A post-chemical mechanical polishing cleaning agent for chips, a preparation method and use thereof

Abstract

This invention relates to a cleaning agent for post-chemical mechanical polishing of chips, comprising the following components by weight: 1-10 parts of functional agent; 0.1-0.5 parts of corrosion inhibitor; 1-5 parts of additive; 1-10 parts of amide; and 80-90 parts of ultrapure water. The invention also discloses the preparation method and uses of this cleaning agent. This invention utilizes the strong chelating ability of the functional agent to remove copper ions, and leverages the preferential adsorption characteristics of the corrosion inhibitor to form a protective film on the copper surface, inhibiting the corrosion of the copper surface by the cleaning agent. The combined use of these two components effectively removes copper oxide without corroding the copper surface. Furthermore, the benzyloxycarbonyl group in the additive protects the amine groups in the functional agent from damage, ensuring the stable existence of the protective film on the copper surface.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing processes, and particularly relates to a cleaning agent for chip chemical mechanical polishing, its preparation method and uses. Background Technology

[0002] Currently, as the feature size of semiconductor device designs becomes smaller and smaller, copper has been widely used for interconnects in semiconductor components. In the traditional multilayer copper interconnect process, the main steps for fabricating one layer of copper interconnect are: depositing a copper thin film in the trench, then performing chemical mechanical polishing (CMP), cleaning after polishing, and finally depositing a barrier layer / dielectric layer to prepare for the fabrication of the next layer of copper interconnect.

[0003] Although the CMP and other steps mentioned above are performed in a clean room, many contaminant particles remain on the surface of the chip after the CMP process. These particles come from the polishing slurry, polishing pad, and the copper particles that are polished off. The Cu and CuO contaminant particles can have a significant impact on the chip, causing electrical connections between two copper wires that should not be conductive, thus resulting in a short circuit.

[0004] Furthermore, copper has two unique properties: firstly, it readily oxidizes into CuO in O2-containing environments; secondly, pure copper is hydrophilic, allowing it to be completely wetted by water, forming a water film. In the next cleaning step, with the high-speed rotating chip surface wetted by pure water, when the cleaning brush approaches, the brush slides on the water film without direct contact with the chip surface. Only the thin film of pure water moves rapidly across the chip surface, removing contaminant particles through friction. However, once the copper surface is oxidized to CuO, it becomes hydrophobic and cannot form a water film. Cleaning with a brush at this point forces the brush into direct contact with the chip surface, causing particles originally attached to the brush to re-adhere to the chip surface, resulting in secondary contamination.

[0005] The drawbacks of existing technologies are primarily that the cleaning agents not only remove CuO but also corrode Cu wires, resulting in a rough surface. This imposes strict limitations on cleaning temperature, concentration, and time; cleaning time is typically limited to tens of seconds to tens of minutes. Furthermore, the subsequent deposition step cannot proceed immediately, necessitating placing the chip in an O2-containing environment while awaiting the next deposition step. For these reasons, the chip can only be placed in an O2-containing environment for a maximum of four hours. This means the production conditions for the next deposition step must be prepared within four hours. Regardless of the reason, exceeding four hours will result in the chip surface being oxidized, forming a CuO film exceeding the thickness limit. Depositing a barrier layer on this CuO film will cause devastating damage to the IC device, as CuO increases circuit impedance or causes open circuits between metal layers, sometimes even forcing the chip to be scrapped. This situation causes significant inconvenience to production and drastically affects the yield rate.

[0006] In summary, if CuO can be removed as soon as possible after the copper CMP step, the waiting time between the copper CMP step and the subsequent barrier layer deposition step can be shortened, which will greatly facilitate production. Summary of the Invention

[0007] The technical problem solved by this invention is that CuO cannot be removed quickly after the copper chemical mechanical polishing (CMP) step, resulting in an excessively long waiting time between the copper CMP step and the subsequent barrier layer deposition step.

[0008] In view of the technical problems existing in the prior art, the present invention designs a cleaning agent for chip chemical mechanical polishing, its preparation method and its uses.

