KR20070059617A - Cu electro deposition by using leveler - Google Patents

Abstract

A Cu electrodeposition method which performs conformal deposition and manufactures a Cu thin film free of bumps at the same time by using a Cu electrodeposition solution comprising benzotriazole as a leveler is provided. In a Cu electrodeposition solution having a basic composition comprising copper sulfate, sulfuric acid, polyethylene glycol, sodium chloride, and bis(3-sulfopropyl)disulfide, the Cu electrodeposition solution comprises benzotriazole as a leveler. In a Cu electrodeposition method using a basic composition comprising copper sulfate, sulfuric acid, polyethylene glycol, sodium chloride, and bis(3-sulfopropyl)disulfide, the Cu electrodeposition method comprises performing post-electrodeposition, or pre- and post-electrodeposition using benzotriazole as a leveler. The Cu electrodeposition method comprises the steps of: (i) electrodepositing a substrate for 5 to 50 seconds in a Cu electrodeposition solution prepared by adding polyethylene glycol, sodium chloride, and bis(3-sulfopropyl)disulfide into a basic solution comprising copper sulfate and sulfuric acid; (ii) cleaning the electrodeposited substrate with ultra-pure water for 1 to 5 seconds, and removing water from the substrate using nitrogen gas; (iii) adding benzotriazole into the basic solution, and performing post-electrodeposition of the water-removed substrate for 140 seconds; and (iv) cleaning the post-electrodeposited substrate with ultra-pure water for 5 to 10 seconds, and removing water from the substrate using nitrogen gas.

Description

Metal electroplating method using leveling agent {CU ELECTRO DEPOSITION BY USING LEVELER}

1 is a SEM photograph of a copper thin film formed by a conventional copper electroplating method in a damascene structure.

2 is a cross-sectional view showing the formation of a copper thin film, (a) is a cross-sectional view of a copper thin film electrodeposited by the prior art, and (b) is a cross-sectional view of a copper thin film electrodeposited using a flattening agent.

3 is a SEM photograph of a copper thin film of a substrate prepared using the copper electroplating method (A) of the present invention.

4 is an SEM photograph of a copper thin film of a substrate manufactured using the copper electroplating method (B) of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper electroplating method of a semiconductor wiring process, and more particularly, using a copper electroplating solution containing benzotriazole as a flattener, to suppress bump formation and growth, thereby leveling the entire wafer area. The present invention relates to a copper electroplating method capable of producing a copper thin film.

As semiconductor wiring becomes multi-layered, trenches with high aspect ratios are formed, and thus there is a need for a reliable copper thin film without defects such as voids and seams. It is rising.

The electroplating method for manufacturing such a copper thin film is a thin film formation method that enables superconformal deposition through a combination of an additive of an accelerator and an inhibitor. Accelerators are substances which adsorb on the surface of copper to accelerate the reduction of copper ions. Among the sulfonate-based compounds, materials having mercapto (-SH) and disulfide (S-S) bonds are well known as accelerators. Inhibitors are also substances which adsorb on the copper surface but form a blocking layer to prevent the reduction of copper. At present, additives for forming elementary electrodeposition include inhibitors of polyethylene glycol (PEG) and chlorine ions (Cl-), and accelerators of bis (3-sulfopropyl) disulfide. (SPS) is the most widely used.

The combination of PEG-Cl-SPS, an additive in copper electroplating, is most commonly used because of its excellent effect in conformal electrodeposition. However, bumps are formed under the influence of the accelerator during electrodeposition, and as the bumps grow, one aggregate is formed in the late stage of electrodeposition. The formed aggregates become larger because the densities of the bumps increase in areas where the aspect ratio of the trench is high and the density is higher. This phenomenon is called overplating or overburden. The over-deposited areas form a step with the surrounding area, which increases the process time in the chemical mechanical polishing process and causes a problem of device defects because the uniformity of the residual thickness is low.

