic polymer additives is known, for example, copolymers of polyolefins with polyethylene glycol (CN 102648265 "Slurry composition for CMP, and polishing method)), IPC H01L21 / 304, published on 10.12.2014), as well as ionic polymers from the class of carboxylic acids - polyacrylic acid of various structures (US 8822339 "Slurry composition for CMP, and polishing method)), IPC H01L 21 / 461, published. 09 / 02 / 2014) and degree of crosslinking (US 9293344 “Cmp polishing slurry and method of polishing substrate)”), IPC B24B 1 / 00, B24B 37 / 00, C09G 1 / 02, C09K 13 / 00, C09K 3 / 14, H01L 21 / 304, H01L 21 / 3105, publ. 22.03.2016), as well as neutralized carboxypolymethylenes (US 3817727 “Abrasive polishing suspensions and method for making same”, IPC C09D 5 / 00, C09G 1 / 02, C09K 3 / 14, H01L 21 / 306, C08G 51 / 12, published 18.06.1974).The advantage of synthetic polymers is their highly reproducible properties and compositional stability compared to natural polysaccharides. Furthermore, they are resistant to biodegradation and allow for an extended shelf life of suspensions. However, they have limitations: non-ionic polymers, such as copolymers with polyethylene glycol (PEG), do not always provide a sufficient ζ-potential (electrokinetic potential), and their stabilizing effect is primarily associated with an increase in viscosity, which limits the range of working concentrations. For ionic polyacrylates, excessive cross-linking can lead to excessive viscosity growth or gelation, which reduces the processability of the suspensions.

[0004] A common drawback of existing solutions is the slow dissolution of polymer additives in the suspension medium, limited by the swelling rate of the polymer coils. Furthermore, the suspension preparation process requires adding components separately in a specific sequence, which increases labor intensity and requires qualified personnel.

[0005] The closest solution to the proposed invention is described in patent RU 2287004 ("Stabilizing additive to an abrasive suspension", IPC C09K 3 / 14, C09G 1 / 02, published on June 27, 2006). It provides for the production of a stabilizing additive based on water, glycerin, finely dispersed silicon dioxide and carboxymethyl cellulose. The advantage of this approach is the simplification of the procedure for preparing stable suspensions by combining the components in a single additive and the acceleration of polymer dissolution. However, this solution has disadvantages: the use of a biodegradable polymer matrix (carboxymethyl cellulose salt), the use of glycerin, which increases viscosity but does not affect electrokinetic stabilization, and a limited pH range (9.0-9.5). In addition, the additive is effective mainly for grinding silicon wafers and is not universal for modern CMP processes.

[0006] Thus, known solutions do not provide simultaneous achievement of high electrokinetic stability, optimal rheological properties and resistance to biodegradation.

[0007] The technical objective of the invention is to create a polymer concentrate for suspending abrasive nanopowders, ensuring aggregation and sedimentation stability of suspensions prepared from it, their adjustable viscosity and stable pH with high reproducibility of properties and resistance to biodegradation.

[0008] The technical result is achieved due to the fact that the developed concentrate for the preparation of abrasive suspensions, as well as the prototype composition, includes a polymer additive and distilled water. What is new is that the concentrate contains a polyhydric amino alcohol selected from the group: triethanolamine, diethanolamine, monoethanolamine, 2-amino-2-methyl-1-propanol, N,N-dimethylethanolamine - in an amount of 5.0-15.0 wt. %, wherein the polymer additive is a synthetic carboxypolymethylene selected from the group: polyacrylic acid, sodium salt of polyacrylate, cross-linked copolymers of acrylic acid with allyl esters of sugars or polyols - in an amount of 1.0-2.0 wt. %.

[0009] The technical result in terms of the method is achieved due to the fact that the developed method for obtaining a suspension containing abrasive particles and having a pH of 8.0-9.0, an electrokinetic potential from -20 to -40 mV and a dynamic viscosity of 150-400 mPa⋅s, includes diluting the developed concentrate in the form of a gel with water in a ratio of 1:20 with the addition of abrasive particles selected from the group: Al2O3, SiO2, CeO2, in an amount of 1-20 wt.%.

