KR20120052470A - Copper plating process - Google Patents

Abstract

PURPOSE: A copper plating method is provided to control the grain size of copper crystal and reduce the resistivity or surface roughness of plated wiring. CONSTITUTION: A copper plating method comprises the steps of: preparing a copper plating solution composition including crosslinked polyamide of 10-50 mL/L, electroplating using the copper plating solution composition at the normal temperature and pressure, with constant voltage of -0.5-1.5 V and constant current density of 2.5-7.5 mA/cm^2.

Description

Copper Plating Method {COPPER PLATING PROCESS}

The present invention relates to a copper plating solution composition for forming a metal wiring of a semiconductor device and a copper plating method using the same, and more particularly, even from very fine line widths of 100 nm or less, from the bottom of trenches and via holes. The present invention relates to a copper plating method that enables a bottom-up fill process and / or a superfill process.

In the semiconductor device, a plurality of wiring grooves (trenches) for connecting the elements and wiring connection holes (via holes or contact holes) for electrically connecting the multilayer wirings are formed. As the conductive material embedded in these wiring grooves and wiring connection holes, aluminum has been used for about 30 years from the 1960s to the mid-1990s. However, in recent years, as the line width becomes smaller to increase the integration density of semiconductor devices, the RC delay due to the high resistivity of aluminum and the signal transmission system of the circuit are not only caused, but also the charge transfer (EM) Due to the low tolerance, a problem of inferior reliability of the wiring occurred. In order to solve this problem, research on copper having a relatively low resistivity as an alternative material for aluminum has been actively conducted.

Although copper (Cu) is more than 30% higher in electrical conductivity than aluminum, it has not been used in semiconductor processes because it diffuses into silicon and destroys the function of the transistor. However, in the 1990s, a technology to prevent diffusion of copper using Ti / TiN and Ta / TaN, that is, a manufacturing technique of a diffusion barrier, was developed, thereby making it possible to replace metal wiring from aluminum to copper. . In addition to the advantage that copper has higher electrical conductivity than aluminum, copper can have up to 10 times better charge transfer, which critically affects the lifespan of semiconductor devices. Currently, copper is mostly used for line processing of microprocessors and memory devices. .

Unlike aluminum, copper cannot be etched dry, so a conventional aluminum wiring process cannot be applied as it is. The copper wiring process etches the insulating material into the desired wiring structure, then fills the copper and exposes the copper wiring by polishing the extra copper layer by chemical mechanical polishing (CMP, chemical mechanical polishing or chemical mechanical planarization). A so-called damascene process is adopted.

As a method of filling copper in the etched wiring structure, PVD, CVD, electroplating, etc. have been studied and utilized. Among them, the electroplating method of plating a metal thin film layer on a substrate using a conductive electrolyte as a plating solution has been researched most actively because the device cost and manufacturing cost are very low, and the large area can be reliably implemented in terms of quality. Copper plated on the wiring structure has higher electrical conductivity, resulting in lower power consumption, lower heat generation, and higher long-term reliability of the device. However, the presence of a gap between grains even with a high particle size results in lower continuity of the grains, resulting in lower electrical conductivity or short circuit. Therefore, electroplated copper must have high grain size and high grain continuity.

Since the particle size of the electroplated copper depends on the physical properties of the substrate and the process variables, much research has been conducted on the plating conditions for controlling the particle size. In particular, a thin film plated with a plating liquid made of only an inorganic electrolyte may adjust material properties by changing plating conditions such as plating voltage, ion concentration of electrolyte, and temperature of electrolyte. However, pure electrolyte alone cannot implement the bottom-up fill process, or super fill process, which is essential for the formation of the wiring structure.

In order to overcome this, attempts have been made to add metal compounds having excellent electrical and mechanical properties by adding organic compounds, commonly called additives, to an electrolyte. Additives have long been known to play an important role in changing grain growth mechanisms and controlling physical properties such as crystal orientation and surface flatness by controlling copper deposition rates, but when used in combination with several types of additives It is only recently discovered that a floor filling process is possible. Organic additives are generally classified into accelerators, planarizers and moderators according to their reactivity with the plating ions and the properties of the plating result.

