KR20110095519A - Neutral co-w-p three-element alloys electroless plating solution, electroless plating method using the same and co-w-p three-element alloys coating layer prepared by the same - Google Patents

Abstract

PURPOSE: A neutral Co-W-P three-element alloys electroless plating solution, electroless plating method using the same and Co-W-P three-element alloys coating layer prepared by the same are provided to prevent the environmental contamination generated due to heavy metal. CONSTITUTION: A neutral Co-W-P three-element alloys electroless plating solution comprises metal salt, reducing agent, additive agent and painting agent. The metal salt comprises cobalt acetate or cobalt sulfate, and ammonium tungstate. The reducing agent comprises sodium hypophosphite. The painting agent is composed of citric acid sodium. The pH stabilizer comprises boric acid.

Description

Neutral electroless cobalt-tungsten-phosphorus tri-alloy plating solution, electroless plating process using the same and cobalt-tungsten-phosphorus tri-alloy film prepared thereby same and Co-WP three-element alloys coating layer prepared by the same}

The present invention relates to a neutral electroless cobalt-tungsten-phosphoric tri-alloy plating solution, an electroless plating process using the same, and a cobalt-tungsten-phosphorus tri-alloy film prepared thereby, and more particularly cobalt acetate or cobalt sulfate, tungsten By adding an additive that does not contain heavy metals to a plating solution using ammonium acid as a metal source and sodium hypophosphite as a reducing agent, pits or cracks are reduced, fine grains are formed, and a very dense surface structure is obtained. The present invention relates to a neutral electroless cobalt-tungsten-phosphorus tri-alloy plating solution, an electroless plating process using the same, and a cobalt-tungsten-phosphorus ternary alloy film produced thereby.

The signal transfer speed of the semiconductor chip is generally lowered by a resistance-capacitance delay (RC delay) occurring in the metal wiring. That is, the resistance-capacitance delay caused by the resistance of the wiring and the capacitance of the interlayer insulating film negatively affects the speed of the device to be improved. Although aluminum (Al) has been used as a wiring material for the past 30 years, copper (Cu) has a higher resistance to electromigration than aluminum, which improves the reliability of semiconductor devices. It is emerging as a useful wiring material for integrated circuits because the signal transmission speed can be increased even if it is formed at a small width. In addition, copper has the advantage of low power consumption and inexpensive compared to aluminum. However, copper is a material that is difficult to etch, and thus it is difficult to pattern into a desired wiring shape after deposition. Thus, in 1997, a damascene copper wiring process was used by IBM, which previously formed wiring-shaped grooves with an interlayer insulating film and then filled with copper.

On the other hand, unlike aluminum, which has been used as a wiring material, copper has a low passivation effect due to its own surface oxide film, so that the surface is easily oxidized, and its reactivity with silicon is strong to form silicide. In addition, since the diffusion coefficient of copper in silicon or silicon dioxide is about 100 times larger than that of ordinary metals, a reliable diffusion barrier layer is required to prevent destruction of the semiconductor device by heat treatment.

In general, metals are known to diffuse well at the interface between the metal wiring layer and the diffusion barrier layer in semiconductors, such as the diffusion coefficient at the surface or the interface is much larger than the bulk. Contrary to the expectation that copper has a 1.64 times higher melting point than aluminum, the resistance to EM (Electromigration) is large, and there is no significant difference in the actual wiring. Able to know.

Therefore, in order to apply the damascene copper wiring process to the maximum while solving the reliability problem due to the EM of the wiring material, research on the alternative material of the diffusion barrier layer and a process for forming the diffusion barrier layer using the same is required. Conventionally, a hardmask type diffusion barrier layer, such as SiN or SiCN, is formed by using a conventional plasma coating apparatus. However, the dielectric constant is rather high and the wiring capacitance is high. There was a problem of increasing.

