Polishing solution for multi-layer copper interconnection barrier layer and preparation method of polishing solution

Abstract

The invention provides a polishing solution for a multi-layer copper interconnection barrier layer and a preparation method thereof, and the polishing solution for the multi-layer copper interconnection barrier layer comprises the following components in percentage by mass: 0.1-30% of a silicon dioxide abrasive, 0.1-5% of a surfactant, 0.1-10% of a composite chelating agent, 0.1-5% of a bactericide and the balance of a solvent, the composite chelating agent is composed of potassium citrate and potassium carbonate; the pH value of the polishing solution for the multi-layer copper interconnection barrier layer is 10-11. Through mutual cooperation of the silicon dioxide grinding material, the surface active agent, the composite chelating agent and the sterilizing agent, by controlling the particle size range of the grinding material and selecting potassium citrate and potassium carbonate compound chelating agent in a specific proportion, control over the polishing rate and the selection ratio of various materials can be achieved in the polishing process; and meanwhile, the method has relatively high defect correction capability and relatively low surface pollutant index.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical mechanical polishing and relates to a polishing liquid for a multi-layer copper interconnection barrier layer and a preparation method thereof. Background Art

[0002] At present, the integration level of VLSI chips has reached billions of components, and the feature size has entered the nanometer level, which requires hundreds of processes in the microelectronics process, especially multi-layer wiring, substrate, dielectric, etc. must undergo chemical mechanical planarization (CMP). VLSI wiring is transforming from traditional aluminum wiring process to copper wiring process. Compared with Al, Cu wiring has the advantages of low resistivity, high resistance to electromigration, and short RC delay time, which enables Cu wiring to replace Al as the interconnect metal in semiconductor manufacturing. However, copper has the characteristics of rapid migration and is easy to diffuse through the dielectric layer, resulting in leakage between adjacent copper metal wires, which in turn leads to failure of device characteristics. Usually, before the deposition of copper, a diffusion barrier layer is first deposited on the dielectric substrate. The barrier layer material widely used in industry is TaN / Ta.

[0003] Typically, chemical mechanical polishing of copper wiring is divided into two steps: first, remove a large amount of copper and stop at the edge of the barrier layer; then remove the residual copper and barrier metal. During the polishing process, it is necessary to achieve a high material removal rate (MRR) and strictly control the surface defects after polishing. A high and low rate difference needs to be formed at the convex and concave parts of the copper, and the removal rate selection ratio of copper and the barrier layer needs to be guaranteed. In addition, when polishing the barrier layer, due to the coexistence of multiple materials such as Cu and tetraethyl orthosilicate (TEOS), the removal rate of each material cannot be well controlled, which will lead to the aggravation of dishing pits and etch pits, affecting the chip's finished product rate and yield.

[0004] CN106244028A discloses an application of an alkaline polishing liquid in inhibiting galvanic corrosion of a copper-tantalum barrier layer. The raw materials of the alkaline polishing liquid are: a polyhydroxy polyamino chelating agent, a pH regulator, abrasive particles and water. The polyhydroxy polyamino chelating agent reduces the potential of copper in the polishing liquid and forms a passivation layer on the tantalum surface, which reduces the potential of tantalum in the polishing liquid to a small extent, thereby achieving the purpose of reducing the potential difference between the two. At the same time, the corrosion current is reduced, and the corrosion rate is controlled, thereby improving the surface roughness of copper after CMP. However, the above-mentioned alkaline polishing liquid cannot regulate the removal rate selectivity of copper and the barrier layer, and after polishing, it has a lower defect correction ability and a higher surface contaminant index.

[0005] In summary, a polishing liquid for a multi-layer copper interconnect barrier layer is provided to solve the problems of removal rate selectivity, metal ion contamination on the product surface, poor product stability and high surface contaminants in the existing copper interconnect barrier layer polishing technology. Summary of the invention

[0006] The purpose of the present invention is to provide a polishing liquid for a multi-layer copper interconnect barrier layer and a preparation method thereof, wherein the polishing liquid for a multi-layer copper interconnect barrier layer can effectively solve the problems of removal rate selectivity, metal ion contamination on the product surface, poor product stability and high surface pollutants during the polishing process of the copper interconnect barrier layer.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] The present invention provides a polishing liquid for a multilayer copper interconnection barrier layer, which comprises the following components in terms of mass percentage: 0.1-30% of silicon dioxide abrasive, 0.1-5% of surfactant, 0.1-10% of composite chelating agent, 0.1-5% of bactericide, and the balance is solvent;

