KR100600598B1 - Slurry Composition for Chemical Mechanical Polishing of Tungsten Wire - Google Patents

Abstract

The present invention relates to a metal CMP (Metal Chemical Mechanical Polishing) slurry composition excellent in polishing performance and polishing reproducibility, but does not cause polishing defects, and more particularly, an inorganic acid and a peroxide compound, an organic acid compound having at least one carboxyl group as an oxidizing agent, A slurry composition for metal CMP containing a metal oxide and deionized water as an abrasive. The composition according to the present invention not only has excellent chemical polishing ability, but also significantly reduces polishing defects such as oxide erosion, corrosion, pits, dishing, scratches, and the like, which are generated when applied to the CMP process, and the storage stability and abrasive reproducibility of the slurry. Significantly improved.

Description

Slurry Composition for Chemical Mechanical Polishing of Tungsten Wire

FIG. 1 is a diagram schematically showing a cross section of a device in which oxide erosion has occurred by a metal CMP process, and FIG. 2 is a diagram schematically showing a cross section of a device in which corrosion occurs by a metal CMP process.

The present invention relates to a metal CMP (Metal Chemical Mechanical Polishing) slurry composition having excellent polishing power and polishing reproducibility but not causing defects. More specifically, the present invention relates to an inorganic acid and a peroxide compound as an oxidizing agent, an organic acid compound having at least one carboxyl group, and an abrasive. It relates to a slurry composition for metal CMP containing a metal oxide and deionized water.

In the multi-layer polishing process or double damascene process of the integrated circuit developed to increase the integration degree of the IC circuit, the CMP process is mainly used to planarize the wafer surface. The CMP process is a polishing method in which the surface of a wafer is planarized using a polishing pad and a slurry during semiconductor manufacturing. The polishing pad and the wafer are brought into contact with each other, and the wafers are mechanically and chemically processed by performing an orbital movement in which rotation and linear motions are mixed. In the polishing process, the slurry generally contains an abrasive which is physically abrasive and an active ingredient which is chemically polished, for example, an etchant or an oxidizing agent, Thereby selectively etching the protruding portions on the wafer surface to provide a flat surface.

CMP slurries can be divided into oxide CMP slurries for polishing the SiO ₂ layer, which is an insulating layer, and metal CMP slurries for polishing tungsten or aluminum, depending on the polishing object. Among these, metal CMP slurries are especially tungsten interconnects and tungsten Attention has been drawn to the preferred method for polishing tungsten in the formation of contacts / via plugs. In the case of tungsten junctions mainly formed by CVD (Chemical Vapor Deposition), the wafer should be flattened by removing tungsten remaining on the surface of the insulating layer for the next process after deposition. In this case, only tungsten can be selectively polished without affecting the insulating material, and so-called over etching, in which the tung inside the via is removed, in particular compared to reactive ion etching (RIE). ) Can be avoided and the risk of defects caused by particles remaining on the wafer after ion etching can be eliminated.

However, in general, the metal CMP slurry containing abrasives, oxidants, and deionized water is used to increase the oxidizing power of the oxidizing agent or to use an excessive amount of oxidizing agent in order to obtain a high polishing rate. It is additionally used. For example, U.S. Pat.Nos. 5,980,775 and 5,958,288 disclose slurries that significantly increase the oxidative power by additionally containing metal catalysts while using peroxide compounds as oxidants, and U.S. Pat.Nos. 5,340,370 and 5,527,423 are single. A slurry in which an excess of an oxidant is added to obtain a high polishing rate while using an oxidant is disclosed. However, as in the prior art, a metal polishing slurry in which the oxidation power of the slurry is increased in order to obtain a high polishing rate is obtained by the oxide erosion of the insulating layer (see FIG. 1) and corrosion resulting in a reduction of the metal layer. corrosion (refer to FIG. 2), pit, dishing, scratching, and other defects, and the like, and in the presence of an excessive amount of oxidant, there is a problem in that the dispersion stability and abrasive reproducibility of the slurry are greatly deteriorated.

In addition, even in the case of a slurry using an oxidizing agent having a high oxidizing power in the polishing mechanism, although the initial polishing rate has a high polishing rate, the concentration of the metal oxide polished in the slurry increases as polishing progresses, so that the surface of the polished metal oxide is polished. Re-adsorption occurs in the polishing does not proceed further polishing has a problem of poor polishing reproducibility.

Therefore, in the CMP process field, it is possible to provide a high polishing rate without using excessive oxidizing agent or an oxidizing agent having an excessively high oxidizing power, and to provide a slurry composition for metal CMP having excellent slurry dispersion stability and polishing reproducibility. There has been a demand.

The present inventors earnestly studied to solve the above problems, and as a result, in the case of a slurry composition containing an inorganic acid and a peroxide compound as the oxidizing agent, and an organic acid compound containing at least one carboxyl group such as glycolic acid, without using an excess oxidizing agent, In addition to providing a high polishing rate, defects during polishing were significantly reduced, dispersion stability and storage stability of the obtained slurry composition were greatly improved, and polishing reproducibility was also excellent, and the present invention was completed.

