KR20030092605A - Slurry compositions for metal cmp - Google Patents

Abstract

PURPOSE: A polishing slurry composition for metal CMP is provided, to improve the selectivity of copper to oxides and tantalum nitride by a high polishing rate to copper and a low polishing rate to tantalum nitride. CONSTITUTION: The slurry composition comprises 0.2-15 wt% of a polishing agent; 0.5-10 wt% of an oxidizing agent; 0.2-5.0 wt% of a chelator; and the balance of water. The chelator is a carboxylic acid amine. Preferably the chelator is selected from the group consisting of aminoacetic acid, iminodiacetic acid, nitrilotriacetic acid and their salts; the polishing agent is a metal oxide selected from the group consisting of alumina, silica, zirconia, ceria, titania and their mixture; and the oxidizing agent is hydrogen peroxide. Optionally the composition comprises further an antioxidizing agent selected from 5-aminotetrazole and benzotriazole.

Description

Polishing slurry composition for metal CPM {SLURRY COMPOSITIONS FOR METAL CMP}

The present invention relates to a polishing slurry composition which is a chemical solution for forming metal wirings by a chemical mechanical polishing method. More specifically, the present invention relates to a polishing slurry composition for metal CMP, which contains an abrasive, an oxidizing agent, a complexing agent, and any antioxidant.

Integrated circuits consist of hundreds of activators formed in or on a silicon support, where the shorted activators are interconnected to form a functional circuit, with each layer of the activator connected by a multilevel interconnection scheme. do. Interconnect layers in integrated circuits generally have a metallization level connected by a first metal layer, an interconnect layer, a second metal layer, an interconnect layer, and a third metal layer. Dielectrics, such as doped and undoped silicon dioxide (SiO ₂ ), which are used as interconnect layers, are also used to electrically short metal layers at different levels even in silicon supports. In a similar way, the electrical connection between the interconnect level and the device is through a metal layer. Al, Al alloys, W, W alloys and the like can be filled with a metal layer that enables such electrical connection, and copper is being considered as the most promising metal material to be used in the future for interconnection of integrated circuits. Copper has better electron mobility than aluminum and other metal materials that are currently used in the integrated circuit industry, and has a low resistance to significantly improve the performance of integrated circuit devices. Generally, an adhesive layer such as titanium nitride (TiN) or titanium (Ti), tantalum (Ta) or tantalum nitride (TaN) is used to bond the metal layer to the SiO ₂ support, which is an interconnect layer (metal insulating film). The adhesive layer acts as a barrier layer that prevents the reaction between the filled metal and the metal insulating film.

In the chemical mechanical polishing method, a chemical solution (usually expressed as a slurry) is supplied during the polishing process. The slurry facilitates the polishing process by chemically reacting with the film to be polished. The polishing process is accelerated when the slurry is provided at the interface between the wafer and the pad. The slurry is continuously supplied until the film to be polished is removed, and the composition of the slurry serves as an important factor in the CMP process of removing the film to be polished. Depending on which abrasive, oxidant, or additive is selected, the metal insulating film, diffusion wall, or metal layer at a desired polishing rate can be minimized while minimizing important parameters in semiconductor processes such as imperfections, surface roughness, surface defects, erosion and corrosion of the polished surface. Polishing slurry can be prepared that can be effectively polished.

Various mechanisms exist in the prior art in which the metal surface can be polished into a slurry. In the process proceeded by mechanical removal of metal particles in the slurry and their dissolution, the slurry can be polished using a slurry which does not form a surface film. In this mechanism, the chemical dissolution rate must be slow to avoid wet etching. However, a more preferred mechanism is that a thin abrasive layer is formed continuously by reaction of the metal surface with one or more components of the slurry, such as a complexing agent. The thin abrasive film is then removed in a controlled manner by mechanical action. Once the mechanical polishing method is interrupted, a thin passivation film remains on the surface and suppresses the wet etching method. Adjusting the chemical mechanical polishing method can easily remove the metal layer when the CMP slurry is polished using this mechanism.