[0009] The composite chelating agent consists of potassium citrate and potassium carbonate;

[0010] The pH value of the polishing liquid for the multi-layer copper interconnect barrier layer is 10-11, for example, it can be 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8 or 10.9, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0011] In the present invention, the mass percentage of the silica abrasive is 0.1-30%, for example, it can be 1%, 5%, 10%, 15%, 20%, 25% or 28%, the mass percentage of the surfactant is 0.1-5%, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, the mass percentage of the composite chelating agent is 0.1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%, the mass percentage of the bactericide is 0.1-5%, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0012] The polishing liquid provided by the present invention, through the mutual coordination of silicon dioxide abrasive, surfactant, composite chelating agent and bactericide, combined with the use of potassium citrate and potassium carbonate composite chelating agent, can realize the control of polishing rate and selectivity of various materials during the polishing process, and at the same time has higher defect correction ability and lower surface pollutant index, which is beneficial to improving the finished product rate and yield of chips.

[0013] It is worth noting that the composite chelating agent is compounded with potassium citrate and potassium carbonate. TEOS has a negative charge on its surface in an alkaline environment, and the surface of the abrasive SiO2 also has a negative charge. According to the principle that like charges repel each other, the repulsion between the abrasive and TEOS, both of which have negative charges on their surfaces, weakens the mechanical action, and the removal rate of TEOS is low. + Its addition weakens the electrostatic repulsion between the abrasive and TEOS, increases the mechanical interaction between the two, and improves the removal rate of TEOS; an oxidant (hydrogen peroxide) must be added to the polishing liquid before use, which reacts with copper to form Cu 2+ ion state, and then the citrate ions and carbonate ions hydrolyzed by the composite chelating agent dechelate Cu 2+ , accelerating the removal of Cu. Therefore, the selection of a composite chelating agent with a specific composition can be used to control the polishing rate selection of different materials, and the rate selectivity is controllable and adjustable.

[0014] As a preferred technical solution of the present invention, the polishing liquid for the multilayer copper interconnect barrier layer includes the following components in mass percentage: 20-30% silica abrasive, 0.1-5% surfactant, 5-10% composite chelating agent, 0.1-2% bactericide, and the balance is solvent.

[0015] In the present invention, by further optimizing the mass proportion of each component, the control of the polishing rate and selectivity of the polishing liquid on various materials during the polishing process is further improved.

[0016] As a preferred technical solution of the present invention, the average particle size of the silica abrasive is 75-90nm, for example, it can be 77nm, 78nm, 80nm, 82nm, 85nm, 86nm or 88nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] In the present invention, the total content of metal ions (excluding potassium ions) contained in the silica abrasive is ≤100 ppm.

[0018] It is worth noting that by controlling the average particle size range of the silica abrasive, not only can scratches and scratches on the material surface during the polishing process be avoided, the requirements for polishing flatness are met, but also a higher polishing efficiency is ensured.

[0019] Preferably, the silica abrasive is a spherical structure.

[0020] As a preferred technical solution of the present invention, the mass ratio of potassium citrate to potassium carbonate is 1:(0.8-1.2), for example, it can be 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1 or 1:1.15, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 1:1.

[0021] It is worth noting that by controlling the mass ratio range of potassium citrate and potassium carbonate, the polishing rate and selectivity of various materials can be more accurately controlled during the polishing process, which is beneficial to improving the finished product rate and yield of the chip.

[0022] As a preferred technical solution of the present invention, the surfactant includes a nonionic surfactant.

[0023] In the present invention, the nonionic surfactant includes but is not limited to: polyoxyethylene sorbitan ester, polyvinyl alcohol, polyoxyethylene fatty alcohol ether, polyacrylamide or polyethylene glycol.

[0024] Preferably, the bactericide comprises Kathon and / or BIT-20.

[0025] Preferably, the solvent comprises water.

[0026] As a preferred technical solution of the present invention, the pH value of the polishing liquid for the multi-layer copper interconnect barrier layer is 10-10.4, for example, it can be 10.1, 10.2 or 10.3, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] Preferably, the polishing liquid for the multi-layer copper interconnect barrier layer further comprises a pH adjuster.

