Tungsten chemical mechanical polishing composition and application thereof

Abstract

The invention discloses a tungsten chemical mechanical polishing composition and application thereof. The tungsten chemical mechanical polishing composition comprises an abrasive, a catalyst, an oxidizing agent, a stabilizing agent, a corrosion inhibitor and water. Wherein the surface of the abrasive material is treated by a hydrophilic high-molecular polymer, and the abrasive material has a Zeta potential of which the absolute value is less than 3mV. When the tungsten chemical-mechanical polishing composition is used for tungsten chemical-mechanical polishing, strong electrostatic adsorption between the composition and the surface of a polished tungsten wafer is avoided, and the problem of particle residue after polishing can be effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical mechanical polishing, and in particular relates to a chemical mechanical polishing composition and application thereof in chemical mechanical polishing of tungsten. Background Art

[0002] As the size of semiconductor devices gradually decreases and the number of metal layers continues to increase, the chemical mechanical polishing technology of metal layers and insulating dielectric layers becomes particularly critical.

[0003] During the chemical mechanical polishing (CMP) process, the upper surface of the substrate is in direct contact with the polishing pad and rotates relative to the polishing pad under a certain pressure. At the same time, a mixture containing abrasives (commonly called polishing liquid) is applied to the surface of the polishing pad to achieve flattening of the substrate surface with the help of the chemical corrosion effect of the polishing liquid and the mechanical action of the abrasive.

[0004] As one of the objects of chemical mechanical polishing (CMP), metal tungsten has strong resistance to electron migration under high current density, excellent hole filling ability, and can form a good ohmic contact with silicon. Therefore, it can be used as a filling metal and diffusion barrier layer for contact windows and vias.

[0005] As the feature size of semiconductor devices continues to shrink, it becomes more difficult to meet device requirements (including flattening and defects) in tungsten CMP. For example, scratches caused by agglomeration of polishing liquid abrasives and residual particles caused by adsorption of abrasive particles on the wafer surface. U.S. Patent No. 62823258 uses small molecule diols as dispersants to improve the stability of the polishing liquid, and there is no restriction on the Zeta potential of the abrasive. The abrasive in U.S. Patent No. 10676647 has a Zeta potential of 10-40mV, which is stable under acidic conditions, but the residual particle phenomenon after polishing is still serious.

[0006] Therefore, there is a need to continuously develop new chemical mechanical polishing compositions that enhance the dimensional stability of abrasives while reducing particle residue after polishing. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a new tungsten chemical mechanical polishing composition to improve the agglomeration of abrasives under acidic conditions and adsorption after polishing, thereby improving the surface quality of polished wafers.

[0008] Another object of the present invention is to provide application of the chemical mechanical polishing composition in chemical mechanical polishing of tungsten.

[0009] In order to achieve the above invention object, the present invention adopts the following technical scheme:

[0010] A tungsten chemical mechanical polishing composition comprises an abrasive, a catalyst, an oxidant, a stabilizer, a corrosion inhibitor and water; wherein the surface of the abrasive is treated with a hydrophilic high molecular polymer and has a Zeta potential with an absolute value of less than 3mV.

[0011] In a specific embodiment, the tungsten chemical mechanical polishing composition includes, by mass percentage, 1-10% abrasive, 0.001-0.1% catalyst, 1.5-2.5% oxidant, 0.01-0.2% stabilizer, 0.01-0.2% corrosion inhibitor, and water;

[0012] In a preferred embodiment, the composition comprises 1-5% of abrasive, 0.01-0.1% of catalyst, 2.0% of oxidant, 0.05-0.2% of stabilizer, 0.01-0.1% of corrosion inhibitor, and the balance is water.

[0013] In a specific embodiment, the hydrophilic high molecular polymer is a polyether, preferably, the polyether is a modified polyether, more preferably, the modified group of the modified polyether is siloxane, and the content of the hydrophilic high molecular polymer relative to the mass of the abrasive is 1-10%.

[0014] In a specific embodiment, the abrasive is silica sol or fumed silica; preferably, the silica abrasive is silica sol, and preferably the particle size of the abrasive is 40-200 nm.

[0015] In a specific embodiment, the catalyst is an iron salt that can ionize iron ions in aqueous solution; preferably iron nitrate.

[0016] In a specific embodiment, the stabilizer is an organic acid; preferably one or more selected from acetic acid, citric acid, tartaric acid, oxalic acid, lactic acid, malic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, maleic acid, glycolic acid, diglycolic acid, glyceric acid, and succinic acid; more preferably malonic acid.