Regarding the development of copper CMP slurries, the results are described in the literature. J. M. Steigerwald et al., Electrochemical potential measurments during the chemical-mechanical polishing of copper thin films; Res. Soc. Symp. 337,133 (1994) describe the use of ammonium compounds (ammonium nitrate, ammonium chloride, ammonium hydroxide), nitric acid, and alumina abrasives. Copper dissolution (electrochemical measurement) at 2 nm / min is estimated to proceed from the filmless surface, but the polishing rate is reported to be above 400 nm / min. Q. Luo et al., Chemical-mechanical polishing of copper in acidic media, Proceedings-first international chemical-mechanical polish (CMP) for VLS / LSI multilevel interconnection conference (CMP-MIC), Santa Barbara, February 22-23 ( 1996) described the use of CMP slurries with a fairly strong etchant iron nitrate, metal inhibitor benzotriazole, slurry stabilizing surfactant (polyethylene glycol) and alumina. The chemical reaction is clearly inhibited by forming a corrosion inhibiting film, ie, Cu-BTA, with a surfactant that impairs the protective properties of the film. Selectivity to oxide is 15: 1 to 45: 1.

U.S. Pat.No. 5,954,997 and U.S. Pat.No. 6,126,853 describe slurries comprising film forming agents such as benzotriazole, oxidizing agents such as urea hydrogen peroxide, complexing agents such as ammonium oxalate or tartaric acid, abrasives and surfactants, U. S. Patent No. 6,063, 306 describes a slurry comprising an abrasive, an oxidant, a film former, and a complexing agent such as tartaric acid, dodecylamine, and the like. In the case of these slurries, the selectivity of copper and tantalum nitride shows a high selectivity of 7: 1 to 45: 1, but the polishing rate of copper is markedly decreased in production yield at 300 nm / min or less. When the polishing rate of copper is 300 nm / min or more, the polishing rate of tantalum nitride is also large, and it is reported that the selectivity of tantalum nitride to copper is decreasing.

U. S. Patent No. 6,001, 730 describes a slurry comprising carboxylate salt (ammonium citrate) as an oxidizing agent, abrasive, film forming agent and complexing agent, and U. S. Patent No. 6,143, 656 describes an abrasive, oxidizing agent, film forming agent. And a oxalic acid as a complexing agent and a polyether as a surfactant.

Various chemical additives and the like have been applied to find an optimal copper CMP process.However, using these known chemicals, the amount of copper polished and the selectivity to the diffusion barrier layer, and Optimal copper polishing results have not yet been obtained for lotions.

In general, experiments using the above chemicals in copper CMP technology have shown that problems with CMP throughput due to poor copper polishing, device performance and device yield due to corrosion of copper materials, layer planarization problems, One or more defects such as dishing occurring during polishing are generated.

Accordingly, the present inventors have diligently tried to solve these problems, and as a result, by using a slurry composition for metal CMP containing a specific complexing agent, such defects that may occur in metal CMP technology can be solved, It has been found that metal wiring can be produced and the present invention has been completed.

After all, it is an object of the present invention to provide a slurry composition for forming metal interconnects useful for polishing multilevel metallization such as semiconductor thin films, integrated circuit thin films and the like, and useful for CMP processes.

As a means for realizing the present invention, the present invention provides a polishing slurry composition for metal CMP containing an abrasive, an oxidizing agent, a complexing agent and an optional antioxidant.

More specifically, the present invention provides 0.2 to 15% by weight of abrasive, 0.5 to 10% by weight of oxidant, 0.2 to 5.0% by weight of complexing agent, optional antioxidant, and 100% by weight of total composition. It provides a polishing slurry composition for a metal CMP containing water so that the complexing agent is selected from carboxylic acid amines.

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

The composition according to the present invention relates to a CMP slurry composition which is a chemical solution for forming metal wirings by a chemical mechanical polishing method.

The slurry composition according to the present invention comprises an abrasive, an oxidizing agent, a complexing agent and any antioxidant and other additional components, and is useful for polishing multilevel metallization such as semiconductor thin films, integrated circuit thin films, etc., and CMP process is useful metal film. And its surface. The slurry compositions according to the invention are particularly useful for, but not limited to, CMP polishing of copper and copper containing alloys.