After all, the present invention is to provide a metal CMP slurry excellent in polishing performance, storage stability and polishing reproducibility, and can greatly reduce defects during polishing.

One aspect of the present invention for achieving the above object relates to a slurry composition for metal CMP comprising an inorganic acid and a peroxide compound, an organic acid compound having at least one carboxyl group as an oxidizing agent, an abrasive and deionized water.

Another aspect of the invention relates to a method of polishing a metal using the composition.

Hereinafter, the present invention will be described in more detail.

The slurry according to the present invention can provide a high polishing rate by using a combination of a peroxide compound and an inorganic acid together as an oxidizing agent. In this case, the peroxide compound has a high redox potential value, but the oxidation rate is low so that the polishing rate is not excessive. On the other hand, the inorganic acid has a role as an oxidizing agent and a pH adjusting agent, while no defects occur.

Examples of the peroxide compound that can be used include hydrogen peroxide, benzoyl peroxide, calcium peroxide, barium peroxide, or sodium peroxide, or mixtures thereof. Preferably, hydrogen peroxide is used in terms of oxidizing power and slurry dispersion stability. The peroxide compound is used in an amount of 0.1 to 10 wt%, preferably 0.5 to 5 wt%, based on the total weight of the composition.

As an example of the inorganic acid that can be used in the slurry of the present invention, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or a mixture thereof can be used. Given the problem of contamination after polishing, nitric acid is most preferred. The amount of the inorganic acid is used in 0.001 to 0.1% by weight, preferably 0.001 to 0.05% by weight based on the total weight of the composition.

When the amount of the peroxide compound and the inorganic acid used exceeds the above range, there is a high possibility that defects such as oxide erosion or metal layer corrosion occur, and when it falls below the above range, a sufficient polishing rate cannot be obtained.

In general, when the oxidizing agent of the composition described above is used, the polishing rate is not applicable to a normal semiconductor process, whereas when an excessive amount of peroxide compound is used to increase the polishing rate, oxide erosion, metal layer overcorrosion, etc. The higher the possibility of defects, the excessive use of the inorganic acid, the acidity of the slurry is too high, there was a problem that the handling difficulty increases. However, according to the present invention, acetic acid, citric acid, glutaric acid, glycolic acid, glycolic acid, formic acid, lactic acid, malic acid ), Maleic acid, oxalic acid, phthalic acid, succinic acid, or tartaric acid such as by adding an organic acid compound having at least one carboxyl group. The problem can be solved. It is more preferable to add glycolic acid. In addition, according to the research of the present inventors, carboxylic acid such as glycolic acid forms a complex with a metal oxide such as W _x O _y desorbed from the tungsten surface by mechanical action to oxidatively stably remove the desorbed polishing oxide from the reaction system. In addition to improving the adhesion of the polished metal oxides to the re-adsorption of the polishing oxide effectively, it is possible to provide excellent abrasive reproducibility, and the selectivity of tungsten and oxide that occurs during metal polishing Can be increased. On the other hand, when a carboxylic acid such as glycolic acid is added to the slurry, the storage stability of the slurry is greatly improved, and even when the slurry is used after long-term storage, polishing reproducibility such as scratching and polishing rate is kept constant. In CMP slurry, when silica is used as the abrasive, the absolute value of the isoelectric point is smallest in the range of pH 2 to 4, so that the reaggregation of the abrasive occurs spontaneously over time. In case of long-term storage of slurry, large particles of reaggregated abrasives are produced, and scratch and sedimentation are serious. However, in the case of the composition according to the present invention, the long-term storage stability of the slurry is improved by the glycolic acid and the like also perform a buffer and a hinder to prevent reaggregation between the abrasive particles. Carboxylic acid addition amount, such as glycolic acid, is 0.01-10 wt%, Preferably it is the range of 0.1-2 wt%. In the case of excessive addition of carboxylic acid, the dispersion stability of the slurry may be lowered, and when added in a smaller amount than the above range, the object to be obtained in the present invention cannot be obtained.

The slurry composition according to the present invention contains a metal oxide as an abrasive for physical polishing. The metal oxide is usually in the form of fine powder, and may be used as the fine powder of all known metal oxides usable in the composition for CMP. Examples of metal oxides that can be used include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titania and ceria. When using silica, it is advantageous at the point which is excellent in dispersion stability and few scratches. The metal oxide may be used alone or as a mixture of two or more oxides. The content of the metal oxide is preferably 0.1 to 10% by weight, preferably 1 to 7% by weight, based on the weight of the entire slurry composition. . If the content of the fine metal oxide powder exceeds 10% by weight, it is difficult to control the dispersion stability and polishing rate. If the content is less than 0.1% by weight, the dispersibility is good but the amount of the abrasive particles is small, so the physical polishing performance is expected. Difficult to do

The slurry composition according to the present invention can be usefully used for the CMP process for metal polishing in the semiconductor process, preferably for polishing tungsten, aluminum or copper metal.

Hereinafter, the structure and effect of the present invention will be described in more detail with specific examples and comparative examples, but these examples are only intended to more clearly understand the present invention, and are not intended to limit the scope of the present invention.

