Novel electroplating cobalt additive and application thereof in electroplating cobalt

Abstract

The invention provides a novel cobalt electroplating additive and application thereof in cobalt electroplating, and belongs to the technical field of electroplating, and the electroplating process comprises the following steps: preparing an electroplating solution: weighing cobalt sulfate heptahydrate, cobalt chloride hexahydrate and boric acid, dissolving the materials in deionized water, fully stirring until the materials are uniform, then adding the novel cobalt electroplating additive, and uniformly stirring to obtain the electroplating solution; the final electroplating liquid is obtained; carrying out pretreatment on the blind hole electroplating plate; treating the cobalt anode plate; and the electroplating process comprises the steps that a treated blind hole electroplating plate serves as a cathode, a cobalt plate serves as an anode, the cathode and the anode are put into the electroplating liquid prepared in the step (1) together, a power source is switched on, the current and the electroplating time are set, and the electroplating process is completed. According to the novel electroplating cobalt additive, through precise regulation and control of cobalt deposition kinetics, the over-deposition phenomenon at an opening is remarkably inhibited, and the occurrence rate of shrinkage cavity defects is synchronously reduced, so that the uniformity and reliability of an interconnection structure are improved.

Description

Technical Field

[0001] The present invention relates to the field of electroplating technology, and particularly to a novel electroplating cobalt additive and its application in electroplating cobalt. Background Art

[0002] As semiconductor processes continue to scale down to 7 nm and below technology nodes, the integrated circuit interconnect structure faces severe challenges. In the traditional copper interconnect system, the resistivity increases exponentially due to the size effect, exacerbating the RC delay and severely restricting the improvement of chip performance. Therefore, developing alternative interconnect materials with a shorter electron mean free path has become an urgent need in the semiconductor technology industry.

[0003] As a candidate material for the next-generation interconnect technology, metallic cobalt has attracted great attention in the industry due to its unique physical properties. Cobalt has a short electron mean free path and excellent electromigration resistance. Moreover, the cobalt interconnect system has good compatibility with the current copper damascene process, and a smooth process transition can be achieved by optimizing the electrochemical deposition parameters. This characteristic makes it an ideal candidate for the metallization scheme at 7 nm and below nodes.

[0004] During the electro-deposition formation of cobalt interconnects, mass transfer limitations and uneven electric field distribution result in a higher deposition rate at the micropore openings than at the bottom and sidewalls, which easily causes filling defects. These defects will lead to serious interconnect reliability problems. To achieve defect-free filling, it is crucial to use organic additives containing specific functional groups to regulate the cobalt deposition process.

[0005] Under the above technical background, the present invention proposes a compound containing three functional groups as an electroplating cobalt additive. Summary of the Invention

[0006] To solve the above technical problems, the present invention proposes a novel electroplating cobalt additive and its application in electroplating cobalt. The novel electroplating cobalt additive of the present invention precisely regulates the cobalt deposition kinetics, significantly inhibits the over-deposition phenomenon at the openings, and simultaneously reduces the occurrence rate of shrinkage defects, so as to improve the uniformity and reliability of the interconnect structure.

[0007] The technical solution of the present invention is as follows:

[0008] A novel electroplating cobalt additive, comprising a compound containing three functional groups, wherein the compound containing three functional groups is 3-ethynylaniline hydrochloride, and the structural formula of the 3-ethynylaniline hydrochloride is as follows:

[0009]

[0010] The application of the above novel electroplating cobalt additive in electroplating cobalt includes the following steps:

[0011] (1) Preparation of electroplating solution: Weigh cobalt sulfate heptahydrate, cobalt chloride hexahydrate and boric acid, dissolve them in deionized water and stir well until homogeneous, then add a novel cobalt electroplating additive to obtain the final electroplating solution;

[0012] (2) Pretreatment of blind via electroplated board: Use ethanol to degrease the blind via electroplated board, immerse the degreased electroplated board in sulfuric acid solution, take it out and rinse with ethanol, then thoroughly wash with deionized water;

[0013] (3) Treatment of cobalt anode plate: Polish the cobalt anode plate with sandpapers of different grits until the surface is smooth and flat, then immerse it in sulfuric acid solution, take it out and rinse with ethanol, and then wash it with deionized water;

[0014] (4) Electroplating process: Place the treated blind via electroplated board as the cathode and the cobalt plate as the anode together into the electroplating solution prepared in step (1), connect the power supply, and set the current and electroplating time to complete the electroplating process.

