KR20050052180A - Chemical mechanical polishing slurry containing a multi-functional additive - Google Patents

Abstract

The present invention provides a slurry for metal film CMP, which has improved dispersion stability by using a simple additive system, is easy to manage and store, and also has improved reproducibility of the slurry itself to ensure reproducibility of the CMP process. . Slurry for metal film CMP provided by the present invention, a multifunctional additive having a dispersion stability function, corrosion inhibitory function and oxidant stabilizer at the same time; Mechanical abrasives; And water. As the multifunctional additive, an amino alcohol compound can be used.

Description

Chemical mechanical polishing slurry containing a multi-functional additive

The present invention relates to a slurry for chemical mechanical polishing (CMP).

As semiconductor devices become finer and more dense, finer pattern formation techniques are being used. As a result, the surface structure of the semiconductor devices becomes more complicated and the steps between the interlayer films become larger.

In manufacturing semiconductor devices, the CMP process is used as a planarization technique for removing a step in a specific film formed on a substrate. In particular, a CMP process is widely used as a process for forming metal conductive films such as metal wirings, contact plugs, via contacts, and the like.

The CMP process is mechanically removed while chemically reacting the uneven surface of the wafer while moving the wafer and the polishing pad relatively while supplying the slurry to these contact portions while the surface of the wafer to be processed is in contact with the polishing pad. Wide area planarization technology to planarize.

In the CMP process, the polishing rate and the flatness of the polishing surface are very important, and these are determined by the process conditions of the CMP, the type of slurry, the type of polishing pad, and the like. Particularly important evaluation factors are scratches mainly caused by abrasive particles.

The pH of the slurry used in the CMP process for removing the metal film is generally in the range of 1 to 9, i.e., acidic and neutral regions. The biggest problem that arises from this is the agglomeration of abrasive particles due to destabilization of dispersion. This shortens the shelf life of the slurry and increases scratches.

The reason why agglomeration of the abrasive particles occurs is that, for example, when the abrasive particles are silica powder, the zeta potential of the silica particles shows a large negative value (eg, about -60 mV) in basicity, but the pH is This is because it gradually increases as it is lowered, and shows a value of almost zero at pH = 2. Accordingly, the electrostatic repulsive force between the silica particles is reduced to cause agglomeration of the particles, thereby increasing the secondary particle size of the silica powder. As a result, sedimentation of the silica secondary particles occurs.

Slurry for CMP is generally acidic and contains a chemical component capable of etching the metal in order to improve the polishing rate of the metal film. After the CMP process, the corrosive slurry remaining on the wafer surface corrodes the metal film, where in most cases the corrosion occurs non-uniformly across the surface of the polished metal film, resulting in very poor flatness of the wafer. In particular, excessive corrosion of the slurry in the via hole or contact process causes a key hole to be formed in the via or the contact, and the key hole lowers the electrical conductivity of the via or the contact. Therefore, it is necessary to suppress the metal film corrosion ability of the slurry for CMP, and also to make it possible to uniformly dissolve the metal by oxidation.

In the slurry for CMP, the most widely used oxidant component is hydrogen peroxide. Since hydrogen peroxide decomposes easily in the CMP process, the polishing rate of the CMP process can be reduced rapidly and unpredictably. In such a case, it is very difficult to ensure uniform reproducibility of the CMP process. Thus, stabilizing hydrogen peroxide in the slurry for CMP is very important.

Hydrogen peroxide is known to be rapidly decomposed by the transition metal present in the slurry. Thus, various additives have been used to minimize the reactivity of transition metals with hydrogen peroxide, such as, for example, chelate compounds or compounds containing p-orbital lone electrons.

As such, dispersion safety, corrosion inhibition and oxidant stability are important quality items for CMP slurries. In the conventional slurry for CMP, in order to secure corrosion inhibitory properties and oxidant stability, various additives having respective functions described above have been used in combination. However, the complex use of these various additives has the adverse effect of destroying the dispersion stability of the slurry at low pH.

