Copper chemical mechanical polishing solution and application thereof

Abstract

The invention provides a chemical mechanical polishing solution for copper and application thereof. According to the copper chemical mechanical polishing solution, the specific corrosion inhibitor is adopted, the flexible alkyl chain is connected with the two benzotriazole groups, and not all the benzotriazole groups are adsorbed on the surface of copper when the copper chemical mechanical polishing solution is polished under high pressure, so that a relatively high polishing rate is obtained, and the copper chemical mechanical polishing solution is relatively high in corrosion resistance when the copper chemical mechanical polishing solution is polished under low pressure. More benzotriazole groups are adsorbed on the surface of copper, so that the polishing rate is reduced, and the chemical mechanical polishing solution for copper can meet the use requirement that the previous two steps of polishing are combined into one step of polishing of copper metal. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the field of chemical engineering, and relates to a chemical mechanical polishing (CMP) liquid, in particular to a chemical mechanical polishing liquid for copper interconnect wiring in semiconductor manufacturing processes and its applications. Background Art

[0002] With the rapid development of the integrated circuit industry, large-scale integrated circuits (GLSIs) have been mass-produced internationally. The wafer diameter is 450 mm, and the number of metal interconnect layers is up to 10 or more. To ensure that various parameters of the wafer and even the device performance meet the fundamental requirements, a high wafer surface flatness needs to be achieved after each layer of wiring. Chemical mechanical polishing (CMP) is currently considered the best method to achieve local and global planarization of the wafer surface. In principle, CMP is a polishing technology that utilizes the synergistic effect of chemical reactions and mechanical forces to achieve the best polishing effect. During the CMP process of copper wiring, the composition and properties of the polishing liquid are the decisive factors for obtaining a high-quality polished surface.

[0003] The components in the copper polishing liquid generally include abrasive particles, corrosion inhibitors, complexing agents, wetting agents, pH regulators, oxidants, etc. During the CMP process, the corrosion inhibitor mainly forms a dense protective film on the metal surface through physical adsorption or chemical adsorption. Van der Waals forces play a major role in physical adsorption, and chemical bonds play a major role in chemical adsorption. The latter is mainly due to the breaking of chemical bonds on the wafer surface during the polishing process, with high energy, and urgently needs to adsorb a layer of substances to form new bonds to promote the surface to reach a stable state. To achieve a high removal rate, a weak corrosion inhibitor is usually selected, and the polishing rate is controlled by changing the polishing pressure.

[0004] The chemical mechanical polishing process of copper is divided into three steps, which are carried out on three polishing pads respectively: in the first step, a relatively high downward pressure is used to quickly and efficiently remove a large amount of copper on the substrate surface and leave a certain thickness of copper; in the second step, a relatively low downward pressure is used to remove a small amount of remaining metallic copper at a lower removal rate and stop at the barrier layer; in the third step, the barrier layer polishing liquid is used to remove the barrier layer, part of the dielectric layer, and a small amount of metallic copper, thereby achieving planarization. Currently, to effectively remove metallic copper, sufficient polishing time must be ensured in the first and second polishing steps; at the same time, to correct the dish-shaped depression caused by copper polishing, sufficient time is also required for the third-step barrier layer polishing, which makes the copper polishing process a bottleneck in production capacity.

[0005] In order to improve the polishing rate, attempts are being made to combine the first two polishing steps of copper into one step. However, the polishing pressure in the first step is relatively high (1.5 - 2.0 psi), while the polishing pressure in the second step is relatively low (0.5 - 1.0 psi). Generally, two different components of copper polishing solutions are required to cooperate with different polishing pressures for two-step polishing. However, when these two steps are combined into one step (high pressure first and then low pressure) for polishing, the existing polishing solutions cannot meet the polishing requirements. The reason is as follows: When the first two polishing steps are carried out separately, under high polishing pressure, the role of the corrosion inhibitor is weak and the polishing rate is very fast; under low polishing pressure, the corrosion inhibitor can be fully adsorbed on the copper surface, which can play a certain role in reducing the polishing rate and the polishing rate is relatively slow. When these two steps are combined into one step (high pressure first and then low pressure) for polishing, after the high pressure is converted to low pressure, the corrosion inhibitor cannot be fully adsorbed on the copper surface, and after polishing at high pressure for a certain period of time, the temperature of the polishing pad is relatively high, which accelerates the corrosion rate of the copper surface, resulting in a relatively high polishing rate under low pressure and affecting the planarization effect.

