KR100442549B1 - Slurry Composition for Chemical Mechanical Polishing of Metal having Enhanced Polishing Ability and Improved Stability and a Method for Preparing the Slurry Composition - Google Patents

Abstract

The present invention relates to a slurry composition for CMP (Chemical Mechanical Polishing) for metal polishing, and to a method for producing the same, more specifically, metal oxides, hydrogen peroxide, iron compounds, imidazole compounds, And a deionized water and having a pH of 2 to 4, the slurry composition for CMP for metal polishing, which is excellent in polishing performance and excellent in chemical and dispersion stability, and a method for producing the slurry composition.

According to the present invention, it is possible to prepare a composition for CMP for metal polishing, which is capable of maintaining excellent polishing performance while using a relatively small amount of oxidizing agent, as well as significantly improving chemical and dispersion stability, and having excellent storage stability of the composition. .

Description

Slurry Composition for Chemical Mechanical Polishing of Metal having Enhanced Polishing Ability and Improved Stability and a Method for Preparing the Slurry Composition}

The present invention relates to a slurry composition for CMP (Chemical Mechanical Polishing) for metal polishing, and to a method for producing the same, more specifically, metal oxides, hydrogen peroxide, iron compounds, imidazole compounds, And a deionized water and having a pH of 2 to 4, the slurry composition for CMP for metal polishing, which is excellent in polishing performance and excellent in chemical and dispersion stability, and a method for producing the slurry composition.

As the integration of IC circuits increases, the process requirements required in the manufacturing process increase, and in particular, the requirements for flatness of semiconductor wafers become strict. Flatness affects the optical focusing characteristics of optical stepper devices, and its importance is increasing as the depth of the optical lens decreases for improved resolution, and high flatness even when forming metal interconnects on the wafer. Tao is required. Various methods are used in the planarization process, but CMP process is mainly used in a difficult process, for example, multi-layer polishing or dual demascene of an integrated circuit. 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 production. The polishing process refers to a process in which the slurry polishes the wafer while contacting the polishing pad and the wafer with rotation and linear movement. At this time, the slurry generally contains an abrasive which is physically abrasive and an active component which is chemically polished, such as an etchant or an oxidant, so that the exposed part of the wafer surface is physicochemically. Selective etching provides a flat surface.

The CMP process is of particular interest as a preferred method for polishing tungsten in the formation of tungsten interconnects and tungsten contacts / via plugs. Tungsten junctions and the like are mainly formed by chemical vapor deposition (CVD), where the wafer is planarized by removing the tungsten remaining on the surface of the insulating layer for the next step after deposition. Using the CMP process to remove tungsten, it is advantageous to selectively polish tungsten without affecting the insulating material, especially over etching compared to reactive ion etching (RIE). There is an advantage to avoid.

In the case of the CMP slurry for metal polishing, the slurry generally contains an abrasive, an oxidizing agent, a pH adjuster, and deionized water. As an example of a known composition for CMP, US Pat. No. 5,244,534 discloses a composition comprising an alumina abrasive, hydrogen peroxide (oxidant) and ammonium hydroxide or potassium hydroxide (pH regulator). However, in the case of the patent, first of all, polishing is not good in that it must proceed in two steps, and since hydrogen peroxide is used as the sole oxidant, an excess of hydrogen peroxide is used to maintain a predetermined polishing rate during polishing. That is, generally, excessive hydrogen peroxide should be used because chemically unstable hydrogen peroxide is continuously decomposed in an aqueous solution and the polishing performance of the polishing slurry is severely degraded over time. The use of such excess oxidant not only increases the incidence of defects such as scratches, but also has a limit of storage stability even when used in excess, and seriously deteriorates dispersibility due to decomposition of hydrogen peroxide.

As another example of a slurry composition for CMP, US Pat. No. 5,340,370 discloses a composition comprising silica (polishing agent), potassium ferricyanide (oxidizing agent), and adjusting the pH to 2-4. The patent eliminates the use of hydrogen peroxide and solves the problem of overuse and storage stability due to decomposition of hydrogen peroxide by using iron oxide compounds as oxidants, but according to the experiments of the present inventors the composition is hydrogen peroxide in terms of polishing rate Since it is not better than using an excessive amount of iron compounds to maintain a predetermined polishing rate, there is a problem that can not prevent metal contamination on the wafer. Since the metal contamination due to the slurry causes short circuit or disconnection between the metal wiring film and the insulating film of the semiconductor chip, it is very important to prevent metal contamination.