As the degree of integration of semiconductor devices increases, the size of the pattern decreases and the aspect ratio increases, making it difficult to uniformly fill the via hole or the inside of the trench. For example, when a via hole inlet having a relatively high current density is filled before the inside, a void occurs in the via hole, resulting in an increase in wiring resistance. The planarizer is adsorbed on the wide flat surface and corners outside the pattern to locally suppress the plating / growth of copper. Ultimately, the copper plating film grows from the bottom of the pattern inside the via hole or the trench to fill the via hole or the trench without cavity. Make it work.

As the flattening agent, polymer materials having a large molecular weight are mainly used, but as the size of the pattern is smaller and the aspect ratio is increased, it is increasingly difficult to select a polymer material having a corresponding filling property. In particular, conventionally known polymer materials are mainly limited to filling through holes in printed circuit boards or enhancing the gloss effect of decorative plating. Therefore, there is a limit to applying them to semiconductor circuits requiring a fine pattern of line width of 100 nm or less. have.

The present invention is to solve the above problems of the prior art, a copper plating solution composition capable of bottom-fill plating without defects such as cavities or seams in the copper wiring having a line width of less than 100 nm and copper plating using the same To provide a method.

In another aspect, the present invention is to provide a copper plating solution composition that can adjust the grain size (grain size) of copper crystals and a copper plating method using the same.

The present invention for achieving the above object relates to a copper plating solution composition comprising a crosslinked polyamide as a flattening agent in a copper plating solution composition for forming a metal wiring of a semiconductor device.

According to the present invention, by including the crosslinked polyamide in a specific content range, it is possible to control the size of crystal grains very finely, and to fill the bottom of a semiconductor circuit requiring a fine pattern with a line width of 100 nm or less, and to reduce resistivity. Discovered to complete the present invention.

Copper plating solutions have been developed in various conventional compositions, and basically contain copper salts, sulfuric acid, and chlorine ions, and as an additive, include accelerators, moderators, planarizers, and the like. The present invention is characterized by using a specific amount of crosslinked polyamide as a flattening agent in the copper plating solution according to the prior art, and the matters not specifically described in the present invention include those included in the prior art.

The present invention relates to a copper plating method,

Preparing a copper plating solution composition containing 10 to 50 mL / L of crosslinked polyamide as a flattener;

Electroplating at room temperature and atmospheric pressure using the copper plating solution composition;

It includes.

Hereinafter, the present invention will be described more specifically.

In the present invention, the copper plating solution composition includes 10 to 50 mL / L of crosslinked polyamide with water, copper salt, sulfuric acid, chlorine ions, and a leveling agent.

In the present invention, the copper salt is preferably a copper compound that provides copper ions, and water-soluble copper salts such as alkaline copper cyanide, copper pyrolate, acidic copper fluoride, and copper sulfate. The concentrations of copper salts, sulfuric acid and chlorine ions may also be used for copper plating solutions. Copper ions, 5 to 65 g / L, sulfuric acid, 5 to 200 g / L, chlorine and 10-100 ppm It is preferable that it is a range.

In the present invention, the crosslinked polyamide is a flattening agent, and adjusts the size of the copper grains to have a smooth and fine surface, and in particular, copper plating is possible even at a fine line width of 100 nm or less by using in a range of 10 to 50 mL / L. Do. As the content of the crosslinked polyamide increases, the surface roughness and the specific resistance of the plated thin film are drastically reduced, but when the content exceeds 50 mL / L, the surface roughness and the specific resistance are not reduced any more, so the effect compared to the content used is not increased. If it is less than 10 mL / L, the size of copper grains is increased, the surface roughness is increased, the specific resistance is increased, and it is not suitable for the application of fine line width below 100 nm.

Examples of such crosslinked polyamides include RaluPlate2887 from Raschig GmbH, Germany. Specifically, for example, caprolactam, dicarbonic acid, and polyimine are reacted to prepare a polyamide including an amine group, and thus prepared polyamide. It can be prepared by crosslinking (polyamide) and epichlorohydrin (epichlorohydrin), but is not limited thereto. More preferably, the average molecular weight of the crosslinked polyamide is preferably in the range of 2000 to 3000 g / mol because there is no excellent smoothness and agglomeration phenomenon.

In addition, the copper plating solution composition as needed in the present invention may be used in addition to the additives used in the field as necessary, but is not limited to polyethylene glycol 3.5 ~ 28 mL / L as a accelerator, SPS as an accelerator In the case of containing (Bis- (3-sulfopropyl) -disulfide, disodium salt) 2.5 to 20 mL / L compatibility with the cross-linked polyamide is improved to produce a finer, flat thin film.

