KR20070067813A - New leveler for leveling and cu electro deposition by using the same - Google Patents

Abstract

A leveling agent capable of performing superconformal deposition without fine defects on a trench with various aspect ratios and providing a flat copper thin film without a step height difference, a copper electroplating solution comprising the leveling agent, and a copper electroplating method using the copper electroplating solution are provided. A quarternary ammonium bromide leveling agent has an alcohol functional group used in copper electroplating. The leveling agent is benzyl-di-(3-hydroxypropyl)-methyl ammonium bromide. A copper electroplating solution comprises a quarternary ammonium bromide leveling agent having an alcohol functional group used in copper electroplating. The copper electroplating solution comprises: a basic copper electroplating solution including 40 g/L of copper(Cu), 10 g/L of sulfuric acid(H2SO4) and 50 ppm of chlorine ions(Cl^-); additives including 13.68 mg/L of bis(3-sulfopropyl)disulfide(SPS) as an accelerant and 2 ml/L of an Enthone VS solution as an inhibitor; and 20 mg/L of the prepared leveling agent. A copper electroplating method comprises performing an electrodeposition process using the copper electroplating solution comprising a quarternary ammonium bromide leveling agent having an alcohol functional group used in copper electroplating.

Description

New leveling agent for leveling flatness and copper electroplating method using same {NEW LEVELER FOR LEVELING AND CU ELECTRO DEPOSITION BY USING THE SAME}

FIG. 1 is an SEM image showing the elemental electrodeposition of trenches having various aspect ratios 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 cross-sectional view showing the ¹ H-NMR results of benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide which is Compound (II) prepared in Example 1 of the present invention.

4 is a graph showing the electrodeposition tendency according to the concentration of benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide which is Compound (II) prepared in Example 1 of the present invention.

FIG. 5 is a graph showing a competitive adsorption curve with an accelerator (SPS) according to the concentration of benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide, which is Compound (II) prepared in Example 1 of the present invention.

6 is a SEM photograph of the copper thin film prepared in Example 2 of the present invention.

The present invention relates to a novel planarizer for step smoothing in copper electroplating, and a copper electroplating method using the same. More specifically, trenches having various aspect ratios make an elementary electrodeposition without microdefects and have no step difference. The present invention relates to a planarizer capable of providing a flat copper thin film and a copper electroplating method using the same.

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.

Copper electroplating is a thin film formation method that enables elemental electrodeposition via a combination of additives of accelerators and inhibitors. Accelerators are substances which adsorb on the surface of copper to accelerate the reduction of copper ions. Among accelerators of sulfonate-based compounds, materials having thiol (-SH) and disulfide (SS) functional groups are well known as accelerators. Inhibitors also adsorb on the copper surface but form a blocking layer to prevent the reduction reaction to prevent copper reduction. At present, the most widely used additives to achieve elemental electrodeposition are inhibitors, a combination of polyethylene glycol (PEG) and chloride ions (Cl ⁻ ), and an accelerator as bis (3-sulfopropyl) disulfide (bis ( 3-sulfopropyl) disulfide) (SPS). FIG. 1 illustrates a trench having various aspect ratios prepared by a bottom-up filling process manufactured by a conventional copper electroplating method using a copper electroplating solution including the additives (accelerator and inhibitor). An isometric picture is shown.

The combination of PEG-Cl ^- SPS in copper electroplating is most commonly used because it shows excellent ability for 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 aggregate becomes larger because the density of the bumps increases 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 time of the process in the chemical mechanical polishing process and causes device defects because of low uniformity of residual thickness.

In order to solve such a problem, research is being conducted to prevent the formation of steps. U.S. Pat.Nos. 6,679,973, 6,610,192, 6,350,364, and 0,249,177A1 disclose techniques for preventing the formation of steps using planar agents. In addition, US Pat. No. 6,653,226 discloses a step planarization process using 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 flattening agent is formed flat without any step on the front side after the end of the deposition regardless of the size and density of the trench.

As the flattening agent, a material having a large molecular weight or a functional group having a heteroatom such as nitrogen, oxygen, or sulfur as a polymer is registered in the patent. Among them, planarizers having an amine (Nitrogen) functional group are widely used. Specifically, pyridine or a ring structured amine functional group has been proposed.