[0010] In a particular case of implementing the method for preparing a suspension that maintains sedimentation stability for at least 14 days, abrasive particles of aluminum oxide with a particle content of up to 20 wt.% are used.

[0011] This problem is solved by using a synthetic cross-linked polyacrylate (carboxypolymethylene) in combination with a polyhydric amino alcohol as a stabilizing additive. The polymer network prevents the aggregation of abrasive nanoparticles (Al2O3, CeO2, SiO2, etc.) through steric and partially electrostatic mechanisms, while the amino alcohol regulates the acid-base balance, ensuring optimal ionization of carboxyl groups and increasing the ζ-potential.

[0012] The concentrate is prepared by dispersing the polymer sample in water with vigorous stirring and adding an amino alcohol. The process is carried out at 25-30°C in a glass or polypropylene container using an overhead anchor-type stirrer (rotation speed 140-400 rpm). The finished concentrate is a transparent, homogeneous gel without foreign inclusions, odorless, with a color of 0-30 on the APHA scale. Characteristics of a 4.5% solution of the concentrate in water: density 0.995-1.000 g / cm3 , dynamic viscosity 150-400 mPa⋅s, pH 8-9.

[0013] The following polymers can be used: polyacrylic acid (PAK-37), sodium polyacrylate, MARS-06, as well as cross-linked copolymers of acrylic acid with allyl esters of sugars or polyols (e.g., Carbopol-940, Carbopol-934, Carbopol-941, Carbopol-980). The following polyhydric amino alcohols are used: triethanolamine, diethanolamine, monoethanolamine, 2-amino-2-methyl-1-propanol, N,N-dimethylethanolamine.

[0014] The implementation of the invention is illustrated by the following examples:

[0015] Example 1.

[0016] The concentrate was prepared using Carbopol-940 (1.4 wt%) and triethanolamine (8 wt%). The resulting 4.5% aqueous solution of the concentrate had a pH of 8.5 and a dynamic viscosity of 200 mPa⋅s. The electrokinetic potential of a 20% suspension of Al2O3 particles with an average size of 100 nm was -28 mV.

[0017] Example 2.

[0018] Carbopol-934 (1.5 wt%) with triethanolamine (10 wt%) was used instead of Carbopol-940. The solution had a viscosity of 380 mPa⋅s. The electrokinetic potential of a 10% suspension of Al2O3 particles with an average size of 100 nm was -30 mV.

[0019] Example 3.

[0020] The concentrate contained Carbopol-980 (1.3 wt%) and diethanolamine (6 wt%). The resulting solution had a pH of 8.3 and a viscosity of 220 mPa⋅s.

[0021] Example 4.

[0022] Carbopol-941 (1.4 wt%) was used in combination with 2-amino-2-methyl-1-propanol (AMP-95) (7 wt%). The Al2O3 suspension with an average particle size of 100 nm containing 20% ​​dispersed phase demonstrated an electrokinetic potential of -26 mV, pH 8.4, and viscosity of 180 mPa⋅s.

[0023] Example 5.

[0024] The polymer MARS-06 (1.5 wt%) and triethanolamine (12 wt%) were used. The solution demonstrated a pH of 8.8, a viscosity of 400 mPa⋅s, and the stability of the Al2O3 dispersion with an average particle size of 100 nm for at least 30 days.

[0025] Example 6.

[0026] A concentrate based on polyacrylic acid grade PAK-37 (1.4 wt.%) and N,N-dimethylethanolamine (5 wt.%). The solution had a pH of 8.2 and a viscosity of 160 mPa⋅s.

[0027] Example 7.

[0028] Sodium polyacrylate (1.3 wt%) was used in combination with triethanolamine (9 wt%). The resulting suspension, containing 20% ​​Al2O3 particles with an average size of 100 nm, had an electrokinetic potential of -25 mV and a viscosity of 190 mPa⋅s.

[0029] Example 8.

[0030] The concentrate contained Carbopol-940 (1.5 wt%) and diethanolamine (7 wt%). When diluted 1:20, an Al2O3 suspension (10 wt%, average particle size 100 nm) with a pH of 8.6 and a viscosity of 250 mPa⋅s was obtained.