In order to solve such a problem, research is being conducted to prevent the formation of steps. US Pat. Nos. 6,679,973, 6,610,192 and 6,350,364 disclose techniques for preventing the formation of steps using levelers. As another technique, US Pat. No. 6,653,226 discloses a step planarization process using an oxidation potential as a technique for changing process conditions.

According to FIG. 2, in the case of the copper thin film (a) electrodeposited according to the prior art without using a flattening agent, a step is formed as the electrodeposition time elapses, and particularly, the area where the dense trenches are gathered forms a larger step. Done. On the other hand, the copper thin film (b) electrodeposited using the planarizer is formed flat without any step on the front side after the electrodeposition is completed regardless of the size and density of the trench.

As a flattening agent for preventing the formation of a step, a patent has been registered for a substance having a specific functional group such as an organic group having a high molecular weight or a high molecular weight and an amino group. However, the flattening agent, which is currently commercialized and most of the materials are registered in the patent, is mostly polymer-based, and thus the use of the flattening agent is limited.

In the present invention, the use of benzotriazole as a leveling agent, to provide a new material in addition to the leveling agent mainly known to date to provide a variety of use of the leveling agent.

In order to solve the problems of the prior art as described above, the present invention uses a copper electroplating solution containing benzotriazole as a flattening agent to achieve an elemental electrodeposition and at the same time a copper electroplating method that can produce a copper thin film without a step The purpose is to provide.

The above and other objects of the present invention can be achieved by the present invention described below.

In order to achieve the above object, the present invention is a copper electrolytic plating solution based on copper sulfate, sulfuric acid, polyethylene glycol, sodium chloride, bis (3-sulfopropyl) disulfide, benzotriazole (BTA) as an additive It provides a copper electrolytic plating solution comprising a as a leveler (leveler).

In addition, the present invention is a copper electrolytic plating method based on copper sulfate, sulfuric acid, polyethylene glycol, sodium chloride, bis (3-sulfopropyl) disulfide, the late electrodeposition or pre-deposition and post-deposition using benzotriazole as a flattening agent It provides a copper electroplating method, characterized in that.

Hereinafter, the present invention will be described in detail.

In the present invention, using a copper electrolytic plating solution containing benzotriazole as a flattening agent in the copper electroplating, the planarization without the step at the same time through the elementary electrodeposition through a combination with PEG-Cl-SPS, which is well known in the conventional process A copper thin film can be manufactured. Originally, benzotriazole has been studied as a brightener for reducing the roughness of copper thin films or as an inhibitor for forming an isotropic electrodeposition in a semiconductor copper electroplating process. In addition, it is widely known as a corrosion inhibitor in chemical mechanical polishing processes. However, in the present invention, by using the PEG-Cl-SPS combination additive as a flattening agent, it shows a very excellent effect as a flattening agent in addition to the role known to date.

The copper electrolytic plating solution of the present invention is a copper electrolytic plating solution having copper sulfate, sulfuric acid, polyethylene glycol, sodium chloride, and bis (3-sulfopropyl) disulfide as a base composition, and comprising benzotriazole as a flattener. Solution.

The copper electroplating method of the present invention is a late electrodeposition or pre and post electrodeposition using benzotriazole as a flattener in copper electroplating based on copper sulfate, sulfuric acid, polyethylene glycol, sodium chloride, bis (3-sulfopropyl) disulfide. It is a copper electroplating method characterized by electrodeposition.

The copper electroplating method

(Iii) electroplating the substrate for 5 to 50 seconds in a copper electrolytic plating solution in which polyethylene glycol, sodium chloride, and bis (3-sulfopropyl) disulfide are added to a basic solution consisting of copper sulfate and sulfuric acid;

(Ii) washing the electrodeposited substrate with ultrapure water for 1 to 5 seconds and removing water with nitrogen gas;

(Iii) adding benzotriazole to the base solution and late electrodepositing the substrate from which the moisture has been removed for 140 seconds; And

(Iii) washing the late electrodeposited substrate with ultrapure water for 5 to 10 seconds and removing water with nitrogen gas;

It is a method (A) which consists of.