The slurry composition according to the present invention contains an abrasive. Metallic oxides are typically used as the abrasive, and the metal oxides may be selected from the group consisting of alumina, silica, zirconia, ceria, titania, and mixtures thereof. Such metal oxides are contained in the slurry composition in the range of about 0.5 to 20% by weight, and are preferably mixed in the aqueous medium in the form of an aqueous dispersion of metal oxides comprising 0.5% to 10% by weight solids. Aqueous dispersions of metal oxides can be prepared using conventional techniques, for example, by the slow addition of metal oxides to a suitable medium (eg, deionized water) to form a colloidal dispersion.

The metal oxides can be produced by the fuming method or the sol-gel method, and the particle size of these metal oxides is 5 to 100 nm, preferably 10 to 60 nm. If the size of the metal oxide is too small, less than 5 nm, it is unfavorable in terms of production yield due to low polishing rate, and when the particle size is 100 nm or more, dispersion is difficult, and it is easy to form large particles by interparticle reaction. It causes a large amount of μ-scratches. In another preferred aspect the metal oxide has a surface area of about 5 m ² / g to about 450 m ² / g, preferably 50 m ² / g to 250 m ² / g, referred to as BET.

The slurry composition according to the present invention contains an oxidizing agent. The oxidant contained in the slurry composition serves to help react with the metal layer and oxidize to the corresponding oxides, hydroxides or ions, for example, it can be used to oxidize tungsten to tungsten oxide and copper to copper oxide. The type of oxidizing agent that can be used is not particularly limited, but hydrogen peroxide (H ₂ O ₂ ) is preferred, and in general, the oxidizing agent used in the slurry is preferably present in the range of about 0.2 to 20% by weight, and about 1.0 to 15 Most preferably present in weight percent. The metal layer chemically oxidized by the oxidant is useful for mechanically polishing to remove the oxide layer.

The slurry composition according to the invention essentially contains one or more complexing agents consisting of carboxylic acid amines, preferably amino acetic acid, imino diacetic acid, nitrile triacetic acid and salts thereof, the complexing agent being It is present in the slurry composition of the present invention in an amount of about 0.2 to about 5% by weight, preferably about 0.3 to 3% by weight. Most preferred complexing agents include imino diacetic acid.

The complexing agent contained in the slurry composition of the present invention plays two or more effective roles. That is, the oxide layer formed by the oxidant is removed by a mechanical method while the oxide layer is removed by the chemical action of the oxide formed on the metal surface and the complexing agent (chelating agent) contained in the slurry. Complexes can be formed to limit the depth of the oxidized layer.

For example, in the case of a Cu film, a copper oxide is formed by an oxidizing agent, and the carboxylic acid amine used as a complexing agent dissolves the copper oxide into Cu ions, and then forms a complex with the generated Cu ions. In addition, the complexing agent may perform a function of controlling the formation of an oxide film by binding to an oxide or the like of the Cu surface to stabilize the Cu surface. Ie Cu → planarization of copper can be achieved by changing to CuO and polishing the changed CuO by mechanical methods.

On the other hand, the complexing agent can function as an etchant, and therefore, the higher the amount of the complexing agent, the higher the etching property, so that the etching of copper can be made too fast, resulting in defects such as dishing or lotion during polishing. You can also adjust the amount.

Therefore, the slurry composition of the present invention may further contain an antioxidant to improve polishing properties. Generally, benzotriazole and triazole derivatives are used as antioxidants, which are compounds containing three nitrogens. In the present invention, one of 5-aminotetrazole (ATZ) or benzotriazole (BTA) containing four nitrogens as an antioxidant is used as the antioxidant, and at least one of these antioxidants is added to the copper CMP slurry. The lower surface can serve to improve the formation of the passivation layer or the dissolution inhibiting layer on the wafer surface, thereby improving the copper planarization. The antioxidant is present in the slurry composition of the present invention in an amount of about 0.001 to 1% by weight, preferably about 0.001 to 0.3% by weight, which is not limited to the above range as an amount that can be changed depending on the amount of the complexing agent. Do not. The reason is that if 0.05 wt% of the antioxidant is applied to 1 wt% of the complexing agent (see Example 2), if the amount of the complexing agent is doubled, the amount of antioxidant should be added twice as much. This is because the effect can be maintained.

The slurry composition of this invention can further contain additives, such as a dispersion stabilizer and a pH control stabilizer, as needed.