In the present invention, a flatter having quaternary ammonium bromide, which is one of the important functional groups of the cationic surfactant, and also having an alcohol (alcohol) functional group was synthesized, and the performance of the flattener was verified through electrodeposition experiments.

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a quaternary ammonium bromide flattener having an alcohol functional group, which is a novel flattener for leveling.

In addition, an object of the present invention is to provide a copper electroplating solution comprising a planar having a variety of aspect ratios can provide a flat copper thin film without the difference of the elementary electrodeposition and microscopic defects.

In addition, an object of the present invention is to provide a copper electroplating method using a copper electroplating solution containing the flattening agent.

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 provides a quaternary ammonium bromide flattener having an alcohol functional group used for copper electroplating.

In another aspect, the present invention provides a copper electrolytic plating solution containing the flattening agent and a copper electrolytic plating method using the copper electrolytic plating solution.

Hereinafter, the present invention will be described in detail.

(a) Benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide leveler

Leveling agents of the present invention are quaternary ammonium bromide levelers with alcohol functionality, in particular benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide levelers.

The benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide flattening agent was selected from benzyl-methyl-amine (((C ₆ H ₅ ) CH ₂ ) (CH ₃ ) NH) and a base as shown in Scheme 1 below. Using potassium carbonate (K ₂ CO ₃ ), 3-bromopropanol (BrCH ₂ CH ₂ CH ₂ OH) is added to carry out the substitution reaction, and the substituted reactant is filtered, extracted, washed and dried. Compound (I) may be prepared through a synthesis process purified by column chromatography.

Scheme 1

Compound (I) prepared above was subjected to a substitution reaction by adding 3-bromopropanol (BrCH ₂ CH ₂ CH ₂ OH) again at room temperature, and the substituted reaction product was filtered, extracted, washed and dried and then purified. It can be manufactured from compound (II).

Compound (II) prepared above may be included in the copper electrolytic plating solution to shorten the time for flattener development by examining the tendency before being used in the electrodeposition process.

In order to evaluate the inhibitory role of the compound (II), the concentration of electrodeposition can be analyzed. Equipment for the analysis may be ECI Technology, QUALILAB QL-10, Cyclic Voltammetric Stripping (CVS), and Virgin Make-up Solution (VMS) is 40 g / L copper (Cu), 10 g / L sulfuric acid ( H ₂ SO ₄ ), 50 ppm chlorine ion (Cl ⁻ ) may be used. The electrodeposition tendency analysis is to analyze the effect on the electrodeposition in the generalized concentration range of the prepared compound (II), the concentration range analyzed is the concentration range in which additives (flatner, accelerator, inhibitor) are generalized (0 to 80 μM), the reaction test (Response Test) can be analyzed by the analysis framework.

In addition, the compound (II) can be analyzed by preparing a solution containing the same molar accelerator and the compound (II) in order to evaluate the degree of superiority in the competitive adsorption of the promoter and the metal surface. If the promoter shows an advantage in competitive adsorption, it will show an acceleration curve; if compound (II) shows an advantage, it shows an inhibition curve.

In analyzing the tendency of the compound (II), it is preferable to normalize the dependent variable of the reaction curve.

The electrodeposition tendency analysis according to the concentration and the evaluation of the degree of superiority in the competitive adsorption of the promoter and the metal surface can confirm that the prepared compound (II) has a tendency as a flat agent.

(b) copper electroplating solution

The copper electrolytic plating solution of the present invention is a copper electrolytic plating solution containing the prepared flat agent.

The copper electrolytic plating solution is a bis (accelerator as an additive to a basic copper electrolytic plating solution containing 40 g / L of copper (Cu), 10 g / L of sulfuric acid (H ₂ SO ₄ ) and 50 ppm of chloride ions (Cl ⁻ )). 3-sulfopropyl) disulfide (SPS) 13.68 mg / L, an inhibitor of Enthone VS solution 2 mL / L and 20 mg / L of the leveling agent prepared above.

The basic copper electrolytic plating solution preferably has a pH of 0.5 to 1.5.

The accelerator may be used as an accelerator solution containing 98% by weight of sulfuric acid diluted with 228 mg of bis (3-sulfopropyl) disulfide (SPS) and 0.99 mL of sulfuric acid in 100 mL of distilled water.