[0015] Among them, the novel cobalt electroplating additive is a compound containing three functional groups.

[0016] Among them, the compound containing three functional groups is 3-ethynylaniline hydrochloride.

[0017] Among them, in step (1), the concentration of cobalt sulfate heptahydrate in the prepared electroplating solution is 80 g / L - 100 g / L, the concentration of cobalt chloride hexahydrate is 10 g / L - 30 g / L, the concentration of boric acid is 30 g / L - 50 g / L, and the concentration of the novel cobalt electroplating additive is 5 mg / L - 20 mg / L.

[0018] Among them, the blind hole size of the blind via electroplated board is: the hole diameter is 100 μm - 120 μm, and the hole depth is 80 μm - 125 μm.

[0019] Compared with the prior art, the beneficial effects of the present invention:

[0020] The present invention applies 3-ethynylaniline hydrochloride as a novel small molecule additive to the cobalt electroplating process. The specific steps are as follows: First, weigh a certain weight of cobalt sulfate heptahydrate, cobalt chloride hexahydrate, and boric acid, dissolve them in deionized water and stir well until homogeneous to obtain a basic plating solution, then add a certain concentration of additive (3-ethynylaniline hydrochloride) to obtain the final electroplating solution; place the electroplating solution in an electroplating tank, place the pretreated electroplated board and cobalt anode plate in the electroplating solution as the cathode and anode respectively, connect the power supply, set the current and electroplating time, and complete the electroplating.

[0021] The 3-ethynylaniline hydrochloride provided by the present invention is used as a novel inhibitor throughout the electroplating cobalt process. The provided novel inhibitor is inexpensive and has high environmental friendliness. It is chemically stable during the electroplating cobalt process and is not easily decomposed. Applying the novel electroplating cobalt additive 3-ethynylaniline hydrochloride provided by the present invention to the electroplating cobalt via hole filling process can achieve defect-free filling of blind holes with different depth-to-width ratios. After electroplating, blind hole electroplating cobalt filling without gaps and voids can be obtained, and the surface of the coating is bright and flat, ensuring excellent stability and reliability of the electroplated layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 It is a schematic atomic force microscope (AFM) morphology diagram of the cobalt coating deposited on the surface of the electroplated board in Example 1 of the present invention;

[0024] Figure 2 It is a schematic atomic force microscope (AFM) morphology diagram of the cobalt coating deposited on the surface of the electroplated board in Comparative Example 1 of the present invention;

[0025] Figure 3 It is a schematic cross-sectional metallographic diagram of the blind hole of the electroplated board with the electroplating cobalt solution additive in Example 1 of the present invention;

[0026] Figure 4 It is a schematic cross-sectional metallographic diagram of the blind hole of the electroplated board with the electroplating cobalt solution additive in Comparative Example 1 of the present invention;

[0027] Figure 5 It is a schematic cross-sectional metallographic diagram of the blind hole of the electroplated board with the electroplating cobalt solution additive in Example 2 of the present invention;

[0028] Figure 6 It is a schematic cross-sectional metallographic diagram of the blind hole of the electroplated board with the electroplating cobalt solution additive in Comparative Example 2 of the present invention;

[0029] Figure 7 It is the highest occupied molecular orbital (HOMO) diagram of the novel electroplating cobalt additive 3-ethynylaniline hydrochloride used in Examples 1-2 of the present invention;

[0030] Figure 8 It is the lowest unoccupied molecular orbital (LUMO) diagram of the novel electroplating cobalt additive 3-ethynylaniline hydrochloride used in Examples 1-2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] The terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art, unless otherwise specified.

[0033] In the following embodiments, those not described in detail can be achieved by using conventional experimental means in the art.

[0034] The reagents used in the following embodiments are all commercially available products, and the experimental operations and experimental conditions not specified refer to the conventional operations and conventional conditions in the art.

[0035] In the following embodiments, 3-ethynylaniline hydrochloride is used as a novel cobalt electroplating additive in the process of cobalt electroplating.