[0028] Preferably, the pH adjuster includes any one of ammonia water, potassium hydroxide or nitric acid, or a combination of at least two of them.

[0029] In a second aspect, the present invention provides a method for preparing a polishing liquid for a multi-layer copper interconnect barrier layer as described in the first aspect, characterized in that the preparation method comprises the following steps:

[0030] (1) mixing a solvent, a surfactant and a complex chelating agent, and performing a first stirring to obtain a first mixed solution;

[0031] (2) mixing the silica abrasive and the first mixed solution obtained in step (1), and performing a second stirring to obtain a second mixed solution;

[0032] (3) mixing the bactericide and the second mixed solution obtained in step (2), performing a third stirring, and then performing double-stage filtration and canning in sequence to obtain the polishing liquid for the multi-layer copper interconnect barrier layer.

[0033] In the present invention, the mixing method in step (1) is: adding the surfactant, potassium citrate and potassium carbonate into water.

[0034] The preparation method provided by the invention is simple to operate, short in time, and suitable for large-scale industrial production.

[0035] As a preferred technical solution of the present invention, step (2) further comprises, after the second stirring, adding a pH adjuster to the mixture until the pH value is 10-11, and stirring the mixture.

[0036] Preferably, the stirring time is 20-40 min, for example, it can be 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 36 min or 38 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] Preferably, the rotation speed of the stirring treatment is 180-220r / min, for example, it can be 185r / min, 190r / min, 195r / min, 200r / min, 205r / min, 210r / min or 215r / min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] As a preferred technical solution of the present invention, the rotation speeds of the first stirring, the second stirring and the third stirring are all 180-220 r / min, for example, 185 r / min, 190 r / min, 195 r / min, 200 r / min, 205 r / min, 210 r / min or 215 r / min, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the second stirring and the third stirring times are both 50-70 min, for example, 52 min, 55 min, 58 min, 60 min, 62 min, 65 min, 66 min or 68 min, but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] As a preferred technical solution of the present invention, the double-stage filtration in step (3) includes a first filtration and a second filtration performed sequentially.

[0041] Preferably, the accuracy of the first filtration is 0.9-1.1 μm, for example, it can be 0.92 μm, 0.95 μm, 0.96 μm, 0.98 μm, 1 μm, 1.02 μm, 1.05 μm, 1.06 μm or 1.08 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the accuracy of the second filtration is 0.4-0.6μm, for example, it can be 0.42μm, 0.45μm, 0.46μm, 0.48μm, 0.5μm, 0.52μm, 0.55μm, 0.58μm or 0.59μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In the present invention, before the polishing operation is performed, an oxidant with a mass percentage of 0.1-2% needs to be added to the polishing liquid, that is, 0.1-2g of the oxidant is added to 100g of the polishing liquid; the oxidant includes hydrogen peroxide.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The polishing liquid for multi-layer copper interconnect barrier layer provided by the present invention can realize the control of polishing rate and selectivity of various materials during the polishing process by combining the mutual coordination of silicon dioxide abrasive, surfactant, composite chelating agent and bactericide, controlling the particle size range of abrasive and selecting a composite chelating agent of potassium citrate and potassium carbonate in a specific ratio, and at the same time has a high defect correction capability and a low surface contaminant index, which is beneficial to improving the finished product rate and yield of chips;

[0046] (2) The polishing liquid for the barrier layer of multi-layer copper interconnect provided by the present invention is composed of silica abrasive, surfactant, composite chelating agent, bactericide and water, which is low in price, simple in composition and excellent in stability; the preparation method is simple to operate, short in time, and suitable for large-scale industrial production. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] In the following examples and comparative examples, the total content of metal ions (excluding potassium ions) contained in the silicon dioxide abrasive is ≤100ppm; the silicon dioxide abrasives are all spherical. According to the pH value of the polishing liquid, select the corresponding ammonia water, potassium hydroxide or nitric acid to adjust to the required pH value. Before using the polishing liquid, add an oxidant (hydrogen peroxide with a mass percentage of 1%, prepared and used immediately) and mix well.