[0017] In a specific embodiment, the corrosion inhibitor is one or more of α-amino acids or nitrogen-containing heterocycles. More specifically, the α-amino acids are selected from one or more of glycine, alanine, glutamic acid, leucine, tyrosine, serine, histidine, valine, lysine or arginine; preferably selected from one or both of glycine or lysine. The nitrogen-containing heterocycle is selected from one or more of 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, 5-amino-1H-tetrazolyl, 2-aminomethylpyridine, 4-aminopyridine, 2-aminopyrimidine, adenine or N-aminoethylpiperazine.

[0018] In a specific embodiment, the oxidizing agent is hydrogen peroxide.

[0019] In a specific embodiment, the pH of the chemical mechanical polishing composition is 2.0-2.5.

[0020] Another aspect of the present invention is the use of the aforementioned tungsten chemical mechanical polishing composition in tungsten chemical mechanical polishing.

[0021] By adopting the above technical solution, the present invention can achieve the following beneficial effects:

[0022] In the tungsten chemical mechanical polishing composition of the present invention, the abrasive surface is treated with a hydrophilic polymer and has a Zeta potential with an absolute value of less than 3mV. The hydrophilic polymer forms a hydration layer on the abrasive surface, providing sufficient steric hindrance, so that the abrasive can have excellent stability even under acidic conditions and reduce abrasive agglomeration; at the same time, the absolute value of the Zeta potential is within 3mV, and there will be no strong electrostatic adsorption with the surface of the polished tungsten wafer, which can effectively reduce the problem of residual particles after polishing. DETAILED DESCRIPTION

[0023] In order to better understand the technical solution of the present invention, the following examples will further illustrate the method provided by the present invention, but the present invention is not limited to the listed examples, and should also include any other known changes within the scope of the claims of the present invention.

[0024] A tungsten chemical mechanical polishing composition comprises 1-10% by mass of silica abrasive, 0.001-0.1% of iron salt catalyst, 1.5-2.5% of oxidant, 0.01-0.2% of stabilizer, 0.01-0.2% of corrosion inhibitor, and the balance is water; wherein the surface of the abrasive is treated with a hydrophilic polymer and has a Zeta potential with an absolute value of less than 3mV. Preferably, the chemical mechanical polishing composition comprises 1-5% of silica abrasive, 0.01-0.1% of iron salt catalyst, 2.0% of oxidant, 0.05-0.2% of stabilizer, 0.01-0.1% of corrosion inhibitor, and the balance is water.

[0025] Specifically, the hydrophilic high molecular polymer is a polyether, preferably, the polyether is a modified polyether, and more preferably, the modified group of the modified polyether is siloxane.

[0026] The amount of the hydrophilic high molecular polymer added is 1-10% of the mass of the abrasive, for example including but not limited to 1%, 3%, 5%, 7%, 9%, 10%.

[0027] Specifically, the hydrophilic polymer may be selected from the commercially available SilwetTM A surfactant of the family, for example, may be selected from Silwet TM L-7210、Silwet TM L-7220、Silwet TM L-7230、Silwet TM L-8610、Silwet TM L-7608、Silwet TM L-7280.

[0028] The hydrophilic polymer may be selected from XIAMETER TM Series products, such as those available from XIAMETER TM OFX-3667, XIAMETER TM OFX-0190, XIAMETER TM OFX-5098, XIAMETER TM OFX-5220, XIAMETER TM OFX-5329, XIAMETER TM OFX-5330, XIAMETER TM OFX-5211.

[0029] The hydrophilic polymer may be selected from Dow Chemical's commercialized DOWSIL TM Series products, such as those available from DOWSIL TM Q4-3669、DOWSIL TM 5562、DOWSIL TM OFX-0400、DOWSIL TM 1248、DOWSIL TM OFX-5247、DOWSIL TM 5604、DOWSIL TM Q2-5212.

[0030] The hydrophilic polymer may be selected from VORASURF commercialized by Dow Chemical (Dow) TM Series and SYLGARD TM Series products, such as those available from VORASURF TM DC 5103, VORASURF TM TF 5067、SYLGARD TM OFX-0309.

[0031] Preferably, the HLB value of the hydrophilic polymer is greater than 9, and more preferably, the HLB value of the hydrophilic polymer is greater than 10.