In addition, the copper electroplating method

(Iii) electrodepositing the substrate for 5 to 50 seconds in a copper electrolytic plating solution in which polyethylene glycol, sodium chloride, bis (3-sulfopropyl) disulfide and benzotriazole are added to a basic solution consisting of copper sulfate and sulfuric acid;

(Ii) washing the electrodeposited substrate with ultrapure water for 1 to 5 seconds and removing water with nitrogen gas;

(Iii) post-depositing the water-removed substrate with the copper electrolytic plating solution of (iii) for 140 seconds; And

(Iii) washing the late electrodeposited substrate with ultrapure water for 5 to 10 seconds and removing water with nitrogen gas;

It is a method (B) which consists of.

The copper electroplating method is performed by applying a voltage of -250 mV to SCE (Standard Calomel Electride) in a basic solution consisting of copper sulfate and sulfuric acid, and is a multi-step process in which copper electroplating is divided into several steps. Is done.

The copper electroplating method (A) is a copper electrolytic plating solution containing a copper sulfate of 0.25 M, 1 M sulfuric acid, a polyethylene glycol 88 μM, sodium chloride 1 mM, bis (3-sulfopropyl) disulfide 50 μM as an additive Electrodeposition for 5 to 50 seconds, and the late electrodeposition using a copper electrolytic plating solution containing 0.01 to 5 mM of benzotriazole as the leveling agent to the base solution.

The copper electroplating method (B) is a copper electrolytic plating solution comprising copper sulfate and sulfuric acid, including polyethylene glycol and sodium chloride as an additive, and bis (3-sulfopropyl) disulfide as an additive and benzotriazole as a flattening agent. By using a plating solution, the concentration of bis (3-sulfopropyl) disulfide and benzotriazole in each step is changed to produce a defect-free and step-free copper thin film by stepwise electrodeposition.

The copper electroplating method (B) is a basic solution consisting of 0.25 M copper sulfate and 1 M sulfuric acid, 88 μM polyethylene glycol as an additive, 1 mM sodium chloride, 0.01 to 1 mM bis (3-sulfopropyl) disulfide, and benzotria as a flatter. Electrolytic electrodeposition is carried out for 5 to 50 seconds with a copper electrolytic plating solution containing 0.01 to 5 mM of a sol, and late electrodeposition is carried out with a copper electrolytic plating solution having the same configuration as above.

In the electrodeposition step (i) of the copper electrolytic plating method (B), the concentration ratio of bis (3-sulfopropyl) disulfide and benzotriazole is preferably 1: 1 to 1:20, and the ratio is 1: 8 at an optimum concentration ratio. It is more preferable.

In the late electrodeposition step (B) of the copper electrolytic plating method (B), the concentration ratio of bis (3-sulfopropyl) disulfide and benzotriazole is preferably 1: 1 to 1: 200, and the optimal concentration ratio is 1:80. It is more preferable.

In the late electrodeposition of the copper electrolytic plating methods (A) and (B), the electrodeposition time is preferably 140 seconds, which can be controlled by process conditions.

The combination and concentration of the additives in each step of the copper electroplating method are shown in Table 1 below.

Copper Electroplating Method (A) Copper Electroplating Method (B) Electric electrodeposition Late electrodeposition Electric electrodeposition Late electrodeposition Electrodeposition time (s) 5 to 50 140 5 to 50 140 Leveling agent BTA - 0.01 to 5 mM 0.01 to 5 mM 0.01 to 5 mM additive PEG 88 μM - 88 μM 88 μM Cl ^- 1 mM - 1 mM 1 mM SPS 50 μM - 0.01 to 1 mM 0.01 to 1 mM