[0036] According to the frontier molecular orbital theory, the highest occupied molecular orbital energy (E HOMO ) and the lowest unoccupied molecular orbital energy (E LUMO ) of the 3-ethynylaniline hydrochloride molecule respectively indicate the electron acceptance and donation abilities of the molecule. The energy gap value ΔE = E LUMO - E HOMO , that is, the difference between E LUMO and E HOMO , is an index to measure the adsorption strength of the molecule at the cobalt interface. The smaller the value, the stronger the adsorption ability of the molecule at the interface, and the more significant the inhibitory effect on the electroreduction of cobalt ions. A low value of E LUMO means that the molecule is more inclined to accept electrons from the donor, while a high value of E HOMO indicates that the molecule is more inclined to provide electrons to the acceptor. As shown in Table 1 for quantum chemical calculations, the energy gap ΔE of 3-ethynylaniline hydrochloride is 3.51 eV. This result shows that 3-ethynylaniline hydrochloride has a strong adsorption ability on the cobalt surface, thus effectively inhibiting the reduction process of cobalt ions.

[0037] Table 1 Quantum chemical calculation results of 3-ethynylaniline hydrochloride molecule

[0038]

[0039] The highest occupied molecular orbital (HOMO) diagram and the lowest unoccupied molecular orbital (LUMO) diagram of the novel cobalt electroplating additive 3-ethynylaniline hydrochloride used in the present invention are as shown in Figure 7 and Figure 8as shown

[0040] Example 1

[0041] This example provides an application of a small molecule compound of 3-ethynylaniline hydrochloride as an additive in an electroplating cobalt solution in the electroplating cobalt process, and this process includes the following steps:

[0042] (1) Preparation of the cobalt electroplating solution, and the specific process is as follows:

[0043] Take 80 g of cobalt sulfate heptahydrate, 10 g of cobalt chloride hexahydrate and 30 g of boric acid and dissolve them in 800 mL of deionized water. After stirring until uniform, make up the volume to 1 L with deionized water to obtain 1 L of the basic electroplating cobalt solution. Place the basic electroplating solution in an electroplating bath, and then add 20 mg / L of the electroplating cobalt additive to obtain an electroplating cobalt solution containing the additive;

[0044] (2) Pretreatment of the blind via electroplated board, and the specific process is as follows:

[0045] Immerse the electroplated board in ethanol for 3 min to remove the contaminants on the surface of the electroplated board, rinse it thoroughly with deionized water, then immerse the electroplated board in a 1 mol / L dilute sulfuric acid solution for 2 min to remove the oxides on the surface of the cobalt layer, then immerse the electroplated board in ethanol to remove the contaminants and then rinse it thoroughly with deionized water, and finally blow it dry with an ear syringe. Stick the electroplated board on the front of the stainless steel plate with conductive glue, and then seal the four sides with insulating tape;

[0046] (3) Treatment of the cobalt anode plate, and the specific process is as follows:

[0047] Polish the cobalt anode plate with sandpapers of different particle sizes until the surface is smooth and flat, then put the cobalt anode plate into a 1 mol / L dilute sulfuric acid solution and soak it for 1 min to remove various oxides on the surface of the cobalt plate, then rinse the cobalt plate with ethanol for 1 min to remove the contaminants on the surface of the anode plate, and then rinse it with deionized water for 1 min to obtain a pretreated anode plate;

[0048] (4) Electroplating process: Use the pretreated electroplated board as the cathode and the cobalt anode plate as the anode and put them into the electroplating solution, connect the power supply to complete the electroplating, and the specific process is: Pour the prepared electroplating solution into the electroplating bath, use the pretreated electroplated board as the cathode and the cobalt plate as the anode and put them into the electrolytic cell, connect the positive pole of the DC power supply to the cobalt plate and the negative pole to the electroplated board, turn on the air pump to continuously pass an air flow for stable stirring. For an electroplated board with a blind via size of 120 μm in aperture and 80 μm in depth, electroplating is completed after 4 h of power-on, and the current density is 1 A / dm 2 , and the electroplating result is as Figure 3 .

[0049] Example 2:

[0050] This embodiment provides a small molecule compound of 3-ethynylaniline hydrochloride as an additive for electroplating cobalt solution and its application in the electroplating cobalt process.

[0051] The preparation of the cobalt electroplating solution is as follows:

[0052] Take 100 g of cobalt sulfate heptahydrate, 30 g of cobalt chloride hexahydrate and 50 g of boric acid and dissolve them in 800 mL of deionized water. After stirring evenly, make up the volume to 1 L with deionized water to obtain 1 L of the basic electroplating cobalt solution. Place the basic electroplating solution in the electroplating tank, and then add 5 mg / L of the electroplating cobalt additive to obtain the electroplating cobalt solution containing the additive.