[0006] Therefore, the development of chemical mechanical polishing solutions that can adapt to the new CMP method is a current research hotspot. Summary of the Invention

[0007] Aiming at the problems existing in the prior art, the present invention provides a new copper chemical mechanical polishing solution. By optimizing the corrosion inhibitor, it has a relatively fast polishing rate when polishing under high pressure, and can reduce the polishing rate when polishing under low pressure, which can meet the use requirements of combining two steps into one step for polishing, and has the effects of simplifying the polishing process flow and improving production capacity.

[0008] In a first aspect, the present invention provides a chemical mechanical polishing solution, comprising 0.5% - 3% by mass of abrasive particles, 0.01% - 3% of corrosion inhibitor, 1% - 20% of complexing agent, 0.005% - 3% of surfactant, pH regulator and 0.1% - 1% of oxidant, with the balance being solvent; The corrosion inhibitor is selected from one compound or a mixture of multiple compounds of the compound of formula (I);

[0009] In formula (I), R1 - R4 are independently selected from hydrogen, C1 - C12 alkyl, C6 - C20 aryl; L is selected from C1 - C6 alkylene.

[0010] In one embodiment, the chemical mechanical polishing solution is a copper chemical mechanical polishing solution.

[0011] In one embodiment, R1-R4 are independently selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, phenyl, naphthyl, biphenyl.

[0012] In one embodiment, L is selected from -(CH2) n -, and n is 1, 2, 3, 4, 5 or 6.

[0013] In one embodiment, the compounds of formula (I) are selected from: , , , , .

[0014] In one embodiment, the mass fraction of the corrosion inhibitor is 0.1% - 2%, preferably 0.5% - 1.5%.

[0015] In one embodiment, the solvent includes water, or a mixture of water and an organic solvent.

[0016] Preferably, the organic solvent is selected from aliphatic alcohols; more preferably, the organic solvent is selected from methanol, ethanol, propanol, butanol, pentanol, hexanol, ethylene glycol, glycerol; most preferably, the organic solvent is selected from n-butanol.

[0017] Preferably, in the mixture of water and an organic solvent, the mass ratio of water to the organic solvent is 1 - 5:1, preferably 1.2 - 4:1, more preferably 1.7 - 2.2:1.

[0018] In one embodiment, the abrasive particles are silica nanoparticles or alumina nanoparticles.

[0019] Preferably, the particle size of the abrasive particles is 30 - 250 nm, preferably 150 - 200 nm.

[0020] Preferably, in the chemical mechanical polishing liquid, the mass fraction of the abrasive particles is 0.5% - 2%, more preferably 1% - 2%.

[0021] In one embodiment, the complexing agent is selected from one or more of arginine, lysine, glycine, citric acid, phosphoric acid, aminotrimethylenephosphonic acid, hydroxyethanediphosphonic acid, ethylenediaminetetramethylenephosphonic acid, hydroxyethanediphosphonic acid, preferably glycine.

[0022] Preferably, in the chemical mechanical polishing liquid, the mass fraction of the complexing agent is 3% - 10%, more preferably 5% - 8%.

[0023] In one embodiment, the surfactant is a polymeric anionic surfactant. Preferably, the surfactant is selected from one or more of carboxylate-sulfonate copolymers, carboxylate-sulfonate-nonionic copolymers, and carboxylate-sulfonate-acrylate copolymers having a hydrophilic-lipophilic balance value (HLB value) of 15 to 30. More preferably, the salt is potassium salt and / or sodium salt. Most preferably, the surfactant is a carboxylic acid-sulfonate copolymer kr-5000.