When electroplating using the copper plating solution composition in the present invention, plating at a fine line width at room temperature and atmospheric pressure is possible. The plating is preferably performed at a constant voltage of -1.0 V or less and a constant current density of 20 mA / cm 2 or less, for the plating of copper having excellent film quality and low resistivity.

The copper thin film or the copper wiring manufactured by the copper plating method according to the present invention may be applied to a copper wiring for a semiconductor device, and the wiring may be manufactured in the range of 20 to 40 nm particle size of the plated copper.

According to the copper plating method of the present invention, even a wiring structure having a line width of 100 nm or less can be plated without a defect, and the specific resistance and surface roughness of the plated wiring can be greatly reduced by controlling the particle size.

1 is a scanning electron microscope (SEM) photograph showing the particle size and crystal grains of the surface of the coated copper thin film when the concentration of the crosslinked polyamide is 0 mL / L.
Figure 2 is a scanning electron microscope (SEM) photograph showing the particle size and crystal grains of the surface of the coated copper thin film when the concentration of the cross-linked polyamide is 3 mL / L.
Figure 3 is a scanning electron microscope (SEM) photograph showing the particle size and crystal grains of the surface of the coated copper thin film when the concentration of the cross-linked polyamide is 6 mL / L.
4 is a scanning electron microscope (SEM) photograph showing the particle size and grain size of the surface of the plated copper thin film when the concentration of the crosslinked polyamide is 12 mL / L.
5 is a scanning electron microscope (SEM) photograph showing the particle size and grain size of the surface of the plated copper thin film when the concentration of the crosslinked polyamide is 36 mL / L.
FIG. 6 is a scanning electron microscope (SEM) photograph showing the particle size and grain size of the surface of the coated copper thin film when the concentration of the crosslinked polyamide is 48 mL / L. FIG.
FIG. 7 is a scanning electron micrograph showing changes in particle size and roughness of a cross section of a plated copper thin film when the concentration of the crosslinked polyamide is 0 mL / L. FIG.
FIG. 8 is a scanning electron micrograph showing changes in particle size and roughness of a cross section of a plated copper thin film when the concentration of the crosslinked polyamide is 3 mL / L. FIG.
FIG. 9 is a scanning electron micrograph showing changes in particle size and roughness of a cross section of a plated copper thin film when the concentration of the crosslinked polyamide is 6 mL / L. FIG.
FIG. 10 is a scanning electron micrograph showing changes in particle size and roughness of a cross section of a coated copper thin film when the concentration of the crosslinked polyamide is 12 mL / L. FIG.
FIG. 11 is a scanning electron micrograph showing changes in particle size and roughness of a cross section of a plated copper thin film when the concentration of the crosslinked polyamide is 36 mL / L. FIG.
FIG. 12 is a scanning electron micrograph showing changes in particle size and roughness of a cross section of a coated copper thin film when the concentration of the crosslinked polyamide is 48 mL / L. FIG.
13 is an atomic force microscope (AFM) photograph showing the change in roughness of the surface of the coated copper thin film when the concentration of the crosslinked polyamide is 0 mL / L.
14 is an atomic force microscope (AFM) photograph showing the change in roughness of the surface of the coated copper thin film when the concentration of the crosslinked polyamide is 3 mL / L.
15 is an atomic force microscope (AFM) photograph showing the change in roughness of the surface of the coated copper thin film when the concentration of the crosslinked polyamide is 6 mL / L.
16 is an atomic force microscope (AFM) photograph showing the change in roughness of the surface of the coated copper thin film when the concentration of the crosslinked polyamide is 12 mL / L.
FIG. 17 is an atomic force microscope (AFM) photograph showing the change in roughness of the surface of the coated copper thin film when the concentration of the crosslinked polyamide is 36 mL / L.
18 is an atomic force microscope (AFM) photograph showing the change in roughness of the surface of the coated copper thin film when the concentration of the crosslinked polyamide is 48 mL / L.
19 is a graph showing the change of the surface roughness and the specific resistance of the plated copper thin film according to the concentration of the crosslinked polyamide in the plating solution.
20 is an XRD spectrum showing a change in grain size of a plated copper thin film according to the concentration of crosslinked polyamide before heat treatment in a plating solution.
FIG. 21 is an XRD spectrum showing grain size change of a plated copper thin film with concentration of crosslinked polyamide after heat treatment in a plating solution. FIG.
22 is a graph showing changes in particle size in the Cu (111) direction before and after heat treatment obtained by analyzing the spectra of FIGS. 20 and 21.
Fig. 23 is a scanning electron micrograph showing a wiring structure plating result of a line width of 70 nm without crosslinked polyamide in a plating solution.
Fig. 24 is a scanning electron micrograph showing the results of a wiring structure plating result having a line width of 70 nm to which 12 mL / L of crosslinked polyamide was added in a plating solution.
Fig. 25 is a scanning electron micrograph showing the results of wiring structure plating with a line width of 70 nm to which 52 mL / L of crosslinked polyamide was added in a plating solution.