[0009] To solve the aforementioned technical problems, the present invention adopts the following solution:

[0010] A cleaning agent for post-chemical mechanical polishing of chips, characterized in that it comprises the following components by weight:

[0011] Functional agent 1-10 parts;

[0012] Corrosion inhibitor 0.1-0.5 parts;

[0013] 1-5 parts of additives;

[0014] 1-10 parts of amide;

[0015] 80-90 parts ultrapure water;

[0016] The functional agent is a quinoxaline derivative;

[0017] The corrosion inhibitor is a p-hydroxyacetophenone derivative;

[0018] The additive is an L-proline derivative.

[0019] Furthermore, the functional agent is one or more of 6-hydroxyquinoxaline, 2-bromoquinoxaline, 2-(4-bromophenyl)quinoxaline, 4-quinoxaline-2-yl-aniline, and 2-(2'-quinoxaline)-4,4,5,5-tetramethylimidazoline-3-oxy-1-oxy radical.

[0020] Furthermore, the functional agent is a 2-(2'-quinoxalinyl)-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxy free radical, which has the following structure:

[0021] .

[0022] Furthermore, the corrosion inhibitor is one or more of 3'-chloromethyl-4'-hydroxyacetophenone, 4-benzyloxy-3-nitroacetophenone, and 1-{4-(acetoxy)-3-[(acetoxy)methyl]phenyl}acetophenone.

[0023] Furthermore, the additive is one or more of N-acetyl-L-proline, N-(2,4-dinitrophenyl)-L-proline, N-[3-(acetylmercapto)-(2S)-methylpropionyl]-L-proline, and N-benzyloxycarbonyl-L-proline.

[0024] Furthermore, the amide is one or more of formamide, acetamide, propionamide, butyramide, and isobutyramide.

[0025] Furthermore, the corrosion inhibitor is 1-{4-(acetoxy)-3-[(acetoxy)methyl]phenyl}acetone;

[0026] The additive is N-benzyloxycarbonyl-L-proline;

[0027] The amide is isobutyramide.

[0028] This invention also discloses a method for preparing a cleaning agent after chemical mechanical polishing of a chip, characterized by comprising the following steps:

[0029] Step 1: Weigh out the respective amounts of each component;

[0030] Step 2: Add the functional agent, amide, additive, corrosion inhibitor and ultrapure water to the container in sequence, then seal it and treat it with 80KHz ultrasound at 25-50℃ for 0.5-1h until it is completely dissolved, thus obtaining the chip chemical mechanical polishing cleaning agent.

[0031] This invention also discloses a cleaning method for a chip after chemical mechanical polishing using a cleaning agent, characterized by comprising the following steps:

[0032] Step 1: Prepare the chip chemical mechanical polishing cleaning agent into an aqueous solution with a mass percentage concentration of 10-30% using ultrapure water. Then, use this aqueous solution to immerse the semiconductor chip at 25-50℃ for 2-15 hours to obtain the immersed semiconductor chip.

[0033] Step 2: Rinse the soaked semiconductor chip in ultrapure water at least twice to complete the cleaning process of the semiconductor chip.

[0034] This invention also discloses the use of a post-chemical mechanical polishing cleaning agent for semiconductor chip cleaning.

[0035] In this invention, to further improve the cleaning effect, the functional agent is preferably 2-9 parts; the corrosion inhibitor is preferably 0.15-0.45 parts; the additive is preferably 2-4 parts; and the amide is preferably 2-10 parts.

[0036] In this invention, regarding the cleaning method, the prepared chip chemical mechanical polishing cleaning agent is mixed with ultrapure water to form an aqueous solution with a mass percentage concentration of 10-30%. This concentration can be any concentration within the range of 10-30%, such as 10%, 12%, 15%, 18%, 20%, 25%, 28%, 30%, etc. The immersion temperature of the semiconductor chip can be any temperature within the range of 25-50℃, such as 25℃, 30℃, 35℃, 38℃, 40℃, 45℃, 50℃, etc. The immersion time can be any time within the range of 2-15 hours, such as 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 15 hours, etc. The above proportions do not affect the cleaning effect.

[0037] The inventors discovered that quinoxaline has two heterocyclic nitrogen atoms that readily coordinate with metal ions. In order to further enhance the chelation ability with metals, 2-(2'-quinoxalinyl)-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxy radical was synthesized by substituting quinoxaline with oxy radical. The electronegativity of the oxy radical was used to attract positively charged Cu ions.