[0024] Preferably, in the chemical mechanical polishing liquid, the mass fraction of the surfactant is 0.1% to 2%, more preferably 0.5% to 1.5%.

[0025] In one embodiment, the pH regulator is selected from one or more of H3PO4, HNO3, potassium hydroxide, and ammonium hydroxide. Preferably, the pH range of the chemical mechanical polishing liquid after adjustment is 5 to 8, and preferably, the pH range is 6 to 7.

[0026] In one embodiment, the oxidizing agent is hydrogen peroxide.

[0027] Preferably, in the chemical mechanical polishing liquid, the mass fraction of the oxidizing agent is 0.2% to 0.8%, more preferably 0.3% to 0.5%.

[0028] The present invention also provides a preparation method of a chemical mechanical polishing liquid, and the method includes: (1) uniformly mixing a solvent, abrasive particles, a corrosion inhibitor, a complexing agent, and a surfactant; (2) adjusting the pH value to 5 to 8 with a pH regulator; (3) adding an oxidizing agent to obtain the chemical mechanical polishing liquid.

[0029] The present invention also provides a compound of formula (I):

[0030] In formula (I), R1-R4 independently selected from hydrogen, C1-C12 alkyl, C6-C20 aryl; L is selected from C1-C6 alkylene; provided that the compound is not .

[0031] In one embodiment, R1-R4 independently selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, phenyl, naphthyl, biphenyl.

[0032] In one embodiment, L is selected from -(CH2) n -, and n is 1, 2, 3, 4, 5 or 6.

[0033] In one embodiment, the compounds of formula (I) are selected from: , , , .

[0034] The present invention also provides a method for synthesizing the compounds of formula (I), comprising the following steps:

[0035] Reacting a compound of formula (II) with a compound of formula (III) to obtain a compound of formula (I); wherein, L1 and L2 are independently selected from a single bond and C1-C6 alkylene, and L1 and L2 are not both single bonds; X1 and X2 are independently selected from chlorine and bromine; R1-R4 are independently selected from hydrogen, C1-C12 alkyl, and C6-C20 aryl; L is selected from C1-C6 alkylene.

[0036] The present invention also provides the use of the compounds of formula (I) in the field of chemical mechanical polishing, especially in the field of chemical mechanical polishing of copper.

[0037] The present invention also provides the use of the chemical mechanical polishing liquid in the field of chemical mechanical polishing, especially in the field of chemical mechanical polishing of copper.

[0038] The present invention also provides a method for polishing copper, comprising the following steps: (1) Using the chemical mechanical polishing liquid of the present invention, removing copper on the surface of the substrate under high pressure and low pressure conditions in sequence and stopping at the barrier layer; (2) Removing the barrier layer, a part of the dielectric layer and a small amount of metallic copper with a barrier layer polishing liquid.

[0039] In one embodiment, the high pressure condition is 1.5-2.0 psi, and the low pressure condition is 0.5-1.0 psi.

[0040] In one embodiment, polishing is carried out for 1-3 min under high pressure conditions, preferably 0.5-1.5 min; then polishing is carried out for 1-3 min under low pressure conditions, preferably 0.5-1.5 min. Beneficial effects

[0041] The copper chemical mechanical polishing solution of the present invention uses a specific corrosion inhibitor. This corrosion inhibitor contains two benzotriazole groups, and the two benzotriazole groups are connected by a flexible alkyl chain. When polishing under high pressure, not all benzotriazole groups are adsorbed on the surface of copper, thus obtaining a relatively fast polishing rate. When polishing under low pressure, more benzotriazole groups are adsorbed on the surface of copper, thereby reducing the polishing rate. This enables the copper chemical mechanical polishing solution of the present invention to meet the usage requirements of combining the first two steps of copper metal polishing into one step (high pressure first and then low pressure). In addition, the addition of fatty alcohol solvent is beneficial to further improving the high-pressure polishing rate. For the corrosion inhibitor with benzotriazole groups connected by flexible bonds of different chain lengths, the extended flexible chain can further improve the polishing rate under high pressure, thereby improving the polishing efficiency, and can also greatly improve the long-term stability of the polishing solution, having higher application value. Detailed implementation mode

[0042] The present invention is described in more detail below to facilitate the understanding of the present invention.