[0031] Example 9.

[0032] Carbopol-980 (1.4 wt%) with triethanolamine (6 wt%) was used. The suspension containing 10% CeO2 particles with an average size of 20 nm showed an electrokinetic potential of -27 mV, a viscosity of 210 mPa⋅s, and ensured dispersion stability for 21 days.

[0033] Example 10.

[0034] The concentrate contained Carbopol-934 (1.3 wt%) and AMP-95 (10 wt%). The solution had a pH of 8.7 and a viscosity of 280 mPa⋅s. The electrokinetic potential of a 20% suspension of Al2O3 particles with an average size of 100 nm was -29 mV.

[0035] Example 11.

[0036] MARS-06 (1.4 wt%) with N,N-dimethylethanolamine (8 wt%) was used. Dilution of the concentrate yielded a SiO2 suspension (15 wt%, average particle size 120 nm) with a viscosity of 300 mPa⋅s and an electrokinetic potential of -31 mV.

[0037] Example 12.

[0038] A concentrate based on PAK-37 (1.5 wt.%) and triethanolamine (10 wt.%). The solution had a viscosity of 350 mPa⋅s and ensured the stability of an Al2O3 suspension with a particle size of 80 nm for at least 20 days.

[0039] Example 13.

[0040] Carbopol-941 (1.3 wt%) and diethanolamine (5 wt%) were used. The solution had a pH of 8.1 and a viscosity of 150 mPa. The electrokinetic potential of a 10% suspension of CeO2 particles with an average size of 20 nm was -22 mV.

[0041] Example 14.

[0042] The concentrate contained sodium polyacrylate (1.4 wt%) and triethanolamine (11 wt%). When diluted 1:20 with the addition of Al2O3 (20 wt%, average particle size 100 nm), the suspension had an electrokinetic potential of -35 mV and a viscosity of 370 mPa⋅s.

[0043] Example 15.

[0044] Carbopol-940 (1.5 wt%) with AMP-95 (9 wt%) was used. The suspension containing 20% ​​SiO2 particles with an average size of 120 nm had an electrokinetic potential of -32 mV, a pH of 8.9, a viscosity of 390 mPa⋅s, and ensured the absence of noticeable sedimentation of 90% of the SiO2 particles over 14 days.

[0045] Thus, the invention ensures the production of a gel concentrate, which, when diluted in water in a ratio of 1:20 and with the addition of aluminum oxide (or other abrasive powders), produces a suspension with increased sedimentation stability, with a stable pH value of 8-9, with a viscosity in the range of 150-400 cPa⋅s and with high ζ-potential values ​​(from -20 to -40 mV). In this case, to obtain the concentrate, a polyhydric amino alcohol in an amount of 5.0-15.0 wt. % and synthetic carboxypolymethylene in an amount of 1.0-2.0 wt. % are mixed, and to obtain the suspension, abrasive particles are added in an amount of 1-20 wt. %.

Claims

1. A concentrate for preparing abrasive suspensions, including a polymer additive and distilled water, characterized in that it contains a polyhydric amino alcohol selected from the group: triethanolamine, diethanolamine, monoethanolamine, 2-amino-2-methyl-1-propanol, N,N-dimethylethanolamine, in an amount of 5.0-15.0 wt.%, wherein the polymer additive is a synthetic carboxypolymethylene selected from the group: polyacrylic acid, sodium salt of polyacrylate, cross-linked copolymers of acrylic acid with allyl esters of sugars or polyols, in an amount of 1.0-2.0 wt.%.

2. A method for producing a suspension containing abrasive particles and having a pH of 8.0-9.0, an electrokinetic potential of -20 to -40 mV and a dynamic viscosity of 150-400 mPa⋅s, comprising diluting the concentrate according to item 1 in the form of a gel with water in a ratio of 1:20 with the addition of abrasive particles selected from the group: Al2O3, SiO2, CeO2, in an amount of 1-20 wt.%.

3. A method for producing a suspension according to paragraph 2, characterized in that abrasive particles of aluminum oxide with a particle content of up to 20% by weight are used to prepare a suspension that maintains sedimentation stability for at least 14 days.