The present invention will be described in more detail with reference to the following Examples. However, these embodiments are merely examples for easily describing the content and scope of the technical idea of the present invention, and thus the technical scope of the present invention is not limited or changed. In addition, it will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the present invention based on these examples.

Preparation Example 1 Preparation of Plating Solution Composition

For preparing the plating solution, copper sulfate was prepared in a concentration of 40 g / L copper sulfate, 10 g / L sulfuric acid, and 50 ppm hydrochloric acid in tertiary distilled water, followed by 12.5 mL of SPS (Bis- (3-sulfopropyl) -disulfide disodium salt). A solution was prepared by adding / L and 7 mL / L of polyethylene glycol. A plating solution was prepared by adding a crosslinked polyamide (RaluPlate2887 from Raschig GmbH) to the solution at a concentration of 0 mL / L.

Preparation Example 2 Preparation of Plating Solution Composition

A plating solution was prepared in the same manner as in Preparation Example 1, except that 3 mL / L of the crosslinked polyamide was used in Preparation Example 1.

Preparation Example 3 Preparation of Plating Solution Composition

A plating solution was prepared in the same manner as in Preparation Example 1, except that 6 mL / L of the crosslinked polyamide was used in Preparation Example 1.

Preparation Example 4 Preparation of Plating Solution Composition

A plating solution was prepared in the same manner as in Preparation Example 1, except that 12 mL / L of the crosslinked polyamide was used in Preparation Example 1.

Preparation Example 5 Preparation of Plating Solution Composition

A plating solution was prepared in the same manner as in Preparation Example 1, except that 36 mL / L of the crosslinked polyamide was used in Preparation Example 1.

Preparation Example 6 Preparation of Plating Solution Composition

A plating solution was prepared in the same manner as in Preparation Example 1, except that 48 mL / L of the cross-linked polyamide was used in Preparation Example 1.

Example 1

Preparation of Copper Thin Films by Electroplating

1) Fabrication of working electrode substrate for copper plating

In order to fabricate the same working electrode as that of the semiconductor device wiring structure, 20 nm thick Ti was deposited on the surface of the Si (100) substrate by E-beam evaporation. It was deposited to form a working electrode.

2) Preparation of Copper Thin Film by Electroplating

Platinum plate as counter electrode and copper electrode substrate prepared in 1) as working electrode were immersed in the plating solution prepared in Preparation Example 4, and applied with a constant current using Potentiostat / Galvanostat (SI 1286, Solatron or VSI, Biologic) plating system. Electroplating (Galvanostatic electrodeposition) was performed. Plating conditions were carried out so as to form a 0.5 μm thick copper thin film by plating for 5 minutes at a constant voltage of 1 V, a current density of 5 mA / ㎠ at room temperature, atmospheric pressure.

[Example 2]

A copper thin film was formed by electroplating in the same manner as in Example 1, except that the plating solution prepared in Preparation Example 5 was used as the plating solution.

[Example 3]

A copper thin film was formed by electroplating in the same manner as in Example 1, except that the plating solution prepared in Preparation Example 6 was used as the plating solution.

Comparative Example 1

A copper thin film was formed by electroplating in the same manner as in Example 1, except that the plating solution prepared in Preparation Example 1 was used as the plating solution.

Comparative Example 2

A copper thin film was formed by electroplating in the same manner as in Example 1, except that the plating solution prepared in Preparation Example 2 was used as the plating solution.

Comparative Example 3

A copper thin film was formed by electroplating in the same manner as in Example 1, except that the plating solution prepared in Preparation Example 3 was used as the plating solution.

Using the copper thin films prepared in Examples 1 to 3 and Comparative Examples 1 to 3, the copper thin film according to the content of the crosslinked polyamide in the plating solution composition was analyzed.