According to the present invention, it is advantageous to maintain the pH of the slurry composition in the range of about 2.0 to about 12.0, preferably in the range of about 4.0 to about 9.0, in order to facilitate the control of the CMP process. When the pH of the slurry composition of the present invention is low, for example, less than 2, problems in handling the slurry and problems in polishing the substrate may occur. In particular, when imino diacetic acid is used as the complexing agent, it is preferable to adjust the pH since the CMP precursor and the slurry have a pH of about 2.0.

The adjustment of the pH may use known acids, bases or amines. However, in order to avoid introducing undesirable metal components into the CMP slurry of the present invention, it is preferable to use acids or bases which do not contain metal ions, for example ammonium hydroxide and amines, or nitric acid, sulfuric acid, phosphoric acid and organic acids. It is preferable to use etc.

The slurry composition according to the present invention can be prepared using a conventional production method, and is independent of the mixing order of the chemical composition contained in the slurry.

As a method of dispersing the metal oxide in the slurry composition of the present invention, any conventional dispersion method such as ultrasonic dispersion, milling method, or fluid collision method can be applied.

The slurry compositions of the present invention prepared in this way can be supplied in the form of one composition, such as one composition containing abrasives, oxidants, complexing agents, optional antioxidants, and other additives in a stable medium. In addition, it is possible to produce the CMP slurry composition of the present invention by supplying two or more separate solutions and mixing at a constant rate during the polishing process. At this time, the component may be deteriorated when supplied in the form of one composition, in order to prevent this, it is preferable to be supplied in at least two or more separate solutions, and may be used by mixing at a predetermined ratio immediately before use. . For example, the first solution may be an abrasive (such as alumina), a complexing agent (imino diacetic acid or amino acetic acid, further ammonium citrate may be added), an antioxidant (such as benzotriazole) and other additives It may include a CMP slurry precursor having a range of pH 4.0 to 9.0 containing, the second solution contains hydrogen peroxide.

Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to a following example. The following examples set forth preferred compositions as well as preferred methods for using the compositions of the invention.

All slurry compositions used in the following examples were prepared by separately preparing the first solution containing the components other than the oxidizing agent H ₂ O ₂ , and the second solution containing H ₂ O ₂ in a proportion just before use Used.

Performance evaluation of the prepared slurry composition was performed on a copper blanket wafer having a thickness of about 10000 A (angstroms) using an IC 1400 pad manufactured by Rodel, using a GNP POLI-380F CMP apparatus for 1 minute. Polishing was performed with a descending force of 360 g / cm ² , a table speed of 30 rpm, a head speed of 30 rpm and a slurry flow rate of 100 ml / min.

Example 1

Four polishing slurry compositions containing 3% by weight of alumina, 2.5% by weight of H ₂ O ₂ , 0.1 to 1.0% by weight of varying amounts of imino diacetic acid (IDA), and the remaining deionized water. Was prepared. The effect of the potency and concentration of the complexing agent on the prepared slurry composition was evaluated for the copper blanket wafer, and the results are shown in Table 1.

Composition number H ₂ O ₂ (% by weight) IDA (% by weight) pH Cu Polishing Speed (A / min) One 2.5 0.1 5.2 769 2 2.5 0.3 5.2 3289 3 2.5 0.6 5.2 5278 4 2.5 1.0 5.2 8260

As can be seen from Table 1, in Examples 3 and 4, the copper polishing rate was satisfactory as the Cu polishing rate of 5000 A (angstrom) / min or more, and especially when the IDA content is 1.0% by weight, the Cu polishing rate is The synergistic effect was remarkable as 8000 A / min or more.

Example 2

0.005 to 0.1 wt% of benzotriazole (BTA) or amino tetrazole (5-ATZ) as an antioxidant for copper useful in CMP slurries, with 1.0 wt% of imino diacetic acid relative to the total weight of the composition. 10 kinds of sludge compositions having the same composition as in Example 1 were prepared except that they were contained in various contents. The efficacy of the antioxidants on the prepared slurry compositions was evaluated for copper blanket wafers and the results are shown in Table 2.