To solve this problem, the wiring resistance of the wiring material can be lowered with lower electrical resistance than that of a hard mask type diffusion barrier such as SiN or SiCN, but the hilllock of the wiring material due to EM or stress migration (SM) can be achieved. As a technique capable of mechanically suppressing the occurrence of, the diffusion barrier layer formed by electroless plating has been studied. Here, electroless plating is a method of plating through a chemical reaction without using electricity, and uses a principle that metal ions included in the plating solution receive electrons and are reduced and adhere to the surface of the object to be plated.

Accordingly, the present inventors have proposed a neutral electroless Co-WP tertiary alloy plating solution that can replace a conventional anti-diffusion capping layer such as SiN or SiCN using an expensive plasma coating equipment, an electroless plating process using the same, and manufactured by the same. Developed Co-WP ternary alloy film. In particular, the neutral electroless Co-WP tertiary alloy plating solution is based on Co having excellent high temperature characteristics, and by adding an additive containing no heavy metal, suppressing the pit of the plated film and miniaturizing the plated particles to diffuse copper diffusion It was confirmed that there is an effect that can be prevented to complete the present invention.

Accordingly, an object of the present invention is to add an additive not containing heavy metal to a plating solution containing cobalt acetate or cobalt sulfate and ammonium tungstate as a metal source, and sodium hypophosphite as a reducing agent, thereby adding: 1) cobalt as a high melting point metal; Tungsten is alloyed to prevent oxidation and diffusion of copper wiring, 2) to form a plating film with excellent thermal stability, and 3) neutral electroless cobalt-tungsten- that does not use environmentally harmful substances such as lead. It is to provide a three-membered alloy plating solution.

It is also an object of the present invention, by using a neutral electroless cobalt-tungsten-phosphorus tri-plating solution, neutral electroless cobalt which can prevent the occurrence of erosion and deformation of the material and thereby secure the renality of the microcircuit It is to provide a tungsten phosphorus ternary alloy plating solution.

In addition, it is an object of the present invention, because it is carried out at a low temperature and a suitable pH range, the plating is fast and effectively plated, but also cobalt and tungsten, which does not easily precipitate in acid, can be more easily precipitated, It is to provide an electroless plating process that can prevent the occurrence of erosion and deformation of the ash.

It is also an object of the present invention to provide a cobalt-tungsten-phosphoric trialloy coating which can reduce pits or cracks, form fine grains and have a very dense surface texture.

As one aspect for achieving the above object, the present invention relates to an electroless cobalt-tungsten-phosphoric terpolymer plating solution comprising cobalt acetate or cobalt sulfate, ammonium tungstate and sodium hypophosphite. The cobalt acetate or cobalt sulfate is used as a metal salt, and any one of them may be optionally included.

At this time, the concentration of the cobalt acetate or the cobalt sulfate is 10 to 20 g / l, the concentration of the ammonium tungstate is 5 to 10 g / l, and the concentration of sodium hypophosphite is 20 to 40 g / l It is preferable.

When the concentration of cobalt acetate or cobalt sulfate is less than 10 g / l, the plating rate is lowered. When the concentration of cobalt acetate or cobalt is more than 20 g / l, the plating rate is increased but decomposition of the plating solution is likely to occur. Similarly, if the concentration of sodium hypophosphite is less than 20 g / l, the plating rate decreases and productivity decreases. If the concentration of sodium hypophosphite exceeds 40 g / l, the plating rate increases, but the stability of the solution decreases, resulting in decomposition of the plating solution. There is an easy disadvantage.

The plating solution is characterized in that the plating solution further comprises sodium citrate as a complexing agent and boric acid as a pH stabilizer.

The complexing agent controls the plating rate and prevents spontaneous decomposition of the plating to provide a composition having excellent solution stability. In particular, the sodium citrate complexing agent which is stable in alkalinity and exhibits good properties of cobalt and tungsten stability and complexability Preferably provided as. In order to maintain the performance as a complexing agent in the plating solution, the concentration of sodium citrate is preferably 20 to 60 g / l.