[0049] Example 1

[0050] The present embodiment provides a polishing liquid for a multilayer copper interconnect barrier layer and a preparation method thereof. The polishing liquid for a multilayer copper interconnect barrier layer comprises the following components, measured by mass percentage: 20% of a silicon dioxide abrasive having an average particle size of 80 nm, 3% of a surfactant, 6% of a composite chelating agent, 1% of a bactericide, and the balance being water;

[0051] The composite chelating agent is composed of potassium citrate and potassium carbonate in a mass ratio of 1:1; the surfactant is PEG400; and the bactericide is kason;

[0052] The multi-layer copper interconnect barrier layer polishing liquid further comprises a pH adjuster; the pH value of the multi-layer copper interconnect barrier layer polishing liquid adjusted by the pH adjuster is 10.2;

[0053] The preparation method comprises the following steps:

[0054] (1) adding PEG400, potassium citrate, and potassium carbonate to water in sequence, and performing a first stirring at a speed of 200 r / min to obtain a first mixed solution;

[0055] (2) mixing the silica abrasive and the first mixed solution obtained in step (1), stirring for a second time at a speed of 200 r / min for 60 min, adding a pH adjuster to the mixture until the pH value reaches 10.2, and then stirring for 30 min at a speed of 200 r / min to obtain a second mixed solution;

[0056] (3) Mixing the Kason and the second mixed solution obtained in step (2), performing a third stirring at a speed of 200 r / min for 60 min, and then performing a first filtration with a precision of 1 μm, a second filtration with a precision of 0.5 μm and canning in sequence to obtain the polishing liquid for the multi-layer copper interconnect barrier layer.

[0057] Examples 2-6 and Comparative Examples 1-6

[0058] The mass percentage of each component of the polishing liquid for the multilayer copper interconnect barrier layer, the average particle size range of the silicon dioxide abrasive, the specific composition of the composite chelating agent and the pH value of the polishing liquid were changed, as shown in Table 1. The other conditions were the same as in Example 1.

[0059] Table 1

[0060]

[0061]

[0062] In order to verify the use effect of the polishing liquid for the barrier layer of the multi-layer copper interconnect of the present invention, a polishing experiment was carried out using the polishing liquid obtained in the above embodiment and the comparative example. The specific polishing conditions are as follows: the model of the polishing pad is Fujibo pad; the polishing pressure is 2psi; the rotation speeds of the polishing head and the polishing disk are 98r / min and 90r / min respectively, the polishing liquid flow rate is 320mL / min, and the polishing time is 1min.

[0063] The polishing rates of Cu, Ta and TEOS materials were measured using a dielectric film thickness tester and a four-probe conductivity meter. The results are shown in Table 2.

[0064] Table 2

[0065]

[0066]

[0067] From Table 2, we can see that:

[0068] (1) The polishing liquid for multi-layer copper interconnect barrier layer provided by the present invention can effectively achieve the requirements of polishing rate and selectivity for Cu, Ta and TEOS materials by using the combination of silica abrasive, surfactant, composite chelating agent and bactericide, and potassium citrate and potassium carbonate composite chelating agent;

[0069] (2) By comparing Example 1 with Examples 3-4, it can be seen that the selection of the average particle size of the silicon dioxide abrasive will affect the polishing rates of Cu, Ta and TEOS materials; if the particle size is too low, the effective grinding abrasive particles will decrease, the mechanical friction and shear force will decrease, resulting in a decrease in the copper removal rate, while the removal rates of TEOS and Ta will not change much; if the particle size is too high, the effective grinding abrasive particles will increase, the mechanical friction and shear force will increase, resulting in an increase in the copper removal rate, while the removal rates of TEOS and Ta will not change much;

[0070] (3) By comparing Example 1 with Examples 5-6, it can be seen that the mass ratio of potassium citrate to potassium carbonate will affect the polishing rates of Cu, Ta and TEOS materials; if the proportion of potassium carbonate is too low, the removal rates of Cu, Ta and TEOS materials will increase because the citrate chelates metal ions to form soluble complexes more strongly; if the proportion of potassium carbonate is too high, the removal rates of Cu, Ta and TEOS materials will decrease;

[0071] (4) It can be seen from the comparison between Example 1 and Comparative Examples 1-2 that when the content of the silica abrasive or the composite chelating agent is too high, the metal ions generated during the polishing process are taken away from the wafer surface, so that the polishing process continues, and the polishing rate is too high, and the requirements for the polishing rate and selectivity of Cu, Ta and TEOS materials cannot be achieved;