EXAMPLE

Examples 1 to 3

To a mixture of 50 g of commercially available Aerosil 90G (manufactured by Degussa), 915.7 g of deionized water, 0.3 g of nitric acid, and 20.0 g of hydrogen peroxide, glycolic acid was added in an amount as shown in Table 1 below, and then, in a 2 l flask (material: polyethylene) Stirred for a time (rate: 2,000 rpm). The mixture was dispersed at 1,200 psi by high pressure dispersion to obtain a slurry, which was filtered through a filter having a depth of 1 μm to prepare a slurry composition for CMP. After polishing for 2 minutes under the following conditions, the results are shown in Table 1:

   o Grinder Model: 6EC (STRASBAUGH)

   o Polishing condition:

    Pad type: IC1400 / SubaIV Stacked (Rodel)

    Platen Speed: 75 rpm

    Quill Speed: 35 rpm

    Pressure: 4 psi

    Back Pressure: 0 psi

    -Temperature: 25 ℃

    Slurry flow: 250 ml / min

   o Polishing target:

A W blanket wafer fabricated by depositing 1000 Å of HTO on a poly-Si substrate and depositing 1000 Å and 10,000 Å of TiN and W, respectively.

On the other hand, for Example 2, the corrosion rate and the oxide erosion was measured and the results are shown in Table 2, and the elapsed days after leaving the slurry according to Example 2 at room temperature (0 days, 30 days, 60 days, 120 days) The difference in polishing rate and average particle size according to the one) are shown in Table 3. In this case, the corrosion rate was measured by etching rate after wet etching by dipping the W wafer in the slurry for 60 minutes, and the average particle size was measured by ELS 8000 of Ostuka.

Comparative Example 1

A slurry was prepared in the same manner as in Example 1 except that glycolic acid was not added, and a polishing process was performed. The results of the measurement of the polishing rate are shown in Table 1, and after leaving the slurry at room temperature, the difference in polishing rate and average particle size were measured according to the elapsed days (0, 30, 60, 120 days). Shown in

Comparative Example 2

Polishing was performed in the same manner as in Example 1, except that 15 g of Fe (NO ₃ ) ₃ was used instead of glycolic acid, and the corrosion rate and oxide erosion were measured. The results are shown in Table 2.

Comparative Example 3

Polishing was performed in the same manner as in Example 1, except that 20 g of KIO ₃ was used instead of glycolic acid, and the corrosion rate and oxide erosion were measured. The results are shown in Table 2.

sample Glycolic acid added amount W grinding speed P-TEOS Polishing Speed Example 1 0.1g 1,112 Å / min 55 Å / min Example 2 5.0 g 2,486 Å / min 85 Å / min Example 3 15.0 g 2,714 t / min 115 Å / min Comparative Example 1 - 825 Å / min 43Å / min

Where P-TEOS is poly-tetraethylorthosilicate

sample Glycolic acid Fe (NO ₃ ) ₃ KIO ₃ W grinding speed Corrosion rate Oxide erosion Example 2 5.0 g - - 2486 Å / min 10 Å / min 85 Å Comparative Example 2 - 15.0 g - 2445 Å / min 120Å / min 460 yen Comparative Example 3 - - 20.0 g 2718Å / min 150 Å / min 328 yen

sample Polishing speed after 0 days Polishing speed after 30 days Polishing speed after 60 days Polishing speed after 120 days Example 2 2486 Å / min 2444 Å / min 2425 Å / min 2410Å / min Comparative Example 1 852 Å / min 413Å / min 376Å / min 361Å / min

From Tables 1 to 3, it can be seen that the addition of glycolic acid significantly reduces the corrosion rate and oxide erosion and greatly improves the storage stability while maintaining the polishing rate of the slurry.

In the case of the CMP composition according to the present invention, by adding carboxylic acid such as glycolic acid to the peroxide compound and the organic oxidant used as the oxidizing agent, oxide erosion, metal layer corrosion, pitch, dishing, etc. generated in the CMP process even under a high polishing rate It is possible to prevent the problem, and to prevent the decomposition of the oxidizing agent such as peroxide compound to maintain the oxidizing power of the slurry can improve the polishing reproducibility and storage stability of the slurry.

Claims (3)

A slurry composition comprising a metal oxide as an abrasive, a peroxide compound as an oxidant, an inorganic acid, and deionized water, wherein the slurry composition further comprises glycolic acid as an oxidizing agent. The method of claim 1, wherein the metal oxide is silica, aluminum, ceria, titania or mixtures thereof, and the peroxide compound is hydrogen peroxide, benzoyl peroxide, calcium peroxide, barium peroxide ( barium peroxide, or sodium peroxide, or mixtures thereof, wherein the inorganic acid is nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, or a mixture thereof. Tungsten wiring polishing CMP slurry composition, characterized in that. According to claim 1 or 2, wherein the metal oxide is 0.1 to 10% by weight, the peroxide compound is 0.1 to 10% by weight, the inorganic acid is 0.001 to 0.1% by weight based on the total weight of the composition, The glycolic acid is tungsten wire polishing CMP slurry composition comprising 0.01 to 10% by weight.

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