[0032] The hydrophilic polymer siloxane end is covalently bonded to the surface of the silica abrasive through a Si-O-Si bond, and the polyether end extends outside the abrasive to form a hydration layer, which brings about a steric hindrance sufficient to stabilize the abrasive under acidic conditions.

[0033] In the present invention, there is no particular limitation on the treatment method of the abrasive surface treated with a hydrophilic polymer. For example, the hydrophilic polymer is dissolved in water to form a 1% aqueous solution, and the pH is adjusted to 2-3 with nitric acid; then the acidic aqueous solution of the hydrophilic polymer is further diluted according to the required concentration, and the pH of the dilution is adjusted to 9-10 with KOH, then the abrasive is added, and the stirring is continued for 30 minutes; the abrasive treated as above is mixed with an auxiliary agent system to obtain the polishing liquid of the present invention. It can be understood by those skilled in the art that the abrasive surface is not treated with a hydrophilic polymer. In fact, the key lies in the selection of the hydrophilic polymer. The treatment process only requires the hydrophilic polymer and the abrasive to be fully stirred and mixed. For example, the polymer is mixed with other auxiliary agents, then the abrasive is added and stirred for 30 minutes, and then it is used after standing for 7 days.

[0034] The abrasive is silica sol or fumed silica, preferably silica sol. The amount of the abrasive added is generally 1-10% of the total mass of the polishing liquid, for example including but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%. Preferably, the amount of the abrasive added is 1-5% of the total mass of the polishing liquid.

[0035] The silica sol has a particle size of 40-200 nm. Preferably, the silica sol has a particle size of 60-120 nm. The silica sol may be any silica sol that meets the requirements, for example, it may be purchased from Nissan Chemical, Fuso, Dupont and Bayer, etc. Preferably, the silica sol is selected from Fuso's PL-3, PL-5 or PL-7 (secondary particle sizes are 70, 100 and 120 nm, respectively).

[0036] The amount of the iron salt catalyst added is generally 0.001%-0.1% of the total mass of the polishing liquid, for example including but not limited to 0.001%, 0.005%, 0.01%, 0.05%, 0.07%, 0.1%. Preferably, the amount of the iron salt catalyst added is 0.01%-0.1% of the total mass of the polishing liquid.

[0037] The stabilizer is an organic acid selected from one or more of acetic acid, citric acid, tartaric acid, oxalic acid, lactic acid, malic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, maleic acid, glycolic acid, diglycolic acid, glyceric acid, and succinic acid; preferably malonic acid. The amount of the stabilizer added is generally 0.01-0.2% of the total mass of the polishing liquid, for example, including but not limited to 0.01%, 0.015%, 0.05%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, preferably, the amount of the stabilizer added is 0.05-0.2% of the total mass of the polishing liquid.

[0038] The corrosion inhibitor is one or more of α-amino acids or nitrogen-containing heterocycles; wherein the α-amino acids are selected from one or more of glycine, alanine, glutamic acid, leucine, tyrosine, serine, histidine, valine, lysine or arginine; preferably selected from one or two of glycine or lysine. The nitrogen-containing heterocycle is selected from one or more of 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, 5-amino-1H-tetrazole, 2-aminomethylpyridine, 4-aminopyridine, 2-aminopyrimidine, adenine or N-aminoethylpiperazine. The amount of the corrosion inhibitor added is generally 0.01-0.2% of the total mass of the polishing liquid, for example, including but not limited to 0.01%, 0.015%, 0.05%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, preferably, the amount of the corrosion inhibitor added is 0.01-0.1% of the total mass of the polishing liquid.

[0039] The oxidant is usually hydrogen peroxide, and the amount of the oxidant added is generally 2.0%, which is usually added separately before use to avoid premature decomposition. The pH of the chemical mechanical polishing composition is adjusted to 2.0-2.5 by nitric acid or potassium hydroxide.

[0040] The present invention is further explained below by more specific examples, but does not constitute any limitation.

[0041] Unless otherwise specified, the main raw materials used in the following examples are common commercial products.

[0042] Table 1 shows the composition and content of the tungsten polishing liquid in comparative examples 1 to 5 and embodiments 1 to 12 of the present invention. According to Table 1, the chemical mechanical polishing liquid is prepared by simple stirring and mixing. After mixing evenly, the pH value is adjusted to 2.5 with nitric acid or KOH. Before use, hydrogen peroxide is added and mixed evenly, and the balance is supplemented with water to 100%, thereby obtaining various embodiments and comparative examples of the present invention.