[0038] More specifically, in the unique structure of this functional agent, the electronegativity of the oxygen radical attracts positively charged Cu ions. Furthermore, the heterocyclic nitrogen atom, which readily coordinates with metal ions, "pulls" the attracted Cu ions from the other side through the force of its lone pair electrons. The combined force of these two forces firmly binds the Cu ions between the two forces. When a large number of functional agent molecules are present in the system of this invention, the spatial structure of the derivative changes, forming a cage-like structure that better confines the Cu ions within it. The formation and presence of this structure allows Cu ions in solution to be better encapsulated within the special macromolecular functional agent, making it easier to remove Cu ions through washing.

[0039] The inventors discovered that the presence of acetoxy groups can rapidly interact electronically with hydroxyl groups on the chip surface, forming a protective film on the chip surface to prevent further oxide layer formation.

[0040] In this invention, the corrosion inhibitor and the hydroxyl groups on the chip surface undergo an electronic effect, which is equivalent to the movement of the substance towards the copper layer surface in the system, and the reaction with the surface occurs.

[0041] At this time, the negatively charged oxygen free radicals in the functional agent repel the hydroxyl groups on the chip surface, preventing the functional agent from moving towards the chip. This can be understood as the functional agent moving away from the direction of the corrosion inhibitor. Therefore, copper ions in the system are more easily cleaned and removed under the coating of the functional agent.

[0042] The inventors have discovered that the presence of amino acid structures in the additive can increase the solubility of the functional agent in solution. The carbonyl groups in the additive can assist the functional agent in improving its coordination properties, further enhancing its ability to encapsulate copper ions. Consequently, copper ions in the system are more easily washed away under the encapsulation of the functional agent.

[0043] It should be noted that, in this invention, unless otherwise specified, the specific meaning of "comprising" in relation to composition definition and description includes both open-ended meanings such as "comprising," "including," etc., and closed-ended meanings such as "composed of," etc., and similar meanings.

[0044] This invention provides a cleaning agent for chip chemical mechanical polishing, its preparation method and uses have the following beneficial effects:

[0045] (1) The present invention uses a specific functional agent, which utilizes the electronegativity of oxygen free radicals to generate electrostatic interaction with positively charged Cu ions to form a special structure, rapidly complexing copper ions and effectively encapsulating them in the middle of a special macromolecular functional agent, making it easier to remove them by washing.

[0046] (2) The functional agent and corrosion inhibitor of the present invention are used at the same time. While removing the metal oxides on the chip surface, a protective film is formed on the chip surface through the interaction of electron donation and electron absorption of the corrosion inhibitor and the hydroxyl groups on the chip surface, which can prevent the chip from being oxidized further.

[0047] (3) The additives in this invention are similar to and compatible with the functional agents due to the presence of their amino acid structure, which greatly increases the solubility of the functional agents.

[0048] (4) This invention utilizes the strong chelating ability of functional agents to remove copper ions, and utilizes the preferential adsorption characteristics of corrosion inhibitors to form a protective film on the copper surface, inhibiting the corrosion of the copper surface by the cleaning agent. The combined use of the two effectively removes copper oxide without corroding the copper surface.

[0049] (5) The benzyloxycarbonyl group in the additive of the present invention can also protect the amine group in the functional agent from being destroyed, so as to ensure the stable existence of the protective film on the copper surface. Attached Figure Description

[0050] Figure 1 : A microscope image of a Cu wafer before cleaning, magnified 50 times;

[0051] Figure 2 : A microscope image of a Cu wafer after cleaning with the cleaning agent of Example 1 of the present invention, magnified 50 times;

[0052] Figure 3 : A microscope image of a Cu wafer cleaned using the cleaning agent of Comparative Example 1 of this invention, magnified 50 times.

[0053] Figure 4 : A microscope image of a Cu wafer cleaned using the cleaning agent of Comparative Example 2 of this invention, magnified 50 times. Detailed Implementation

[0054] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0055] Table 1 Examples

[0056]

[0057]

[0058] Table 2 Comparative Examples

[0059]

[0060] The preparation method of the cleaning agent for the chip after chemical mechanical polishing of the present invention includes the following steps:

[0061] Step 1: Weigh out the respective amounts of each component;

[0062] Step 2: Add the functional agent, amide, additive, corrosion inhibitor and ultrapure water to the container in sequence, then seal it and use 80KHz ultrasound at 30°C for 0.6 hours until completely dissolved to obtain the chip chemical mechanical polishing cleaning agent.