The substrate has an aspect ratio of 2: 1, a trench width of 160 nm, and has a structure of Cu (60 nm) / Ta (7.5 nm) / TaN (7.5 nm) / Si.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

EXAMPLE

Example 1

Preparation of Copper Thin Film Using Copper Electroplating Method (A)

A substrate having an aspect ratio of 2: 1, a trench width of 160 nm, and having a Cu (60 nm) / Ta (7.5 nm) / TaN (7.5 nm) / Si structure was formed using copper sulfate 0.25 M, sulfuric acid 1 In a basic solution consisting of M, bumps were formed by electro-depositing with a copper electrolytic plating solution for 40 seconds in a PEG-Cl-SPS containing 88 μM polyethylene glycol, 1 mM sodium chloride, and 50 μM bis (3-sulfopropyl) disulfide as an additive. Copper electroplating was performed until now. The electrodeposited substrate was washed with ultrapure water for 5 seconds and dried with nitrogen gas. The water-removed substrate was subjected to late electrodeposition for 140 seconds in a copper electrolytic plating solution in which 200 μM of benzotriazole was added to a basic solution consisting of 0.25 M of copper sulfate and 1 M of sulfuric acid. The late electrodeposited substrate was washed with ultrapure water for 10 seconds and dried with nitrogen gas.

The SEM photograph of the copper thin film after the said electrodeposition process (a) and the late electrodeposition process (b) is shown in FIG.

As a result, the copper thin film produced by the copper electroplating method (A) of the present invention was observed from the bottom (bottom-up precess) during the electrodeposition process, it was confirmed that the bump was formed as evidence. Therefore, it was confirmed that the electrodeposited membrane was free of defects. In addition, it can be seen that in the substrate having the damascene structure, the step difference is much reduced as compared with the copper thin film of FIG. 1 formed by the conventional electrolytic plating method.

Example 2

Preparation of Copper Thin Film Using Copper Electroplating Method (B)

In Example 1, the base solution consisting of 0.25 M copper sulfate and 1 M sulfuric acid, PEG-Cl containing 88 μM polyethylene glycol, 1 mM sodium chloride, 50 μM bis (3-sulfopropyl) disulfide, and 400 μM benzotriazole -Electrodeposited for 40 seconds with -SPS-BTA copper electrolytic plating solution, to a basic solution consisting of 0.25 M copper sulfate, 1 M sulfuric acid, 88 μM polyethylene glycol, 1 mM sodium chloride, 25 μM bis (3-sulfopropyl) disulfide and Example 1 was carried out in the same manner as in Example 1 except for the late electrodeposition for 140 seconds with PEG-Cl-SPS-BTA copper electroplating solution containing 2000 μM of benzotriazole.

The SEM photograph of the copper thin film after the said electrodeposition process (a) and the late electrodeposition process (b) is shown in FIG.

As a result, the copper thin film produced by the copper electroplating method (B) of the present invention, like the copper thin film prepared in Example 1, bottom-up precess was observed in the electrodeposition process and bumps as a proof thereof. It could be confirmed that was formed. In addition, it was confirmed that there is no step difference compared with the copper thin film of FIG. 1 formed by the conventional copper electroplating method.

Comparative Example 1

A substrate having an aspect ratio of 2: 1, a trench width of 160 nm, and having a Cu (60 nm) / Ta (7.5 nm) / TaN (7.5 nm) / Si structure was formed using copper sulfate 0.25 M, sulfuric acid 1 Electrolytic plating was carried out on a basic solution consisting of M, electro-deposited with copper electrolytic plating solution for 180 seconds in PEG-Cl-SPS containing 88 μM polyethylene glycol, 1 mM sodium chloride, and 50 μM bis (3-sulfopropyl) disulfide as an additive. It was.

An SEM photograph of the prepared copper thin film is shown in FIG. 1.

As a result, it was confirmed that a step of about 400 nm or more was formed in a region of high trench density, which indicates the importance of the planarizer in the copper electroplating produced by electrodeposition only with a combination of an accelerator and a moderator.