[0043] The experimental methods in the following examples are all conventional methods unless otherwise specified. For those not indicating specific techniques or conditions in the examples, they are carried out according to the techniques or conditions described in the literature in this field or according to the product specifications.

[0044] Synthesis example:

[0045] Under nitrogen protection, 9 grams of 5-(bromomethyl)-1H-benzo[d][1,2,3]triazole, 1.5 grams of zinc powder, and 100 milliliters of tetrahydrofuran were added to a three-necked flask, stirred at 50 °C for 4 hours, then 0.5 grams of nickel chloride was added, stirred at 50 °C for 24 hours, cooled, ethyl acetate and water were added, filtered, the mother liquor was separated, and the organic layer was concentrated and then crystallized with ethanol to obtain 1.7 grams of compound 1,2-bis(1H-benzo[d][1,2,3]triazol-5-yl)ethane. Mass spectrometry MS-ESI: 265.11 [M+H] + 。

[0046] Elemental analysis values: C, 63.57%, H, 4.56%, N, 31.80% (theoretical values C, 63.62%; H, 4.58%; N, 31.80%).

[0047] Example: The composition of the copper chemical mechanical polishing solution is shown in Table 1 below. Each part is in mass parts. Stir and mix all components evenly, and adjust the pH value to 6 with 10% potassium hydroxide aqueous solution. Add the oxidant before use and mix evenly. The oxidant used is hydrogen peroxide, and the hydrogen peroxide (the amount of pure hydrogen peroxide) accounts for 0.4% of the total weight of the copper chemical mechanical polishing solution. Among them, the surfactant kr-5000 is purchased from Shandong Kerry Chemical Co., Ltd.

[0048] Table 1: Composition of Copper Chemical Mechanical Polishing Solutions for Comparative Examples and Examples

[0049] The specific polishing conditions are as follows: The polishing machine is a 12” Reflexion LK, and the polishing pad is IC1010; the high polishing pressure is 2.0 psi, and the low polishing pressure is 1.0 psi; the rotation speeds of the polishing head and the polishing platen are 93 / 87 rpm, the flow rate of the polishing solution is 300 mL / min, and the polishing time is 2 min. Perform one-step polishing of metallic copper (first polish at high pressure for 1 min and then polish at low pressure for 1 min). According to the real-time thickness change of the copper wafer during the polishing process and combined with a metal film thickness gauge, the polishing rate of the copper wafer under different pressure conditions can be calculated, as shown in Table 2 below: Table 2: Copper Polishing Rates Using the Copper Chemical Mechanical Polishing Solutions of Comparative Examples and Examples

[0050] Generally, under high pressure, the polishing rate of copper is required to be greater than 6000 Å / min, and under low pressure, the polishing rate of copper is required to be in the range of 1500 - 2200 Å / min. Since the two benzotriazole groups in the corrosion inhibitor used in the copper chemical mechanical polishing solution of the present invention are connected by a methylene group or an ethylene group, the copper polishing rate under high pressure can be controlled above 6000 Å / min, even above 6500 Å / min; and the copper polishing rate under low pressure can be controlled within the range of 1500 - 2200 Å / min. In addition, the addition of n-butanol in Examples 3 and 4 changes the polarity of the solvent and the force acting on the corrosion inhibitor, resulting in a significant increase in the copper removal rate during high-pressure polishing. Comparing Example 2 with Example 1, the high-pressure polishing rate of Example 2 is faster, and the low-pressure polishing rates are not much different, indicating that the extension of the flexible chain can further increase the high-pressure polishing rate, thereby improving efficiency and saving time.