[0043] Among them, the content of the high molecular polymer is measured by mass relative to the abrasive. In comparative example 1, PL-7 is treated with an aminosilane compound to have a permanent positive charge of 9 mV, in comparative example 2, PL-5 is treated with mercaptosilane to have a permanent negative charge of -15 mV, and in comparative example 4, PL-3 is treated with an aminosilane compound to have a permanent positive charge of 25 mV.

[0044] Preparation Example

[0045] A hydrophilic polymer is dissolved in water to form a 1% aqueous solution, and the pH is adjusted to 2-3 with nitric acid; the acidic aqueous solution of the hydrophilic polymer is then further diluted according to the required concentration, and the pH of the dilution is adjusted to 9-10 with KOH, and then an abrasive is added and stirred for 30 minutes; the abrasive treated as above is mixed with the auxiliary agent system to obtain the polishing liquid of the embodiment of the present invention.

[0046] Table 1 Polishing liquid composition table of comparative examples 1 to 5 and embodiments 1 to 12

[0047]

[0048]

[0049]

[0050] In order to verify the stability of the polishing liquid of the present invention, after the polishing liquid was prepared according to Table 1, the initial particle size and large particle value were tested using a Malvern Panalytical (Malvern) particle size analyzer and an AccuSizer A9000 FXNANO (PSS) large particle counter, respectively, and then tested again after standing and aging at 40°C for 1 week. The results are shown in Table 2. Among them, the large particle data is the total number of particles with a particle size greater than 0.56 μm.

[0051] Table 2 Particle size and large particle changes of comparative examples and examples

[0052]

[0053] The results in Table 2 show that after the polishing liquids of Examples 1 to 12 of the present invention were aged at 40°C for one week, the average particle size of the abrasive particles changed within 2 nm (due to the existence of measurement errors, it can be considered that there is basically no change). No hydrophilic polymer or dispersant was added to Comparative Examples 1 to 3, and the abrasives did not have permanent positive charges under acidic conditions. The particle size had increased to a certain extent at the beginning of the preparation of the polishing liquid, and the particle size increased rapidly after aging. Comparative Examples 4 and Comparative Examples 5 had relatively good stability due to electrostatic repulsion and steric hindrance, respectively, and the particle size did not change significantly. It can be seen from the particle size that Comparative Examples 1 to 3 agglomerated severely after aging, and to avoid contaminating the instrument, no large particle test was performed. After one week of high temperature aging, the number of large particles above 0.56 μm in Comparative Examples 4 and Examples 1 to 12 was within 10% of the initial state, indicating that the particles were in a stable state and not easy to agglomerate. Although the particle size of Comparative Example 5 is the same as that of the initial state, the large particles increase to more than 300% of the original, which indicates that the particles have been agglomerated at the microscopic level, and the particle size will inevitably increase with the extension of time.

[0054] In order to verify the polishing effect of the polishing solution of the present invention, polishing was performed using the polishing solutions of Comparative Examples 1 to 5 and Examples 1 to 12.

[0055] The wafers used for polishing include 300mm W and TEOS blank coated wafers, both of which are purchased from Ramco, an American company, which is an authoritative test wafer supplier worldwide.

[0056] The polishing conditions are as follows: the polishing machine is 12" Reflexion LK, the polishing pad is IC1010, the polishing pressure is 3.0 psi, the polishing head and polishing disc rotation speed is 93 / 87 rpm, the polishing liquid flow rate is 250 mL / min, and the polishing steps are firstly to use the polishing composition of the present invention to polish the W sheet for 60 s, and then to use the commercial Wbuff polishing liquid W7300 to polish the TEOS sheet for 40 s, and 1% ammonia solution is used as the cleaning liquid.

[0057] The defects of TEOS wafers with a size of more than 120 nm after polishing were detected using the KLA SP2 machine, and the scratches and residuals were automatically identified using the KLASEM machine. The statistical test results are shown in Table 3.