The present invention provides a slurry for metal film CMP, which has improved dispersion stability by using a simple additive system, is easy to manage and store, and also has improved reproducibility of the slurry itself to ensure reproducibility of the CMP process. .

Slurry for metal film CMP provided by the present invention, a multifunctional additive having a dispersion stability function, corrosion inhibitory function and oxidant stabilizer at the same time; Mechanical abrasives; And water.

The multifunctional additive is a single compound having a dispersion stabilizing function, a corrosion inhibiting function and an oxidant stabilizing function simultaneously, or a mixture of similar compounds having a dispersion stabilizing function, a corrosion inhibiting function and an oxidant stabilizing function simultaneously.

Examples of such multifunctional additives include aminoalcohol compounds. The aminoalcohol compound refers to a compound having at least one amine group and at least one alcohol group. Such aminoalcohol compounds have a hydrophobic alkyl group and a hydrophilic functional group together.

The amine groups of aminoalcohol are adsorbed on the metal surface to suppress corrosion of the metal layer surface. In addition, the hydrophobic alkyl group and the hydrophilic functional group of the aminoalcohol improve the dispersibility of the mechanical abrasive particles. In addition, aminoalcohols have been shown to inhibit the decomposition reaction of hydrogen peroxide.

Specific examples of useful aminoalcohol compounds include 2-amino-2-methyl-2-propanol (2-amino-2-methyl-2-propanol (AMP)), triethanol amine (TEA), diethanol amine : DEA), monoethanol amine (MEA), 3-amino-1-propanol, 3-amino-1-propanol, 2-amino-1-propanol, 1- Amino-2-propanol, 1-amino-pentanol, and the like. However, the present invention is not necessarily limited thereto, and the compounds may be used alone or in combination. Particularly preferred aminoalcohol compounds are 2-amino-2-methyl-2-propanol, triethanol amine, or mixtures thereof.

The content of the multifunctional additive in the slurry for metal film CMP of the present invention is not particularly limited, but is preferably an appropriate amount capable of satisfying the dispersion stabilizer function of the mechanical abrasive, the corrosion inhibitory function of the oxidant, and the oxidant stabilizer simultaneously. .

If the content of the multifunctional additive is too small, the dispersion stability of the mechanical abrasive particles in the slurry may be lowered, the oxidant stabilizer and corrosion inhibitory function may not be sufficiently exhibited. If the content of the multifunctional additive is too large, excess amino alcohol may rather destroy the dispersion stability of the slurry, and excessively increase the adsorption of abrasive particles to the wafer surface induced by the amine groups of the amino alcohol.

In view of this point, the content of the multifunctional additive is preferably about 0.005 to about 5% by weight, more preferably about 0.05 to about 2% by weight, based on the total weight of the slurry for the metal film CMP of the present invention. %, Even more preferably about 0.05 to about 1% by weight.

The mechanical abrasive serves to polish the metal film through mechanical friction. Examples of the mechanical abrasive include silica powder such as fumed silica powder, colloidal silica powder, ceria powder, alumina powder and the like.

If the content of the mechanical abrasive in the metal film CMP slurry of the present invention is too small, the polishing rate of the CMP process may be excessively reduced, and if the content of the mechanical abrasive is too large, the aging stability of the slurry may be reduced.

In view of this, the content of the mechanical abrasive is preferably about 1 to about 20% by weight, more preferably about 1 to about 10% by weight, based on the total weight of the slurry for the metal film CMP of the present invention, Even more preferably about 2 to about 7% by weight.

As the average particle size of the mechanical abrasive is smaller, the dispersion stability of the slurry for the metal film CMP increases. If the average particle size of the mechanical abrasive is too small, the dispersion of the abrasive may be difficult due to the excessive specific surface area. If the average particle size of the mechanical abrasive is too large, it is difficult to maintain the dispersion stability of the slurry. In view of this, the average particle size of the mechanical abrasive may typically be about 5 to about 50 nm.