The pH stabilizer is a material used to maintain the pH of the plating liquid in the plating process, and since the pH is affected by the degree of plating and the thickness of the plating layer, it is preferable to add a material capable of maintaining the pH of the plating liquid. It is preferable that the concentration of boric acid is about 30 g / l in order to maintain the performance as a pH stabilizer within.

On the other hand, the plating solution further comprises an additive, characterized in that the additive does not contain a heavy metal, it is characterized in that selected from the group consisting of ammonium hypophosphite, NaSCN, KSCN and mixtures thereof.

In this case, when ammonium hypophosphite is added as the additive, ammonium hypophosphite is preferably added within a range of 10 to 1000 ppm, and when NaSCN is added as the additive, NaSCN is added within a range of 0.1 to 5.0 ppm. desirable. Preferably, it is more preferred that ammonium hypophosphite in the range of 10 to 1000 ppm and NaSCN in the range of 0.1 to 5.0 ppm are added together.

By adding an additive containing no heavy metal to the plating solution, not only heavy metal contamination and environmental pollution caused by heavy metals are prevented, but also the plated cobalt-tungsten-phosphoric alloy coating reduces pits and cracks, It is finely formed and can have a very dense surface texture.

The pH of the plating liquid is controlled by sodium hydroxide, characterized in that 7.0 to 10.0. When the pH range is 7.0 to 10.0, the plating speed is fast and the plating is effectively performed, and cobalt and tungsten, which are not easily precipitated in acid, can be more easily precipitated. In addition, by using a neutral plating solution, it is possible to prevent the erosion and deformation of the material to occur, and to secure the reliability of microcircuits in various semiconductors and packages and printed circuit boards requiring copper wiring.

On the other hand, ammonium tungstate is characterized in that it is dissolved in sodium hydroxide solution and added in the form of ions. Since ammonium tungstate is not easily dissolved and is not easily plated when added to the plating solution, it is preferable to dissolve it in sodium hydroxide solution first and then add it in ionic form to form an effective plating solution.

This neutral cobalt-tungsten-phosphorus electroless ternary alloy solution forms a dense microstructure in a stable plating solution, improves thermal stability, chemical and mechanical properties, and is added as an alloying element by using an appropriate complexing agent and process conditions. It is possible to provide a plating film layer which suppresses the occurrence of cracking due to internal stress that can be raised by suppressing the pit generated in the plating film through an appropriate additive.

As another aspect of the present invention, the present invention includes plating a metal (eg, copper) using the electroless cobalt-tungsten-phosphorus tri-alloy plating solution described above to form a diffusion barrier layer on the metal surface. The present invention relates to an electroless plating process.

At this time, the electroless plating process is preferably carried out in a temperature range of 60 to 90 ℃ and pH range of 7.0 to 10.0. These process conditions are set to minimize chemical influences such as deformation or erosion on the metal surface on which the alloy coating is to be formed, and more easily to allow the alloy coating to be formed on the metal surface.

In particular, according to the process temperature range, a denser and finer alloy coating structure can be formed at a low temperature. When the temperature is low, it has a low plating rate and has a faster plating rate when the temperature is high.

In addition, according to the process pH range, chemical erosion or corrosion of the device can be suppressed, and cobalt and tungsten, which are not easily precipitated in acid, can be more easily precipitated. And by adjusting the process pH, it is possible to control the amount of vacancy of tungsten or phosphorus vacancy in the plating film.

As still another aspect of the present invention, the present invention relates to a cobalt-tungsten-phosphorus terpolymer coating plated on a metal surface by the electroless cobalt-tungsten-phosphorus tertiary alloy plating solution described above.

According to the present invention, a high melting point metal cobalt and tungsten may be alloyed to form a more reliable and thermally stable plating film, and it is possible to prevent environmental pollution by heavy metals without using environmentally harmful substances such as lead. Neutral electroless cobalt-tungsten-phosphoric tri-alloy plating solution can be provided.