Composition number H ₂ O ₂ (% by weight) BTA (% by weight) ATZ (% by weight) pH Cu Polishing Speed (A / min) 5 2.5 0.005 0 5.2 5250 6 2.5 0.01 0 5.2 3735 7 2.5 0.03 0 5.2 1232 8 2.5 0.06 0 5.2 578 9 2.5 0.1 0 5.2 289 10 2.5 0 0.005 5.2 6740 11 2.5 0 0.01 5.2 3670 12 2.5 0 0.03 5.2 2196 13 2.5 0 0.06 5.2 1813 14 2.5 0 0.1 5.2 1388

As can be seen from Table 2, it can be seen that by using an appropriate amount of BTA or ATZ as the antioxidant, the CMP polishing rate can be achieved at 5000 A / min.

Example 3

3 weight percent alumina, 2.5 weight percent H ₂ O ₂ , 0.01 weight percent benzotriazole relative to the total weight of the composition, imino diacetic acid (IDA) and ammonium citrate as complexing agents Five kinds of sludge compositions were prepared. The prepared slurry compositions were evaluated for copper blanket wafers, and the results are shown in Table 3.

Composition number IDA (% by weight) Ammonium Citrate (% by weight) BTA (% by weight) H ₂ O ₂ (% by weight) Cu Polishing Speed (A / min) TaN polishing rate (A / min) 15 0 0.3 0.01 2.5 2200 110 16 0 0.5 0.01 2.5 3000 115 17 1.0 0.3 0.01 2.5 5035 145 18 1.0 0.4 0.01 2.5 5812 128 19 1.0 0.5 0.01 2.5 6325 135

As can be seen from Table 3, Cu (and TaN) polishing rate and Cu: TaN selectivity did not show satisfactory results when ammonium citrate was used alone, but Cu (and TaN) when used with IDA. ) The polishing rate exceeded 5000 A / min, and the Cu: TaN selectivity was over 40: 1, indicating very good Cu selectivity.

Example 4

3% by weight of alumina, 2.5% by weight of H ₂ O ₂ , 1.0% by weight of imino diacetic acid, further comprising 0.01% by weight of BTA and 0.4% by weight of ammonium citrate (composition 20) or Two types of sludge compositions were prepared containing 0.005% by weight of ATZ (composition 21). The pH of the slurry was adjusted to pH 5.2 by addition of ammonium hydroxide. The efficacy of the CMP slurry comprising BTA and ATZ on the copper and tantalum nitride abrasives of the prepared slurry composition was evaluated and the results are shown in Table 4.

Composition number Cu Polishing Speed (A / min) TaN Polishing Speed (A / min) SiO ₂ Polishing Rate (A / min) 20 5812 200 85 21 6417 313 104

As can be seen from Table 4, the Cu polishing rate of the polishing slurry (composition 21) containing ATZ was higher than that of the slurry containing BTA and ammonium citrate (composition 20), and the polishing rate of TaN and oxide film was also high. High in abrasive slurry containing ATZ. Thus, it can be seen that the antioxidant effect can be expected even when using ATZ. Dicing of copper is about 200 A, no lotion occurs, and the selectivity to oxide is high, which is higher than 50: 1, and may act as end-point detection.

The polishing slurry composition for metal CMP according to the present invention is excellent in the selectivity and polishing performance of copper for oxides and tantalum nitride due to the high polishing rate for copper and small polishing rate for tantalum nitride, and the production yield for copper wiring. It is excellent and environmentally safe, so that the treatment of the slurry is easy.

Claims (8)

0.2 to 15 wt% abrasive, 0.5 to 10 wt% oxidant, 0.2 to 5.0 wt% complexing agent, and water so that the total composition total weight is 100 wt% based on the total weight of the total composition, the complexing agent being carbon Polishing slurry composition for metal CMP selected from acidic amines. The slurry composition of claim 1 further comprising an antioxidant selected from 5-aminotetrazole (ATZ) and benzotriazole (BTA). The slurry composition of claim 1 or 2, wherein the pH of the composition is from about 2 to 12. A slurry composition according to claim 1 or 2, wherein the complexing agent is selected from the group consisting of amino acetic acid, imino diacetic acid, nitrilo triacetic acid and salts thereof. 5. The slurry composition of claim 4, wherein the complexing agent is imino diacetic acid. 3. The slurry composition of claim 1 or 2, wherein the abrasive is a metal oxide selected from the group consisting of alumina, silica, zirconia, ceria, titania, and mixtures thereof. 7. The slurry composition of claim 6, wherein the abrasive is alumina. The slurry composition of claim 1 or 2, wherein the oxidant is hydrogen peroxide.