The surface and the cross section of the prepared thin film were observed through a scanning electron microscope (SEM, S-4800, Hitachi) and the results are shown in FIGS. 1 to 12, respectively. 1 to 6 and 7 to 12 are the surface and cross-sectional structure of the plated copper thin film under the condition that the concentration of the crosslinked polyamide from above is 0, 3, 6, 12, 36 and 48 mL / L, respectively. If no cross-linked polyamide is added, the size of the plated particles may be large, nonuniform, and rough. It can be seen that as the concentration of the crosslinked polyamide increases, the particle size decreases and the surface state becomes uniform and smooth. In particular, it was confirmed that the surface is very uniform in the range of 12 mL / L (Fig. 4 and 10), 36 mL / L (Fig. 5 and 11), 48 mL / L (Fig. 6 and 12) of the present invention Can be.

In order to measure the roughness of the surface, the surface of the thin film was 1.0 μm x 1.0 μm with the atomic force microscopy (AFM) (Nanoman with Liquid cell, Veeco) for the samples of Examples 1 to 3 and Comparative Examples 1 to 3. Scan and the results are shown in Figures 13-18. As shown in FIGS. 13 to 18, it was confirmed that the surface roughness decreased from 16.90 nm to 3.34 nm as the crosslinked polyamide concentration was increased. In particular, it can be seen that the surface is very uniform in the scope of the present invention 12 mL / L (Fig. 16), 36 mL / L (Fig. 17), 48 mL / L (Fig. 18).

19 is a graph showing surface roughness values and specific resistance values measured from nuclear microscopes for samples prepared in the range of 0 to 50 mL / L of crosslinked polyamide. As can be seen in FIG. 19, the surface roughness decreased with increasing concentration of the crosslinked polyamide. The specific resistance was drastically decreased by the addition of a small amount of crosslinked polyamide, and the value did not change significantly even if the concentration was further increased.

In order to confirm the crystal structure and particle size before and after the heat treatment of the copper thin film prepared, the sample prepared in the range of 0-50 mL / L of crosslinked polyamide was analyzed by X-ray diffractometer (XRD). The analysis results are shown in FIGS. 20, 21, and 22. As can be seen in Figure 20 it can be seen that the Cu (200) Cu (311) peak increases as the concentration of the crosslinked polyamide before heat treatment increases. As shown in FIG. 21, after the heat treatment, the Cu 311 decreased and the peak 200 increased. FIG. 22 is a graph showing changes in particle size before and after heat treatment obtained by analyzing the spectra of FIGS. 20 and 21. FIG. 22 is a graph showing a change in particle size in a Cu (111) direction with respect to a peak of Cu (111), which is a main crystal direction. . As shown in FIG. 22, it can be seen that the particle size is smaller than the particle size after the heat treatment before the heat treatment.

Example 4 Formation of Actual Wiring Structure by Electroplating

A substrate having a trench structure having a width of 70 nm and a depth of 120 nm was manufactured in the same manner as in Example 1.

Electroplating was performed for 90 seconds using the substrate as the working electrode in the same manner as in Example 1. FIG. 23 is a SEM photograph showing the case where no crosslinked polyamide is added, and FIG. 24 is a SEM photograph when 12 mL / L of the crosslinked polyamide is added. 23 and 24, when the crosslinked polyamide was added, it was confirmed that the wiring structure was well filled without defects such as cavities during plating. In addition, it was confirmed that the cavity was formed when the concentration was 52 mL / L out of the range of FIG. 25.

Claims (6)

Preparing a copper plating solution composition containing 10 to 50 mL / L of crosslinked polyamide as a flattener;
Electroplating without heat treatment at room temperature and pressure using the copper plating solution composition;
Copper plating method comprising a. The method of claim 1,
The electroplating is a copper plating method performed at a constant voltage of -0.5 ~ 1.5 V and a constant current density of 2.5 ~ 7.5 mA / ㎠. The method of claim 1,
The weight average molecular weight of the crosslinked polyamide is 2000 ~ 3000 g / mol copper plating method. The method of claim 1,
The copper plating solution composition is a copper plating method comprising 3.5 ~ 28 mL / L polyethylene glycol as a reducing agent, 2.5 ~ 20 mL / L SPS as an accelerator. Copper wiring for a semiconductor device using the copper plating method of any one of Claims 1-4. 6. The method of claim 5,
The wiring is a copper wiring having a particle size of plating copper of 20 to 40 nm.

Images