In addition, according to the present invention, since the plating process is carried out at a low temperature and a suitable pH range, the plating is fast and effectively performed, and cobalt and tungsten, which are not easily precipitated in acid, are more easily formed on the copper material. It can be deposited, and there is an effect of minimizing chemical effects such as deformation or erosion on the metal surface on which the alloy film is formed.

In addition, according to the present invention, there is an effect that the amount of vacancy in tungsten or phosphorus vacancy in the plating film can be adjusted according to the plating process or the pH of the plating solution.

In addition, according to the present invention, the cobalt-tungsten-phosphorus tri-alloy film is densely grown without pits or voids to increase the diffusion preventing effect of copper, and fine circuits in various semiconductors, packages, and printed circuit boards requiring copper wiring. There is an effect that can ensure the reliability of.

In addition, according to the present invention, the cobalt-tungsten-phosphorus tri-alloy film prevents an increase in resistance due to oxidation of a copper wiring by a subsequent high temperature process and suppresses EM due to diffusion of copper at an interface.

1 is a photograph of the appearance of the plating film formed by the plating solution prepared by Comparative Production Example 1,
Figure 2 is a photograph of the appearance of the plating film formed by the plating solution prepared by Preparation Example 1 according to the present invention,
3 is a photograph of the appearance of the plating film formed by the plating solution prepared by Preparation Example 2 according to the present invention,
4 is a photograph of an atomic force microscope of a plating film formed by the plating solution prepared in Comparative Preparation Example 1,
5 is a photograph of the atomic force microscope of the plating film formed by the plating solution prepared by Preparation Example 1 according to the present invention,
6 is a photograph of an atomic force microscope of a plating film formed by the plating solution prepared by Preparation Example 2 according to the present invention.

Hereinafter, the content of the present invention will be described in more detail with reference to Examples. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited by these examples.

<Comparative Production Example 1>

A plating solution was prepared by adding 20-40 g / L sodium hypophosphite as a reducing agent to 10-20 g / L cobalt sulfate as a metal source, and mixing 2-20 g / L sodium citrate with a complexing agent. Then, 5-10 g / L ammonium tungstate was dissolved in sodium hydroxide solution and added to the plating solution in the form of ions. In addition, 0.5 ppm of Pb and NaSCN, which are heavy metals, were further added to the plating solution. At this time, the temperature of the plating liquid was adjusted to 70 ~ 90 ℃, the pH of the plating liquid was kept constant at 7.0 to 10.0 by sodium hydroxide. And about 30 g / l boric acid was used as a pH stabilizer. In this way, an electroless cobalt-tungsten-phosphoric tri-alloy plating solution was obtained.

<Manufacture example 1>

A plating solution was prepared by adding 20-40 g / l of sodium hypophosphite as a reducing agent to 10-20 g / l of cobalt acetate as a metal source, and 20-60 g / l of sodium citrate as a complexing agent. Then, 5-10 g / L ammonium tungstate was dissolved in sodium hydroxide solution and added to the plating solution in the form of ions. Further, as an additive, 10 to 1000 ppm of ammonium hypophosphite and 0.5 ppm of NaSCN were further added to the plating solution. At this time, the temperature of the plating liquid was adjusted to 60 ~ 90 ℃, the pH of the plating liquid was kept constant at 7.0 to 10.0 by sodium hydroxide. And about 30 g / l boric acid was used as a pH stabilizer. In this way, a neutral electroless cobalt-tungsten-phosphoric tri-alloy plating solution was obtained.

<Manufacture example 2>

A neutral electroless cobalt-tungsten-phosphor ternary alloy plating solution was obtained in the same manner as in Preparation Example 1, except that cobalt sulfate was used instead of cobalt acetate as a metal source.

Experimental Example: Performance Comparison of Three-Way Alloy Plating Solution According to the Present Invention

In order to compare the performance of the neutral three-way alloy plating solution according to the present invention, the following plating process was performed using the cobalt-tungsten-phosphorus three-way alloy plating solution prepared in Preparation Examples 1 and 2 and Comparative Preparation Example 1.