(c) copper electroplating method

Copper electroplating method of the present invention using a copper electroplating solution containing benzyl ^- di- (3-hydroxypropyl) -methyl ammonium bromide, which is the flattener prepared as described above, It is a copper electroplating method that produces a planar copper thin film at the same time as the elementary electrodeposition through a combination.

The copper electroplating method

Performing an electrodeposition process on the specimen with the copper electrolytic plating solution; and

Washing the electrodeposited specimen with ultrapure water for 1 to 5 seconds and removing water with nitrogen gas;

It is made, including.

The electrodeposition process may be performed by applying a current of 3 to 6 mA / cm ² compared to SCE (Standard Calomel Electrode).

The electrodeposition time of the electrodeposition process is affected by the pattern size, preferably 5 to 100 seconds.

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

(a) Preparation of benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide leveler

Add benzyl-methyl-amine (((C ₆ H ₅ ) CH ₂ ) (CH ₃ ) NH) and 1.5 equivalents of potassium carbonate (K ₂ CO ₃ ) as a base, to which 3-bromopropanol (BrCH ₂ CH Substitution reaction was performed by adding 1.5 equivalents of ₂ CH ₂ OH). The reaction was stirred at room temperature for 6 hours and then filtered using a filter paper. The filtered solution was extracted using distilled water. The organic solvent used here was dichloromethylene (CH ₂ Cl ₂ ). The extracted organic solvent layer was washed with saturated sodium chloride (NaCl) solution, and water was removed using magnesium sulfate (MgSO ₄ ). Then, Compound (I) was obtained by purification by column chromatography in a developing solution mixed with CH ₂ Cl ₂ : CH ₃ OH = 98: 2.

To the compound (I) obtained above, 3-bromopropanol (BrCH ₂ CH ₂ CH ₂ OH) was further added at room temperature to perform a substitution reaction, and stirred for about 1 hour to obtain a salt. The salt was filtered using acetone (CH ₃ C (O) CH ₃ ) from which water was removed, and once again, the salt was dissolved in acetone (CH ₃ C (O) CH ₃ ) and filtered to obtain a compound. (II) was obtained. ¹ H-NMR of the prepared compound (II) is shown in FIG. 3.

According to FIG. 3, it was confirmed that an ammonium salt was formed by performing a substitution reaction through four proton integral values of chemical shifts 1.729, 3.308, and 3.553 peaks. 400 Hz ¹ H-NMR chemical shift (H integral; Coupling splitting) is 1.726 ppm (4H; m), 2.599 ppm (3H; s), 3.308 ppm (4H; m), 3.553 (4H; t), 4.457 (2H; s), 7.481 (5H; m), m is multiplet, s is singlet, d is doublet, t is triplet.

(b) Trend analysis of benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide flatner

① The electrodeposition tendency of the benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide which is the prepared compound (II) is analyzed and shown in FIG. 4. The concentration range to be analyzed set a range (0 to 80 μM) in which the additive was generalized, and the assay frame was a response test.

4, it can be seen that the synthesis of benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide is reduced by 40% compared to when not added to the electrodeposition process. A _R / A _R 0 is greater than 0.6, where A _R is a voltamogram that is proportional to the electrodeposition amount of the metal at a constant concentration of the additive (benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide) (Voltammogram) stripping area (mC), A _R 0 is the stripping area of Voltagram proportional to the electrodeposition amount of the metal without additive (benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide) It is shown.

② Prepare a solution containing the same moles of benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide and bis (3-sulfopropyl) disulfide (SPS) as an accelerator to promote SPS as a promoter and a metal surface The degree of superiority in adsorption was evaluated and shown in FIG. 5. If SPS, an accelerator, has an advantage in competitive adsorption, it will have an acceleration curve (A _R / A _R 0> 1), while if benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide has an advantage, the inhibition curve ( A _R / A _R 0 <1).

As shown in FIG. 5, the curve of the inhibition tendency showed that the benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide prepared above had an advantage in competitive adsorption on the metal surface. .

From the results of the above ① and ② it was confirmed that the benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide prepared tended as a flat agent.

Example 2

(a) Preparation of Copper Electrolytic Plating Solution Containing Benzyl-di- (3-hydroxypropyl) -methyl Ammonium Bromide Leveler

A basic copper electrolytic plating solution containing 40 g / L of copper (Cu), 10 g / L of sulfuric acid (H ₂ SO ₄ ) and 50 ppm of chloride ion (Cl ⁻ ) was prepared. As an accelerator, 228 mg of bis (3-sulfopropyl) disulfide (SPS) and 0.99 mL of sulfuric acid, which were vacuum dried at 95 ° C., were diluted with 100 mL of distilled water, and used as an accelerator solution.