[0063] Cleaning methods for chips after chemical mechanical polishing (CMP).

[0064] It includes the following steps:

[0065] Examples 1-5 are cleaned according to the following method:

[0066] Step 1: Prepare a 20% (w / w) aqueous solution of the chip chemical mechanical polishing cleaning agent with ultrapure water. Then, use this aqueous solution to immerse the semiconductor chip at 30°C for 3 hours to obtain the immersed semiconductor chip.

[0067] Step 2: Rinse the soaked semiconductor chip in ultrapure water at least twice to complete the cleaning process of the semiconductor chip.

[0068] The cleaning method used in the comparative example was performed in accordance with the method described in the embodiment.

[0069] Regarding performance testing and explanation:

[0070] The test method for performance 1 cleaning effect is as follows:

[0071] After CMP, a large number of metal ions and CuO precipitated during the CMP process remain on the Cu wafer. The wafer is cleaned using the cleaning agents of the above-described embodiments and comparative examples of the present invention. The cleaning method includes the following steps:

[0072] Step 1: Prepare a 20% (w / w) aqueous solution of the chip chemical mechanical polishing cleaning agent with ultrapure water. Then, use this aqueous solution to immerse the wafer at 30°C for 3 hours to obtain the immersed wafer.

[0073] Step 2: Rinse the soaked wafers three times in ultrapure water to complete the wafer cleaning process.

[0074] The ultrapure water used in steps 1 and 2 is deionized water with a resistance of at least 18 MΩ.

[0075] The test method for performance 2, electrochemical impedance, is as follows:

[0076] The removal effect of different cleaning agents on CuO was tested using an electrochemical method. The specific test method is as follows:

[0077] A copper electrode (3 mm in diameter) was used as the electrochemical working electrode, platinum as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode. The cleaning agents used in the examples and comparative examples were employed as the electrolyte solution.

[0078] The open-circuit potential-time (OCP-t) curve, dynamic potential polarization curve (Tafel), and impedance were measured for the working electrode. The OCP-t scan range was -0.4V to 0.4V, and the scan time was 1200s. The Tafel curve scan range was OCP ± 0.4V, and the scan rate was 0.01V / s. The corrosion potential was calculated after processing the dynamic potential polarization curve.

[0079] Table 3 Test Results

[0080]

[0081] Analysis and explanation of the test results:

[0082] The copper electrode was immersed to remove the surface oxide layer. The resistance of the pure copper surface was measured to be about 2500Ω using an electrochemical workstation. This means that the CuO was completely removed.

[0083] As can be seen from the test data in Table 3, the corrosion potential values ​​show that the Cu wafers cleaned with the cleaning agent of Comparative Example 1 (which does not contain functional agents) have a very high corrosion potential of (-90) to (-80) mV and an impedance of 5500-6000 Ω, indicating that CuO has not been removed.

[0084] Although the corrosion potential and impedance of the Cu wafer after cleaning with the cleaning agent in Comparative Example 2 (which does not contain corrosion inhibitors) were lower than those in Comparative Example 1, the impedance was still higher than 2500Ω, indicating that CuO was not completely removed.

[0085] The Cu wafers cleaned with the cleaning agent prepared in Example 2 of this invention have a corrosion potential of (-200)-(-190)mV and an impedance of 2200-2500Ω, indicating that CuO has been removed.

[0086] The Cu wafers cleaned with the cleaning agent prepared in Example 1 of this invention showed a corrosion potential decrease to (-240)-(-230) mV and an impedance of 2000-2100 Ω, indicating that CuO was completely removed.

[0087] The condition of the cleaning agent after cleaning, as well as the values ​​of corrosion potential and impedance after cleaning, as shown in the embodiments of the present invention, indicate that CuO can be removed cleanly and the cleaning effect is excellent.

[0088] Further comparison can be made using the accompanying diagrams in the instruction manual:

[0089] Figure 1 This is a microscope image of a Cu wafer before cleaning, magnified 50 times. Figure 2 : A microscope image of a Cu wafer after cleaning with the cleaning agent of Example 1 of the present invention, magnified 50 times.

[0090] from Figure 1 and Figure 2 The comparison shows that the Cu wafer surface cleaned with the cleaning agent of Example 1 of the present invention is smooth and free of residue, and the cleaning effect is good.