1) a pickling treatment of a wafer material having a thickness of 20 nm to titanium and copper of 100 nm to 150 nm for 1 to 2 minutes to remove an oxide film of copper at a temperature of 25 ° C. to 30 ° C .;

2) washing the wafer material with non-ionized water;

3) soft etching treatment and water washing treatment for 1-2 minutes in the temperature range of 20-30 ° C. to improve adhesion;

4) surface activation treatment with a palladium metal catalyst;

5) Plating process (In case of Comparative Preparation Example 1, the temperature of the plating liquid was kept constant at about 70 ° C., and the pH of the plating liquid was set at about 9.0. In the case of Production Examples 1 and 2, the temperature of the plating liquid was about 60 ° C.) Keep constant and set the pH of plating solution to about 8.5)

Between each process, two washing steps with pure water were removed to remove impurities on the surface in the previous step.

The appearance of crystal grains in each of the cobalt-tungsten-phosphorus tertiary alloy films obtained through this process was compared through FIGS. 1 to 3.

1 is a photograph of the appearance of the plating film formed by the plating solution prepared by Comparative Preparation Example 1, Figure 2 is a photograph of the appearance of the plating film formed by the plating solution prepared by Preparation Example 1 according to the present invention. And, Figure 3 is a photograph of the appearance of the plating film formed by the plating solution prepared by Preparation Example 2 according to the present invention.

Referring to FIG. 1, it can be seen that the crystal grains in the formed plating film are fine and no pits or cracks occur.

Referring to FIG. 2, it can be seen that the size of cobalt-tungsten-phosphate crystal grains vaccinated in the formed plating film is very similar to that of the plating film in FIG. 1, and no pits or cracks are generated.

In addition, referring to FIG. 3, as in the plating film shown in FIG. 2, it is confirmed that the crystal grains are very fine and no pits or cracks are generated.

In the case of the present invention, although the addition of ammonium hypophosphite was added instead of Pb, which is a heavy metal, the crystal grains became very fine and a large amount of pits formed in the plating film was added. It means that the crack is reduced. That is, in the case of using the neutral electroless cobalt-tungsten-phosphorus tri-alloy plating solution according to the present invention, not only 1) a plating film similar to that of Pb, which is a heavy metal, can be formed, but 2) the main cause of environmental pollution. By not using heavy metals such as Pb indicated as it can have the effect that it can prevent various environmental pollution that can occur due to the use of heavy metals. In addition, the plating is possible at a lower temperature of about 60 ℃, it can have the effect that the plating is possible at a lower pH.

On the other hand, the surface roughness of each cobalt- tungsten-phosphorus terpolymer coating obtained through this process is shown in Table 1. At this time, Ra means the center line mean roughness, RMS (Root Mean Square: the value calculated by dividing the square of the distance squared from the center line by the reference length and calculating the square root again) means the square mean roughness.

In addition, the surface of each of the cobalt- tungsten-phosphorus ternary alloy film obtained through the above process was analyzed by atomic force microscopy (AFM: Atomic Force Microscopy) and compared to this through FIGS. Figure 4 is a photograph of the atomic force microscope of the plating film formed by the plating solution prepared by Comparative Preparation Example 1, Figure 5 is an atomic force microscope of the plating film formed by the plating solution prepared by Preparation Example 1 according to the present invention It is a photograph, and FIG. 6 is a photograph of the atomic force microscope of the plating film formed by the plating liquid manufactured by the manufacture example 2 which concerns on this invention.

Comparative Production Example 1 (Fig. 4) Preparation Example 1 (FIG. 5) Preparation Example 2 (FIG. 6) Ra 2.34 nm 1.99 nm 2.89nm RMS 2.90nm 2.55nm 3.57nm

Referring to Table 1, when cobalt sulfate was used as a metal source and Pb and NaSCN, which are heavy metals, were added as additives (Comparative Preparation Example 1), Ra was 2.34 and RMS was 2.90. This result is a result of analyzing the photograph of the atomic force microscope shown in FIG.