Basic copper electroplating with 2 mL / L of Enthone OMI VS, 6 mL / L of accelerator solution and 20 mg / L of benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide, which was prepared in Example 1 above Dilute to 1 L of solution to prepare a copper electroplating solution.

(b) copper electroplating

The substrate has an aspect ratio (AR) of 2.5: 1 and a trench width of 180 nm, and the structure is Cu (60 nm) / Ta (7.5 nm) / TaN (7.5 nm) / Si, and the copper Copper electroplating was performed using the electrolytic plating solution (a).

After performing the electrodeposition process for 20 to 100 seconds with the copper electrolytic plating solution prepared in (a), the electrodeposited specimen was washed with ultrapure water for 1 to 5 seconds and dried with nitrogen gas. SEM photographs of the prepared copper thin film are shown in FIG. 6.

Through (a) of FIG. 6, it was confirmed that a reliable copper thin film was prepared by depositing different patterns having various aspect ratios and densities without microdefects, and (b) almost no copper in different patterns. It was confirmed that a thin film was prepared. Through this, it was confirmed that benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide, a compound prepared in Example 1, had a flattening effect as a flattening agent.

As described above, according to the present invention, trenches having various aspect ratios may make an elementary electrodeposition without microdefects and provide a flat copper thin film without a step difference. Further, in demonstrating that quaternary ammonium bromide acts as a leveling agent, and suggesting the possibility that alcohol functional groups may be involved in the leveling action, in developing the leveling agent, the analysis framework through CVS equipment (1) Providing a tendency test for the electrodeposition of the compound and (2) a competitive adsorption test with the accelerator, there is an effect of shortening the time to develop the flattening agent. In addition, there is an effect to provide a single process copper electroplating method using a variety of additives using a quaternary ammonium bromide flattener.

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 (12)

Quaternary ammonium bromide levelers with alcohol functionality used in copper electroplating. The method of claim 1, And said flattener is benzyl-di- (3-hydroxypropyl) -methyl ammonium bromide. A copper electrolytic plating solution comprising the planarizing agent according to claim 1. The method of claim 3, wherein The copper electrolytic plating solution is a bis (accelerator as an additive to a basic copper electrolytic plating solution containing 40 g / L of copper (Cu), 10 g / L of sulfuric acid (H ₂ SO ₄ ) and 50 ppm of chloride ions (Cl ⁻ )). 3-sulfopropyl) disulfide (SPS) 13.68 mg / L, copper electroplating solution, characterized in that it comprises 2 mL / L of the Enthone VS solution as an inhibitor and 20 mg / L of the prepared leveling agent. Electrolytic plating method characterized by electrodeposition with the copper electrolytic plating solution of Claim 3. The method of claim 5, The copper electroplating method Performing an electrodeposition process on the specimen with the copper electrolytic plating solution of claim 3; and Washing the electrodeposited specimen with ultrapure water for 1 to 5 seconds and removing water with nitrogen gas; Copper electroplating method comprising a. The method of claim 5, The copper electroplating method is a copper electroplating method, characterized in that the single step (single step). The method of claim 6, The electrodeposition process is a copper electrolytic plating method, characterized in that made by applying a current of 3 to 6 mA / cm ² compared to SCE (Standard Calomel Electrode). The method of claim 6, The electrodeposition step is a copper electroplating method, characterized in that the electrodeposition time is 5 to 100 seconds. In the method of analyzing the tendency of the planarizing agent of Claim 1, Cyclic Voltammetric Stripping (CVS) is used to analyze the tendency of the planarizer. The method of claim 10, The trend analysis method (1) tendency tests for electrodeposition of compounds and (2) Competitive adsorption test with accelerator The tendency analysis method of the planarizing agent characterized by consisting of. The method of claim 10, The tendency analysis method of copper (Cu) 40 g / L, sulfuric acid _{(H 2 SO 4) 10 g} / L, chloride ion (Cl ^-) is characterized in that analysis by using a plating solution basic copper electrolyte containing 50 ppm Method for analyzing the tendency of the leveling agent.

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