[0053] Compared with Example 1, the difference is that for the electroplating plate with blind holes having a hole diameter of 100 μm and a hole depth of 125 μm, electroplating is completed after 7 h of power-on, and the electroplating results are as Figure 5 .

[0054] From Figure 1 , 3 , and 5, it can be seen that when using 3-ethynylaniline hydrochloride as a new electroplating cobalt additive, after electroplating for a certain period of time with an appropriate concentration of the additive, super filling without holes and gaps can be achieved for blind holes with different depth-to-width ratios, and the cobalt layer on the surface of the coating is uniform and flat.

[0055] Comparative Example 1:

[0056] This embodiment provides a small molecule compound of 3-ethynylaniline hydrochloride as an additive for electroplating cobalt solution and its application in the electroplating cobalt process. Compared with Example 1, the difference is that the new electroplating cobalt additive (3-ethynylaniline hydrochloride) is not added to the blind hole electroplating cobalt solution, and the electroplating results are as Figure 4 .

[0057] Comparative Example 2:

[0058] This embodiment provides a small molecule compound of 3-ethynylaniline hydrochloride as an additive for electroplating cobalt solution and its application in the electroplating cobalt process. Compared with Example 1, the difference is that the new electroplating cobalt additive (3-ethynylaniline hydrochloride) is not added to the blind hole electroplating cobalt solution, and the electroplating results are as Figure 6 .

[0059] As Figure 2 , 4 and 6 show, for the electroplating plate electroplated in the electroplating solution without adding the new electroplating cobalt additive (3-ethynylaniline hydrochloride), it can be found that the filling effect of the blind holes is poor, and the surface of the cobalt layer appears very rough. Compared with Figure 1 , 3From the comparison in Item 5, it can be seen that when the novel electroplating cobalt additive 3-ethynylaniline hydrochloride is added as an inhibitor, seamless void filling can be achieved in blind holes, and the surface of the cobalt deposit is smoother. It can be shown that 3-ethynylaniline hydrochloride as a novel additive can improve the surface morphology of the cobalt coating and achieve super filling of blind holes, making the coating have excellent stability and reliability.

[0060] The above content aims to provide detailed illustrative examples for professionals in related fields to ensure that they can accurately understand and apply the present invention. Based on the prior art, any improvement or adjustment to the present invention obtained by professionals through means such as logical analysis, reasoning, or simple enumeration without creative work shall be deemed to fall within the protection scope defined by the claims of the present invention.

Claims

1. A novel electroplating cobalt additive, characterized in that: It contains a compound with three functional groups, and the compound with three functional groups is 3-ethynylaniline hydrochloride.

2. Use of the novel cobalt electroplating additive according to claim 1 in cobalt electroplating, characterized in that It includes the following steps: (1) Prepare the electroplating solution: Weigh cobalt sulfate heptahydrate, cobalt chloride hexahydrate and boric acid, dissolve them in deionized water and stir well until uniform, and then add a novel cobalt electroplating additive to obtain the final electroplating solution; (2) Pretreat the blind via electroplated board: Use ethanol to degrease the blind via electroplated board, immerse the degreased electroplated board in a sulfuric acid solution, take it out and rinse it with ethanol, and then thoroughly clean it with deionized water; (3) Treat the cobalt anode plate: Polish the cobalt anode plate with sandpapers of different particle sizes until the surface is smooth and flat, then immerse it in a sulfuric acid solution, take it out and rinse it with ethanol, and then wash it with deionized water; (4) Electroplating process: Put the treated blind via electroplated board as the cathode and the cobalt plate as the anode together into the electroplating solution prepared in step (1), connect the power supply, and set the current and electroplating time to complete the electroplating process.

3. The application according to claim 2, wherein: The novel cobalt electroplating additive is a compound containing three functional groups.

4. The application according to claim 3, wherein: The compound containing three functional groups is 3-ethynylaniline hydrochloride.

5. The application according to claim 2, wherein: In step (1), the concentration of cobalt sulfate heptahydrate in the prepared electroplating solution is 80 g / L - 100 g / L, the concentration of cobalt chloride hexahydrate is 10 g / L - 30 g / L, the concentration of boric acid is 30 g / L - 50 g / L, and the concentration of the novel cobalt electroplating additive is 5 mg / L - 20 mg / L.

6. The application according to claim 2, characterized in that: The blind hole size of the blind via test board is: the hole diameter is 100 μm - 120 μm, and the hole depth is 80 μm - 125 μm.

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