The water serves as a solvent for the dispersion medium of the mechanical abrasive powder and the multifunctional additive, preferably deionized water. The water content in the slurry for the metal film CMP is the remaining amount excluding the portion occupied by the mechanical abrasive and the multifunctional additive.

In the slurry for metal film CMP according to the present invention, the pH of the slurry can be adjusted to further improve its dispersion stability. When the pH of the slurry is too low, a handling risk may be large, and when the pH of the slurry is too high, it may adversely affect the dispersion stability of the slurry. Preferably, the pH of the slurry is about 2 to about 4.

In order to adjust the pH, the slurry for metal film CMP according to the present invention may further include a pH adjusting agent. As a pH adjuster, For example, inorganic acids, such as a sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc .; For example, organic acids containing carboxyl groups such as acetic acid, citric acid, glutaric acid, glycolic acid, formic acid, lactic acid, malic acid, maleic acid, oxalic acid, phthalic acid, succinic acid, tartaric acid and the like; Mixtures thereof and the like can be used. More preferably, nitric acid is used as the pH adjusting agent. The content of the pH adjuster in the slurry can be easily determined according to the desired pH value.

The slurry for metal film CMP according to the present invention may further include fluorine ions. One of the important factors to be considered in the CMP process for the metal film is the selectivity ratio between the metal film and the barrier film. For example, in the CMP process of the tungsten film, the smaller the difference in removal rate from the titanium constituting the barrier film, the smaller the amount of erosion of the surrounding oxide film. Fluorine ions serve to reduce the difference in removal rate between the metal film and the barrier film.

Fluorine ions are added to the slurry of the present invention in the form of a fluorine compound dissolved in water to dissociate fluorine ions. Examples of such fluorine compounds include, but are not limited to, ammonium fluoride, hydrofluoric acid, and the like. More preferred fluorine compound is ammonium fluoride. If the content of the fluorine compound is too small, the addition effect may be weak, and if the content is too large, the aggregation of the mechanical abrasive particles may be promoted. In view of this, the content of the fluorine compound may be preferably about 0.001 to about 1% by weight, more preferably about 0.001 to about 0.1% by weight based on the total weight of the slurry.

The slurry for the metal film CMP of the present invention can be mixed with an oxidizing agent and used in the CMP process of all metal films reactive with a mixture of hydrogen peroxide and transition metal salts, as well as tungsten, titanium, titanium nitride, copper, tantalum and tantalum nitride metal films. have.

As the oxidizing agent, a compound containing at least one peroxy group, a compound containing an element in the highest oxidation state, or a mixture thereof can be used. Specific examples of compounds containing one or more peroxy groups include, but are not limited to, hydrogen peroxide addition products such as hydrogen peroxide, urea hydrogen peroxide and percarbonates, organic peroxides such as benzoyl peroxide, peracetic acid and di-t-butyl peroxide, monopersulfate , Dipersulfate, sodium peroxide, mixtures thereof, and the like. Specific examples of the compound containing the element in the highest oxidation state include periodate, periodate, perbromic acid, perbromate, perchloroic acid, perchlorate, perboric acid, perborate, permanganate and the like. In addition, non-compounds may also be used if the electrochemical potentials are met. Specific examples of non-compounds that can be used include bromate, chromate, iodate, iodide, cerium (IV) compounds such as iodic acid and cerium ammonium nitrate, and the like. Most preferably hydrogen peroxide is used as the oxidizing agent.

An oxidant such as hydrogen peroxide is easily decomposed when mixed with the slurry in advance, and therefore mixed with the slurry of the present invention immediately before being used in the CMP process.