[0091] Figure 3 This is a microscope image magnified 50 times after a Cu wafer was cleaned using the cleaning agent of Comparative Example 1 of this invention.

[0092] from Figure 3 It can be seen that there are obvious residues on the surface of the Cu wafer after cleaning with the cleaning agent of Comparative Example 1 of the present invention.

[0093] Figure 4 This is a microscope image of a Cu wafer cleaned using the cleaning agent of Comparative Example 2 of this invention, magnified 50 times.

[0094] from Figure 4 It can be seen that the Cu wafer surface after cleaning with the cleaning agent of Comparative Example 2 of the present invention showed obvious interface delamination. This is because the lack of corrosion inhibitor in the composition led to the corrosion of the Cu wafer.

[0095] This invention utilizes the strong chelating ability of an alkaline functional agent to remove copper ions, and leverages the preferential adsorption properties of a corrosion inhibitor to form a protective film on the copper surface, inhibiting the corrosion of the copper surface by the cleaning agent. The combined use of these two components effectively removes copper oxide without corroding the copper surface. Furthermore, the benzyloxycarbonyl group in the additive protects the amine groups in the functional agent from damage, ensuring the stable existence of the protective film on the copper surface.

[0096] The present invention has been described above by way of example with reference to the embodiments and accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A cleaning agent for chip chemical mechanical polishing, characterized in that, Based on parts by weight, it includes the following components: Functional agent 1-10 parts; Corrosion inhibitor 0.1-0.5 parts; 1-5 parts of additives; 1-10 parts of amide; 80-90 parts ultrapure water; The functional agent is one or more of 6-hydroxyquinoxaline, 2-bromoquinoxaline, 2-(4-bromophenyl)quinoxaline, 4-quinoxaline-2-yl-aniline and 2-(2'-quinoxaline)-4,4,5,5-tetramethylimidazoline-3-oxy-1-oxy radical; The corrosion inhibitor is one or more of 3'-chloromethyl-4'-hydroxyacetophenone, 4-benzyloxy-3-nitroacetophenone, and 1-{4-(acetoxy)-3-[(acetoxy)methyl]phenyl}acetophenone; The additive is one or more of N-acetyl-L-proline, N-(2,4-dinitrophenyl)-L-proline, N-[3-(acetylmercapto)-(2S)-methylpropionyl]-L-proline, and N-benzyloxycarbonyl-L-proline.

2. The chip cleaning agent after chemical mechanical polishing according to claim 1, characterized in that: The functional agent is a 2-(2'-quinoxalinyl)-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxy free radical, which has the following structure: 。 3. The chip cleaning agent after chemical mechanical polishing according to claim 1, characterized in that: The amide is one or more of formamide, acetamide, propionamide, butyramide, and isobutyramide.

4. The chip cleaning agent after chemical mechanical polishing according to claim 3, characterized in that: The corrosion inhibitor is 1-{4-(acetoxy)-3-[(acetoxy)methyl]phenyl}acetone; The additive is N-benzyloxycarbonyl-L-proline; The amide is isobutyramide.

5. A method for preparing a chip cleaning agent after chemical mechanical polishing according to any one of claims 1-4, characterized in that... Includes the following steps: Step 1: Weigh out the respective amounts of each component; Step 2: Add the functional agent, amide, additive, corrosion inhibitor and ultrapure water to the container in sequence, then seal it and treat it with 80KHz ultrasound at 25-50℃ for 0.5-1h until it is completely dissolved, thus obtaining the chip chemical mechanical polishing cleaning agent.

6. A cleaning method using a cleaning agent following chemical mechanical polishing of a chip according to any one of claims 1-4, characterized in that... Includes the following steps: Step 1: Prepare the chip chemical mechanical polishing cleaning agent into an aqueous solution with a mass percentage concentration of 10-30% using ultrapure water. Then, use this aqueous solution to immerse the semiconductor chip at 25-50℃ for 2-15 hours to obtain the immersed semiconductor chip. Step 2: Rinse the soaked semiconductor chip in ultrapure water at least twice to complete the cleaning process of the semiconductor chip.

7. The use of the chip chemical mechanical polishing post-cleaning agent according to any one of claims 1-4 in semiconductor chip cleaning.

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