As described above, according to the present invention, benzotriazole (BTA) is used as a leveler, and copper electroplating is used to perform superconformal deposition, and to suppress bump formation and growth. Since there is no leveling in all areas, there is an effect of manufacturing a copper thin film which can improve the efficiency and improve the yield of the device in the chemical mechanical polishing process.

Although described in detail above with reference to the specific embodiments of the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention, and such variations and modifications belong to the appended claims. It is also natural.

Claims (7)

A copper electrolytic plating solution having copper sulfate, sulfuric acid, polyethylene glycol, sodium chloride, and bis (3-sulfopropyl) disulfide as a base composition, comprising a benzotriazole (BTA) as a flattening agent. solution. In the copper electrolytic plating method which makes copper sulfate, sulfuric acid, polyethyleneglycol, sodium chloride, bis (3-sulfopropyl) disulfide a basic composition, A copper electroplating method characterized by late electrodeposition or pre and late electrodeposition using benzotriazole as a flattening agent. The method of claim 2, The copper electroplating method (Iii) electroplating the substrate for 5 to 50 seconds in a copper electrolytic plating solution in which polyethylene glycol, sodium chloride, and bis (3-sulfopropyl) disulfide are added to a basic solution consisting of copper sulfate and sulfuric acid; (Ii) washing the electrodeposited substrate with ultrapure water for 1 to 5 seconds and removing water with nitrogen gas; (Iii) adding benzotriazole to the base solution and late electrodepositing the substrate from which the moisture has been removed for 140 seconds; And (Iii) washing the late electrodeposited substrate with ultrapure water for 5 to 10 seconds and removing water with nitrogen gas; It is a method (A) which consists of a copper electroplating method characterized by the above-mentioned. The method of claim 2, The copper electroplating method (Iii) electrodepositing the substrate for 5 to 50 seconds in a copper electrolytic plating solution in which polyethylene glycol, sodium chloride, bis (3-sulfopropyl) disulfide and benzotriazole are added to a basic solution consisting of copper sulfate and sulfuric acid; (Ii) washing the electrodeposited substrate with ultrapure water for 1 to 5 seconds and removing water with nitrogen gas; (Iii) post-depositing the water-removed substrate with the copper electrolytic plating solution of (iii) for 140 seconds; And (Iii) washing the late electrodeposited substrate with ultrapure water for 5 to 10 seconds and removing water with nitrogen gas; It is a method (B) which consists of a copper electroplating method characterized by the above-mentioned. The method of claim 3, wherein The copper electroplating method (A) is a copper electrolytic plating solution containing a copper sulfate of 0.25 M, 1 M sulfuric acid, a polyethylene glycol 88 μM, sodium chloride 1 mM, bis (3-sulfopropyl) disulfide 50 μM as an additive Electro-deposition of the copper electroplating method, characterized in that the electro-deposition by using a copper electrolytic plating solution containing 0.01 to 5 mM of benzotriazole as a flat agent to the base solution. The method of claim 4, wherein The copper electroplating method (B) is a basic solution consisting of 0.25 M copper sulfate and 1 M sulfuric acid, 88 μM polyethylene glycol as an additive, 1 mM sodium chloride, 0.01 to 1 mM bis (3-sulfopropyl) disulfide, and benzotria as a flatter. Electrolytic electrodeposition with a copper electrolytic plating solution containing 0.01 to 5 mM of a sol, and late electrodeposition with a copper electrolytic plating solution having the same configuration as above. The method of claim 4, wherein In the copper electroplating method (B), the bis (3-sulfopropyl) disulfide and benzotriazole in the electrodeposition step (v) have a concentration ratio of 1: 1 to 1:20, and the bis (3) in the late electrodeposition step (v). The concentration ratio of sulfopropyl) disulfide and benzotriazole is 1: 1 to 1: 200, characterized in that the copper electroplating method.

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