The slurry for the metal film CMP according to the present invention may further include an oxidizing aid. The oxidizing aid serves to further promote the oxidant to oxidize the metal film. Examples of useful oxidizing aids include nitrates, sulfates, perchlorates and halogenates of transition metals such as Ag, Co, Cu, Fe, Mo, Mn, Os, Ru, etc., sulfuric acid known as Mohr's salt. Hexahydrate ((NH ₄ ) ₂ Fe (SO ₄ ) ₂ .6H ₂ O) of ferric ammonium, and mixtures thereof. If the content of the oxidizing aid is too small, the addition effect may be weak, and if the content is too large, the decomposition rate of hydrogen peroxide may be excessively increased. In view of this, the content of the oxidizing aid may be preferably about 0.001 to about 2% by weight, more preferably about 0.01 to about 0.1% by weight based on the total weight of the slurry.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the technical idea of the present invention is not limited to the following examples.

<Example>

Preparation of Slurry for Metal Film CMP

Slurry samples for metal film CMP using various multifunctional additives according to the present invention were prepared (Examples 1 to 4). As the multifunctional additive, AMP, triethanolamine, 2-amino-1-propanol, and diethanolamine were used, respectively. As the mechanical abrasive, fumed silica having a surface area of 90 m ² / g was used. In addition to these, malonic acid was used as a pH regulator, and iron nitrate was used as an oxidizing aid.

The composition of the slurry of each Example was 5 g of multifunctional additives, 575 g of fumed silica, 3.4 g of malonic acid, 4.4 g of iron nitrate, and 9412 g of deionized water. The types of multifunctional additives used in each example are shown in Table 1. The slurry with this composition was evenly dispersed with a high pressure disperser from "Microfluidics".

For comparison, a slurry for CMP using no additives having a dispersion stability function, a corrosion inhibiting function, or an oxidant stability function was prepared (Comparative Example 1). The composition of Comparative Example 1 was 575 g of fumed silica, 3.4 g of malonic acid, 4.4 g of iron nitrate, and 9417 g of deionized water.

Evaluation of dispersion stability

While leaving each slurry, changes in the size of secondary particles and formation of precipitates were observed over time. The size of the secondary particles was measured 1 day and 15 days after slurry production using LA-910 manufactured by Horiba. The measurement results are shown in Table 1.

sample Multifunctional additive Secondary particle size (nm) 1 day later 15 days later Example 1 AMP 139 166 Example 2 Triethanolamine 142 170 Example 3 2-amino-1-propanol 146 174 Example 4 Diethanolamine 145 213 Comparative Example 1 none 153 246

As shown in Table 1, the secondary particle size of the silica powder in the slurry of Examples 1 to 4 measured one day after the preparation was not only smaller than that of the slurry of Comparative Example 1, but also measured after 15 days after the preparation. The secondary particle size of the silica powder in the slurry of ˜4 is also smaller than the slurry of Comparative Example 1. This shows that the dispersion stability of the slurry of the present invention using the multifunctional additive is very excellent.

Therefore, the slurry of the present invention can minimize the agglomeration of the mechanical abrasive particles, can prevent the occurrence of scratches in the CMP process, and can exhibit excellent polishing reproducibility.

Evaluation of Corrosion Inhibition Function

Tungsten wafers were immersed in each slurry for 30 minutes, then recovered and dried. Then the resistance of each tungsten wafer was measured to determine its thickness. From this thickness change, the etch rate for each tungsten wafer was calculated in dl / min. Table 2 shows the etching rates of tungsten wafers with each slurry.

sample Multifunctional additive Etching Speed (Å / min) Example 1 AMP 54.0 Example 2 Triethanolamine 57.3 Example 3 2-amino-1-propanol 63.3 Example 4 Diethanolamine 62.1 Comparative Example 1 none 65.8

As shown in Table 2, the etching rate by the slurry of Examples 1-4 is smaller than the etching rate by the slurry of Comparative Example 1. This shows that the corrosion inhibitive function of the slurry of the present invention using the multifunctional additive is very excellent.