[0072] (5) By comparing Example 1 with Comparative Examples 3-4, it can be seen that when the composite chelating agent is not prepared with potassium citrate and potassium carbonate, the requirements for the polishing rate and selectivity of Cu, Ta and TEOS materials cannot be achieved;

[0073] (6) From the comparison between Example 1 and Comparative Examples 5-6, it can be seen that the pH range of the polishing solution will affect the polishing rate of Cu and TEOS materials. If the pH value of the polishing solution is higher than 11, the OH in the solution - The increase accelerates the oxidation of the metal surface, making the oxide layer on the copper or tantalum surface gradually dense, hindering the chemical reaction, resulting in a decrease in the removal rate of copper and tantalum. The silicon dioxide material is negatively charged in the alkaline solution, and the repulsive force with the negative charge on the TEOS surface increases, and the mechanical action weakens, resulting in a decrease in the removal rate of TEOS; if the pH value of the polishing solution is lower than 10, the removal rate of Cu, Ta and TEOS materials will increase.

[0074] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0075] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0076] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0077] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A polishing liquid for a multi-layer copper interconnect barrier layer, characterized in that: The polishing liquid for the multi-layer copper interconnect barrier layer comprises the following components in percentage by mass: 0.1-30% of silicon dioxide abrasive, 0.1-5% of surfactant, 0.1-10% of composite chelating agent, 0.1-5% of bactericide, and the balance is solvent; The composite chelating agent consists of potassium citrate and potassium carbonate; The pH value of the polishing liquid for the multi-layer copper interconnect barrier layer is 10-11.

2. The polishing liquid for multi-layer copper interconnect barrier layer according to claim 1, characterized in that: The polishing liquid for the multi-layer copper interconnection barrier layer comprises the following components in percentage by mass: 20-30% of silicon dioxide abrasive, 0.1-5% of surfactant, 5-10% of composite chelating agent, 0.1-2% of bactericide, and the balance is solvent.

3. The polishing liquid for multi-layer copper interconnect barrier layer according to claim 1 or 2, characterized in that: The average particle size of the silica abrasive is 75-90nm; Preferably, the silica abrasive is a spherical structure.

4. The polishing liquid for a multi-layer copper interconnect barrier layer according to any one of claims 1 to 3, characterized in that: The mass ratio of the potassium citrate to potassium carbonate is 1:(0.8-1.2).

5. The polishing liquid for a multi-layer copper interconnect barrier layer according to any one of claims 1 to 4, characterized in that: The surfactant includes a nonionic surfactant; Preferably, the bactericide comprises Kathon and / or BIT-20; Preferably, the solvent comprises water.

6. The polishing liquid for a multi-layer copper interconnect barrier layer according to any one of claims 1 to 5, characterized in that: The pH value of the polishing liquid for the multi-layer copper interconnect barrier layer is 10-10.4; Preferably, the polishing liquid for the multi-layer copper interconnect barrier layer further comprises a pH adjuster; Preferably, the pH adjuster includes any one of ammonia water, potassium hydroxide or nitric acid, or a combination of at least two of them.

7. A method for preparing a polishing liquid for a multi-layer copper interconnect barrier layer according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: (1) mixing a solvent, a surfactant and a complex chelating agent, and performing a first stirring to obtain a first mixed solution; (2) mixing the silica abrasive and the first mixed solution obtained in step (1), and performing a second stirring to obtain a second mixed solution; (3) mixing the bactericide and the second mixed solution obtained in step (2), performing a third stirring, and then performing double-stage filtration and canning in sequence to obtain the polishing liquid for the multi-layer copper interconnect barrier layer.

8. The preparation method according to claim 7, characterized in that: Step (2) after the second stirring, further comprises: adding a pH adjuster to the mixture until the pH value is 10-11, and stirring; Preferably, the stirring time is 20-40 min; Preferably, the rotation speed of the stirring process is 180-220 r / min.

9. The preparation method according to claim 7 or 8, characterized in that: The rotation speeds of the first stirring, the second stirring and the third stirring are all 180-220 r / min; Preferably, the second stirring and the third stirring are both performed for 50-70 min.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The double-stage filtration in step (3) includes a first filtration and a second filtration performed sequentially; Preferably, the precision of the first filtration is 0.9-1.1 μm; Preferably, the second filtration has an accuracy of 0.4-0.6 μm.

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