Therefore, in the CMP process, it is possible to maintain a constant polishing rate while using a relatively small amount of oxidizing agent, excellent dispersion stability and chemical stability, and excellent storage stability so that it can be used without remixing the slurry even after a certain period of storage. Eggplants have been in demand for slurry compositions.

The present inventors earnestly studied to develop a slurry for CMP for metal polishing, which has sufficient chemical activity even when using a relatively small amount of oxidizing agent, maintains a high polishing rate, and has excellent chemical and dispersion stability. The present invention was completed by confirming that an excellent composition for CMP that satisfies the above conditions can be obtained by using an iron compound and hydrogen peroxide together as an oxidant and further using an imidazole compound.

After all, the present invention is to provide a slurry for CMP and a method for producing the same for polishing the metal having excellent polishing performance, chemical stability and dispersion stability, and excellent storage stability.

The present invention relates to a slurry composition for CMP for metal polishing, and to a method for producing the same, which has excellent polishing performance and improved stability, and more particularly, includes metal oxides, hydrogen peroxide, iron compounds, imidazole compounds, and deionized water. And a pH of 2 to 4, and a slurry composition for CMP for metal polishing, and a method for producing the same.

Hereinafter, the components and the preparation method of the slurry composition according to the present invention will be described in detail.

The slurry composition according to the present invention contains a metal oxide for physical polishing, which is usually in the form of fine powder. Metal oxides usable in the present invention include fine powders of all known metal oxides that can be used in the composition for CMP, and include, for example, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titania and ceria. ), And the like. The metal oxides may be used alone or as a mixture of two or more oxides. The content of the metal oxide is preferably 0.1 to 25% by weight based on the weight of the total slurry composition. More preferably, it is 2 to 13% by weight for silica and 0.5 to 10% by weight for alumina, titania, ceria and the like. If the content of the fine metal oxide powder exceeds 25% by weight, it is difficult to control the dispersion stability and polishing rate. If the content of the metal oxide fine powder is less than 0.1% by weight, the dispersibility is good but the amount of the abrasive particles is small, so that the physical polishing performance is expected. it's difficult. In addition, the specific surface area of the fine metal oxide powder is sufficient to have a conventional specific surface area used in the CMP composition, but preferably has a range from 50 m 2 / g to 200 m 2 / g. If the specific surface area of the metal oxide is less than the above range, it is difficult to apply to the actual process due to the small difference according to the film quality of the smoke screen, if the above range, the dispersion stability is significantly lowered may be difficult to long-term storage of the slurry.

The slurry composition according to the present invention contains a complex oxidizing agent consisting of hydrogen peroxide and an iron compound as an active compound (ie, an oxidizing agent) for chemical polishing. According to the research of the present inventors, the secondary oxidant of the complex oxidant, not only serves as an oxidant, but also weakens the hardness of the oxide film formed on the surface of the wafer due to the oxidation of hydrogen peroxide, which is a primary oxidant, to facilitate the oxide film. It serves to remove, thereby significantly reducing the amount of hydrogen peroxide used. In addition, due to the excellent oxidizing performance of hydrogen peroxide can be obtained while maintaining a good polishing rate while maintaining the use amount of the iron compound, the secondary oxidizing agent at a lower level, it is possible to further prevent metal contamination due to the use of the iron compound. Examples of the iron compound that serves as a secondary oxidant in the composition according to the present invention include iron nitrate, iron phosphate, and ferric cynide, preferably iron nitrate. use. The iron compound may be used alone or as a mixture of two or more compounds. The hydrogen peroxide content used as the primary oxidant is 1 to 3% by weight, preferably 1.5 to 2.5% by weight, based on the total weight of the composition. The content of the iron compound used as the secondary oxidizing agent is preferably from 0.03 to 0.1% by weight, more preferably from 0.05 to 0.07% by weight based on the total weight of the slurry. When the content of the hydrogen peroxide and the iron compound exceeds the above range, erosion or dishing occurs badly in the plug of the semiconductor circuit, which is not preferable. In particular, when the iron compound is added in excess, the dispersion stability of the slurry is lowered, and when polishing, corrosion or pitching occurs, thereby lowering the yield of semiconductor circuits. On the other hand, in the case of containing hydrogen peroxide and iron compounds in the above range, the chemical activity of the slurry is weak, it is difficult to achieve effective polishing.