[0051] The copper chemical mechanical polishing liquid of Comparative Example 1 uses benzotriazole as a corrosion inhibitor, which has an excessively high copper polishing rate under low pressure. For the corrosion inhibitors used in Comparative Example 3 and Comparative Example 2, the two benzene rings are directly connected. Under high pressure, more benzotriazole groups are adsorbed on the surface of copper, resulting in an excessively low copper polishing rate; under low pressure, fewer benzotriazole groups are adsorbed on the surface of copper, resulting in an excessively high copper polishing rate. In addition, due to the addition of n-butanol in Comparative Example 3, since the two benzotriazole groups of the corrosion inhibitor are directly connected by a single bond and the molecular rigidity is strong, the influence of the corrosion inhibitor by n-butanol is quite different from that of the examples. Compared with the case of Comparative Example 2 without n-butanol, the copper removal rate under high pressure is further reduced. In order to compare the stabilities of the chemical mechanical polishing liquids, the following experiments were conducted: The components are as shown in the following table, and each part is by mass. Stir and mix all components evenly, and adjust the pH value to 6 with 10% potassium hydroxide aqueous solution. Then, seal and shield the obtained chemical mechanical polishing liquid from light, and store it at 5 - 10 °C. After 21 days, Example 5 turns dark yellow and turbid, and a stable and uniform suspension cannot be obtained when stirred again. Example 6 is light yellow in color, and a stable and uniform suspension is obtained after stirring again. According to the method of Example 2, an oxidant is added for polishing, and the effect is basically the same as that of Example 2.

[0052]

[0053] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the method of the present invention, several improvements and supplements can be made, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A chemical mechanical polishing liquid, comprising abrasive grains at a mass percentage of 0.5% to 3%, a corrosion inhibitor at 0.01% - 3%, a complexing agent at 1% to 20%, a surfactant at 0.005% - 3%, a pH regulator, and an oxidant at 0.1% to 1%, with the balance being a solvent; The corrosion inhibitor is selected from one compound or a mixture of multiple compounds in the formula (I) compound; ； In formula (I), R1 - R4 are independently selected from hydrogen, C1 - C12 alkyl groups, and C6 - C20 aryl groups; L is selected from C1 - C6 alkylene groups.

2. The chemical mechanical polishing liquid according to claim 1, wherein R1 - R4 are independently selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, phenyl, naphthyl, biphenyl; L is selected from -(CH2) n -, and n is 1, 2, 3, 4, 5 or 6.

3. The chemical mechanical polishing liquid according to claim 1, wherein The formula (I) compound is selected from: 、 、 、 、 。 4. The chemical mechanical polishing liquid according to claim 1, wherein, The solvent includes water, or a mixture of water and an organic solvent.

5. A formula (I) compound: ； In formula (I), R1 - R4 are independently selected from hydrogen, C1 - C12 alkyl groups, and C6 - C20 aryl groups; L is selected from C1 - C6 alkylene groups; Provided that the compound is not .

6. The compound of formula (I) according to claim 5, wherein, The compound is selected from: 、 、 、 。 7. Use of the compound of formula (I) in the field of chemical mechanical polishing, characterized in that, The formula (I) compound is: ； In formula (I), R1 - R4 are independently selected from hydrogen, C1 - C12 alkyl groups, and C6 - C20 aryl groups; L is selected from C1 - C6 alkylene groups.

8. The application of the chemical mechanical polishing liquid according to any one of claims 1 - 4 in the field of chemical mechanical polishing.

9. A copper polishing method, comprising the following steps: (1) Using the chemical mechanical polishing liquid according to any one of claims 1 - 4, sequentially removing copper on the substrate surface under high pressure and low pressure conditions and stopping on the barrier layer; (2) Removing the barrier layer, a part of the dielectric layer, and a small amount of metallic copper with a barrier layer polishing liquid.

10. The polishing method according to claim 9, characterized in that, The high pressure condition is 1.5 to 2.0 psi, and the low pressure condition is 0.5 to 1.0 psi.

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