[0058] Table 3 Defect statistics of comparative examples 1 to 5 and embodiments 1 to 12

[0059]

[0060]

[0061] As shown in Table 3, the total number of defects, scratches and residues of Examples 1 to 12 are all maintained at a low level. Comparative Example 3 does not stabilize the abrasive by electrostatic repulsion or steric hindrance. As shown in Table 2, the particle size of the polishing composition changes at the beginning of its preparation, indicating that the abrasive has been agglomerated to a certain extent. Therefore, even if polishing is performed immediately after preparation, the defects of the polished wafer are still at a high level, 2 to 3 times that of the embodiment. The total number of defects of Comparative Examples 1 and Comparative Examples 4 is about 50% higher than that of Examples 1 to 12, indicating that the surface effect after polishing is better, and the scratch performance is almost the same as that of the embodiment. However, since the abrasive surface is positively charged, it has strong electrostatic adsorption with the TEOS surface and is difficult to be removed during cleaning, so the residual after polishing is significantly higher than that of the embodiment. The number of scratches in Comparative Example 2 is significantly higher than that of the embodiment, because its surface is negatively charged, and it has strong electrostatic repulsion with the wafer surface during polishing. The material is mainly removed by mechanical action, resulting in more mechanical scratches. The total number of defects in Comparative Example 5 is only about half of that in Comparative Examples 1 to 3, indicating that after the addition of conventional nonionic surfactants, the steric hindrance introduced by the combination with the abrasive has a certain effect on maintaining the stability of the abrasive, but the surface properties in all aspects are still significantly worse than those in Examples 1 to 12.

[0062] In summary, when the chemical mechanical polishing composition of the present invention is used for chemical mechanical polishing of tungsten, it can enhance the stability of the abrasive, significantly reduce the number of defects, especially reduce scratches and residues, and improve the surface quality of the polished wafer.

[0063] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. Those skilled in the art will appreciate that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A tungsten chemical mechanical polishing composition, characterized in that: The invention comprises an abrasive, a catalyst, an oxidant, a stabilizer, a corrosion inhibitor and water; wherein the surface of the abrasive is treated with a hydrophilic high molecular polymer and has a Zeta potential with an absolute value of less than 3mV.

2. The tungsten chemical mechanical polishing composition according to claim 1, characterized in that: The tungsten chemical mechanical polishing composition comprises, by mass percentage, 1-10% of abrasive, 0.001-0.1% of catalyst, 1.5-2.5% of oxidant, 0.01-0.2% of stabilizer, 0.01-0.2% of corrosion inhibitor, and water; Preferably, it comprises 1-5% of abrasive, 0.01-0.1% of catalyst, 2.0% of oxidant, 0.05-0.2% of stabilizer, 0.01-0.1% of corrosion inhibitor, and the balance is water.

3. The tungsten chemical mechanical polishing composition according to claim 1 or 2, characterized in that: The hydrophilic high molecular polymer is a polyether, preferably a modified polyether, and more preferably a siloxane-modified polyether.

4. The tungsten chemical mechanical polishing composition according to any one of claims 1 to 3, characterized in that: The hydrophilic high molecular polymer has a content of 1-10% relative to the mass of the abrasive.

5. The tungsten chemical mechanical polishing composition according to any one of claims 1 to 4, characterized in that: The abrasive is silica sol or fumed silica, and preferably the particle size of the abrasive is 40-200 nm.

6. The tungsten chemical mechanical polishing composition according to any one of claims 1 to 5, characterized in that: The catalyst is an iron salt that can ionize iron ions in an aqueous solution, preferably iron nitrate.

7. The tungsten chemical mechanical polishing composition according to any one of claims 1 to 6, characterized in that: The stabilizer is an organic acid; preferably one or more selected from acetic acid, citric acid, tartaric acid, oxalic acid, lactic acid, malic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, maleic acid, glycolic acid, diglycolic acid, glyceric acid, and succinic acid, more preferably malonic acid.

8. The tungsten chemical mechanical polishing composition according to any one of claims 1 to 7, characterized in that: The corrosion inhibitor is one or more of α-amino acids or nitrogen-containing heterocycles; Preferably, the α-amino acid is selected from one or more of glycine, alanine, valine, leucine, methyltyrosine, isoleucine, methionine, proline, tryptophan, serine, tyrosine, cysteine, phenylalanine, asparagine, glutamine, threonine, aspartic acid, glutamic acid, N-methylglycine, lysine, arginine, and histidine; preferably selected from one or both of glycine and arginine; and / or The nitrogen-containing heterocycle is selected from one or more of 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, 5-amino-1H-tetrazolyl, 2-aminomethylpyridine, 4-aminopyridine, 2-aminopyrimidine, adenine, and N-aminoethylpiperazine.

9. The tungsten chemical mechanical polishing composition according to any one of claims 1 to 8, characterized in that: The oxidant is hydrogen peroxide; Preferably, the pH of the tungsten chemical mechanical polishing composition is 2.0-2.

5.

10. Use of the tungsten chemical mechanical polishing composition according to any one of claims 1 to 9 in tungsten chemical mechanical polishing.

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