The slurry for CMP according to the present invention further contains an imidazole compound, and examples of the imidazole compound include 4-imidazolmethanol, 4-imidazole ethanol and 4-imidazole carboxylic acid. The imidazole compound may be used alone or in a mixture of two or more compounds. According to the researches of the present inventors, the imidazole compound not only prevents the continuous decomposition of hydrogen peroxide, but also serves to suppress the reaction of the iron compound and hydrogen peroxide used in the present invention to provide a slurry having excellent dispersion stability and chemical stability. The content of the imidazole compound is 0.001 to 0.5% by weight, more preferably 0.005 to 0.1% by weight based on the total weight of the slurry. When the amount of the imidazole compound is less than 0.001% by weight, the present invention is unable to achieve the desired dispersion stability and chemical stability, and when the amount is more than 0.5% by weight, the expected polishing ability cannot properly exhibit the oxidizing power of hydrogen peroxide used as the oxidant. Can't get speed

The slurry for CMP according to the present invention maintains the overall pH at 2-4. For this purpose, a known acid compound used for pH control in the composition for CMP is used, and examples of the acid compound include nitric acid or acetic acid. Preferably nitric acid is used.

In the slurry composition for CMP according to the present invention, first, a fine metal oxide powder is added to an aqueous solution in which an iron compound and an acid compound are dissolved in deionized water, and the mixture obtained by stirring the mixture at a temperature of 5 ° C. to 30 ° C. for a predetermined time (for example, For example, the resulting slurry is dispersed by a high pressure dispersion method or the like, and the obtained slurry is filtered to remove impurities, and then, hydrogen peroxide and an imidazole compound are mixed with the slurry.

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

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

Example 1

An aqueous solution was prepared by adding 0.3 g of iron nitrate and 0.4 g of nitric acid to 935.5 g of deionized water, and 53 g of commercially available Aerosil 90G (manufactured by Degussa) was mixed in the aqueous solution for 2 hours in a 2 liter flask (material: polyethylene). Stirring (rate: 2,000 rpm) gave a mixture. The mixture was dispersed once under high pressure dispersion at 1,200 psi to obtain a slurry, which was filtered through a filter having a depth of 1 μm, and then 10 g of hydrogen peroxide (50%) and 0.8 g of 4-imidazolmethanol were added to the obtained slurry. And mixed, to prepare a slurry composition for CMP. After polishing for 2 minutes under the following conditions, the polishing rate was measured three times from the thickness change removed by polishing:

o Grinder Model: 6EC (STRASBAUGH)

o Polishing condition:

Pad type: IC1000 / SubaIV Stacked (Rodel)

Platen Speed: 120 rpm

Quill Speed: 120 rpm

Pressure: 6 psi

Back Pressure: 0 psi

-Temperature: 25 ℃

Slurry flow: 150 ml / min

o Polishing target:

Wafer 1: 6-inch wafer with tungsten

Wafer 2: 6-inch wafer with copper

The polishing performance was evaluated by the wafer non-uniformity (WIWNU) measured by comparing the polishing rate and the difference in wafer thickness before and after polishing. The results are shown in Table 1. As shown in Table 1, the slurry composition of Example 1 exhibited high polishing rates of more than 3200 Å / min when tungsten wire polishing and 3800 Å / min when copper wire polishing, 1.1% (tungsten wire polishing) and 1.5% ( Copper wiring polishing).

Example 2

A slurry was prepared in the same manner as in Example 1 except that the amount of 4-imidazolmethanol added was 2.2 g, polishing was performed, and polishing performance was evaluated. The evaluation results are shown in Table 1. As shown in Table 1, the slurry composition of Example 2 exhibited a high polishing rate of 3000 m 3 / min at tungsten wire polishing and 3500 m 3 / min at copper wire polishing, and 1.0% (tungsten wire polishing) and 1.4% ( Copper wiring polishing).

Example 3

A slurry was prepared in the same manner as in Example 1, except that 0.8 g of 4-imidazole carboxylic acid was added instead of 4-imidazol methanol, and polishing performance was evaluated. The evaluation results are shown in Table 1. As shown in Table 1, the slurry composition of Example 2 exhibited high polishing rates of more than 3180 Å / min when tungsten wire polishing and 3690 Å / min when copper wire polishing, and 1.3% (tungsten wire polishing) and 1.3% ( Copper wiring polishing).

Example 4

A slurry was prepared in the same manner as in Example 1 except that 2.2 g of 4-imidazole carboxylic acid was added instead of 4-imidazol methanol, and polishing performance was evaluated. The evaluation results are shown in Table 1. As shown in Table 1, the slurry composition of Example 4 exhibited a high polishing rate of more than 3000 m 3 / min at tungsten wire polishing and 3500 m 3 / min at copper wiring polishing, and 1.2% (tungsten wire polishing) and 1.1% ( Copper wiring polishing).