When cobalt sulfate was used as a metal source and ammonium hypophosphite and NaSCN were added as additives instead of Pb (Preparation Example 2), Ra was 2.89 and RMS was 3.57, which results in the atoms shown in FIG. This is the result of analyzing the photo of force microscope.

When cobalt acetate was used as a metal source and ammonium hypophosphite and NaSCN were added as additives instead of Pb (Preparation Example 1), Ra was 1.99 and RMS was 2.55, which results in the atoms shown in FIG. 6. This is the result of analyzing the photo of force microscope.

In the case of Preparation Example 2, it can be seen that the roughness slightly increased when compared with Comparative Preparation Example 1, but in the case of Preparation Example 1, it was confirmed that the surface roughness is greatly reduced. .

This means that, in accordance with the present invention, the surface roughness of the cobalt-tungsten-phosphorus tri-alloy coating can be reduced and have a more dense surface structure, which means that the plating was carried out more effectively. It also shows that the cobalt-tungsten-phosphorus ternary alloy film is plated more smoothly, thereby preventing the diffusion of copper more effectively.

As mentioned above, although the present invention has been illustrated and described with reference to specific embodiments, the present invention is not limited thereto, and the following claims are not limited to the scope of the present invention without departing from the spirit and scope of the present invention. It can be easily understood by those skilled in the art that can be modified and modified.

Claims (10)

In the electroless cobalt-tungsten-phosphoric terpolymer plating solution,
Cobalt acetate or cobalt sulfate as ammonium salt, ammonium tungstate, sodium hypophosphite as reducing agent,
Characterized in that it further comprises an additive selected from the group consisting of ammonium hypophosphite, NaSCN, KSCN and mixtures thereof,
Electroless cobalt-tungsten-phosphoric terpolymer plating solution.
The method of claim 1,
The plating solution further comprises sodium citrate as a complexing agent and boric acid as a pH stabilizer.
Electroless cobalt-tungsten-phosphoric terpolymer plating solution.
The method of claim 2,
When the ammonium hypophosphite is added as the additive, the ammonium hypophosphite is added within a range of 10 to 1000 ppm, and
When the NaSCN is added as the additive, the NaSCN is characterized in that it is added within the range of 0.1 to 5.0ppm,
Electroless cobalt-tungsten-phosphoric terpolymer plating solution.
The method of claim 2,
The concentration of the cobalt acetate or the cobalt sulfate is 10 to 20 g / l, the concentration of the ammonium tungstate is 5 to 10 g / l, and the concentration of the sodium hypophosphite is 20 to 40 g / l Made,
Electroless cobalt-tungsten-phosphoric terpolymer plating solution.
The method of claim 4, wherein
Wherein the concentration of sodium citrate is 20 to 60 g / l, and the concentration of boric acid is about 30 g / l,
Electroless cobalt-tungsten-phosphoric terpolymer plating solution.
The method of claim 5,
PH of the plating liquid is controlled by sodium hydroxide, characterized in that 7.0 to 10.0,
Electroless cobalt-tungsten-phosphoric terpolymer plating solution.
The method of claim 5,
The ammonium tungstate is dissolved in sodium hydroxide solution and then added in the form of ions,
Electroless cobalt-tungsten-phosphoric terpolymer plating solution.
A method of forming a diffusion barrier layer on a metal surface by plating a metal using the electroless cobalt-tungsten-phosphorus tri-plating solution according to any one of claims 1 to 7,
Electroless Plating Process.
The method of claim 8,
The electroless plating process is characterized in that it is carried out in a temperature range of 60 to 90 ℃ and pH range of 7.0 to 10.0,
Electroless Plating Process.
It is plated on the metal surface by the electroless cobalt-tungsten-phosphorus tri-plating liquid solution as described in any one of Claims 1-7,
Cobalt-tungsten-phosphorus ternary alloy coating.

Images