In the case of semiconductor wafer processing, the etching rate of the tungsten film is a factor causing dishing of the patterned wafer. The slurry of the present invention can greatly increase the yield of semiconductor devices by minimizing this.

Evaluation of oxidant stabilization function

Hydrogen peroxide concentration change measurement and tungsten polishing experiments were carried out using the slurry of Comparative Example 1 mixed with hydrogen peroxide and the slurry of Example 1 mixed with hydrogen peroxide. At this time, CMP process conditions were 200 g / cm <^{2> of} down force, 50 rpm of table speeds, 40 rpm of carrier speeds, and 200 ml / min of slurry flow rates. The results are summarized in Table 3.

sample Immediately after mixing hydrogen peroxide 6 days after mixing hydrogen peroxide Polishing Speed Variation Hydrogen peroxide content (% by weight) Tungsten Polishing Speed (Å / min) Hydrogen peroxide content (% by weight) Tungsten Polishing Speed (Å / min) Example 1 99.5 1253 64.3 923 26% Comparative Example 1 99.5 1492 58.9 1032 31%

As shown in Table 3, 6 days after the hydrogen peroxide mixture, the hydrogen peroxide content of Example 1 is higher than the hydrogen peroxide content of Comparative Example 1. From this, it can be seen that the hydrogen peroxide stabilization function of the slurry of the present invention containing the multifunctional additive is very excellent. In addition, the polishing rate change rate of Example 1 is lower than the polishing rate change rate of Comparative Example 1, which means that the polishing reproducibility of the slurry of the present invention is excellent.

SEM photo observation of etched tungsten wafer surface

1 is an SEM photograph of the surface of the tungsten wafer after etching with the slurry of Example 1; From FIG. 1, it can be seen that contamination by the mechanical abrasive particles remaining on the surface of the tungsten wafer is very small, and the occurrence of scratches is suppressed.

By using the multifunctional additive, the slurry for CMP of the present invention to which the simple additive system is applied not only has excellent corrosion inhibiting function and oxidant stabilizing function, but also has improved dispersion stability. The slurry for CMP of the present invention is easy to manage and store, exhibits sufficient polishing speed in the CMP process, minimizes corrosion, erosion, scratches, contamination, etc. of the surface to be polished, as well as reproducible quality of the slurry itself. This is high. Therefore, the reproducibility of a CMP process can be improved by using the slurry for CMP of this invention.

1 is a SEM photograph of the surface of a tungsten wafer etched with a slurry according to the present invention.

Claims (11)

Multifunctional additives having a dispersion stability function, a corrosion inhibitory function, and an oxidant stabilizer function simultaneously; Mechanical abrasives; And Slurry for metal film CMP containing water. The slurry of claim 1, wherein the multifunctional additive is an aminoalcohol compound or a mixture of aminoalcohol compounds. 3. The amino alcohol compound according to claim 2, wherein the amino alcohol compound is 2-amino-2-methyl-2-propanol, triethanol amine, diethanol amine, monoethanol amine, 3-amino-1-propanol, 2-amino-1-propanol At least one selected from 1-amino-2-propanol and 1-amino-pentanol. The slurry of claim 1, wherein the content of the multifunctional additive is 0.005 to 5 wt%. The slurry of claim 1, wherein the mechanical abrasive is contained in an amount of 1 to 20% by weight. The slurry of claim 1, wherein the mechanical abrasive is silica powder, ceria powder, alumina powder, or a mixture thereof. The slurry of claim 1, wherein the average particle size of the mechanical abrasive is 5 to 50 nm. The slurry of claim 1 wherein the pH value is 2-8. The slurry of claim 1, further comprising an inorganic acid or an organic acid as a pH adjusting agent. The slurry of claim 1, further comprising fluorine ions. The slurry of claim 1, further comprising an oxidizing aid.