Example 5

As a metal oxide fine powder, except that alumina was used instead of silica, a slurry was prepared in the same manner as in Example 1, and polishing was performed, and polishing performance was evaluated. The evaluation results are shown in Table 1. As shown in Table 1, the slurry composition of Example 5 exhibited a high polishing rate of more than 3480 Å / min for tungsten wire polishing and 4250 Å / min for copper wire polishing, and 1.6% (tungsten wire polishing) and 1.8% ( Copper wiring polishing).

Example 6

As a metal oxide fine powder, except that ceria was used instead of silica, slurry was prepared in the same manner as in Example 1, and polishing was performed, and polishing performance was evaluated. The evaluation results are shown in Table 1. As shown in Table 1, the slurry composition of Example 6 exhibited high polishing rates of more than 3600 kW / min for tungsten wire polishing and 4300 kW / min for copper wire polishing, and 1.8% (tungsten wire polishing) and 1.7% ( Copper wiring polishing).

Example 7

After leaving the slurry prepared in Example 1 at room temperature for 4 months, polishing was performed in the same manner as in Example 1, and the polishing performance was evaluated. The results are shown in Table 1. From Table 1, in the case of the composition according to the present invention, the polishing rate was maintained at 2910 2 / min at tungsten wire polishing and at 3730 Å / min or higher at copper wiring polishing, even after 4 months of manufacture. It can be seen. Also in the defect rate, it can be seen that the low value is maintained at 1.1% (tungsten wiring polishing) and 1.4% (copper wiring polishing).

Example 8

After the slurry prepared in Example 3 was left at room temperature for 4 months, polishing was performed in the same manner as in Example 1, and the polishing performance was evaluated. The results are shown in Table 1. From Table 1, the composition according to the present invention maintains a relatively high polishing rate even after a time period of 4 months after manufacture, at tungsten wire polishing at 2600 kW / min and copper wiring polishing at 3500 kW / min or more. It can be seen. Also in the defect rate, it can be seen that 1.2% (tungsten wiring polishing) and 1.4% (copper wiring polishing) maintain a low value.

Comparative Example 1

Except that 4-imidazolmethanol was not added in Example 1, slurry was prepared in the same manner as in Example 1 to perform polishing and to evaluate polishing performance. The evaluation results are shown in Table 1. As shown in Table 1, in the case of Comparative Example 1, the polishing rate was maintained relatively high, but the defect rate was high as 2.8 and 3.5.

Comparative Example 2

After the slurry prepared in Comparative Example 1 was left at room temperature for 4 months, polishing was performed and polishing performance was evaluated. The results are shown in Table 1. As shown in Table 1, in Comparative Example 2, not only the polishing rate was significantly lowered but also the defect rate was greatly increased.

According to the present invention, it is possible to prepare a composition for CMP for metal polishing, which is capable of maintaining excellent polishing performance while using a relatively small amount of oxidizing agent, as well as significantly improving chemical and dispersion stability, and having excellent storage stability of the composition. .

Claims (4)

Slurry composition for CMP for metal polishing comprising a metal oxide, hydrogen peroxide water, iron compound, imidazole compound and deionized water. The method of claim 1, wherein the metal oxide is a single oxide or a mixture of two or more oxides selected from the group consisting of silica, aluminum, ceria and titania, the imidazole compound is 4-imidazolmethanol, 4-imidazolethanol And 4-imidazole carboxylic acid alone or a mixture of two or more compounds, wherein the pH of the composition is maintained in the above range using nitric acid or acetic acid. The method according to claim 1 or 2, wherein the metal oxide is 0.1 to 25% by weight, the hydrogen peroxide solution is 1 to 3% by weight, the iron compound is 0.03 to 0.1% by weight based on the total weight of the composition, The imidazole compound is a slurry composition, characterized in that it comprises 0.001 to 0.5% by weight. Iii) preparing a slurry by dispersing the mixture obtained by stirring the metal oxide in an aqueous solution in which iron and acid compounds are dissolved in deionized water and stirring at a temperature of 5 ° C to 30 ° C for a certain time, and ii) hydrogen peroxide and imidazole-based slurry. Method for producing a slurry composition for CMP for metal polishing according to claim 1, characterized in that the compound is added and mixed.