KR100738842B1 - Polishing composition and polishing method employing it - Google Patents

Abstract

The present invention relates to a polishing composition containing the following components:

(a) abrasive,

(b) α-alanine,

(c) hydrogen peroxide, and

(d) water.

Polishing composition, semiconductor device, copper layer, tantalum-containing compound layer

Description

Polishing composition and polishing method using the same {POLISHING COMPOSITION AND POLISHING METHOD EMPLOYING IT}

The present invention provides polishing compositions for use in polishing substrates for semiconductors, photomasks and various memory hard disks, in particular polishing compositions useful for polishing for planarization of the surface of device wafers, for example in the semiconductor industry, and It relates to a polishing method using such a composition.

More specifically, the present invention relates to a polishing composition which provides a highly effective and high selectivity in the polishing of semiconductor devices in which so-called chemical mechanical polishing (CMP) technology is used, the processing of device wafers, and a polishing method using the composition. will be.

Recently, the development of so-called high-tech products, including computers, is remarkable, and members for use in such products, for example ULSI, have been developed year by year for high integration and high speed. With this development, the design rules for semiconductor devices have been gradually improved year by year, the depth of focus in the manufacturing method of the device tends to be shallow, and the planarization required for the pattern forming surface becomes more difficult. have.

In addition, in order to cope with an increase in wiring resistance due to polishing of wiring, it has been studied to use copper as a wiring material instead of tungsten or aluminum.

Copper is difficult to process by etching due to its properties, and therefore requires the following process. That is, after the wiring grooves and vias are formed on the insulating layer, the copper wiring is formed by sputtering or plating, and then the unnecessary copper layer deposited on the insulating layer is mechanically polished. And mechanical chemical polishing (hereinafter referred to as CMP), which is a combination of chemical polishing.

However, in such a method, copper atoms may diffuse into the insulating layer and degrade device characteristics. Therefore, in order to prevent the diffusion of copper atoms, it has been studied to provide a barrier layer on the wiring groove and the insulating layer formed of the length. As the material of this barrier layer, metal tantalum or tantalum compounds (hereinafter commonly referred to as tantalum-containing compounds) are also most suitable in terms of reliability of the device, and are expected to be used mostly in the future.

Thus, in the CMP process of the semiconductor device including the copper layer and the tantalum compound, first the copper layer as the outermost layer, and then the tantalum-containing compound layer as the barrier layer, respectively, are polished, for example, silicon dioxide. Or when the insulating layer of monofluorosilicon oxide (SiOF) is reached. As an ideal process, it is desirable to uniformly remove the copper layer and tantalum-containing compound layer by polishing by a single polishing step by using only one type of polishing composition, and the polishing ends reliably when the insulating layer is reached. However, copper and tantalum-containing compounds differ in their hardness, chemical stability and other mechanical properties, and thus also in workability, and therefore, it is difficult to adopt such an ideal polishing process. Therefore, the following two-step polishing process, that is, a polishing process divided into two stages is being studied.

First, in the first polishing step (hereinafter referred to as first polishing), a polishing composition capable of polishing the copper layer with high efficiency, for example, using a tantalum-containing compound layer as a stopper Thereby polishing the copper layer until it reaches the tantalum-containing compound layer. Here, just before the tantalum-containing compound layer is reached, i.e., the copper layer is still on, for the purpose of avoiding the formation of various surface damages, for example recesses, corrosion, dishing, etc., on the copper layer surface. Polishing can be terminated while slightly remaining. Then, in the second step polishing (hereinafter referred to as second polishing), the remaining copper thin layer and tantalum-containing compound layer are stopper, using a polishing composition capable of polishing the tantalum-containing layer mainly with high efficiency. As a result, polishing is continued using the insulating layer, and the polishing ends when the insulating layer is reached.

The polishing composition for use in the first polishing has the property of being able to polish the copper layer at a high stock removal rate without forming the various surface defects on the copper layer surface, which cannot be removed by the second polishing. It is required to have.

In connection with such polishing compositions for copper layers, for example, JP-A-7-233485 includes polishing liquids for copper-type metal layers, wherein the layer is at least one organic acid, oxidizing agent selected from the group consisting of aminoacetic acid and amidsulfuric acid. And water), and a method of manufacturing a semiconductor device using such a polishing liquid. When such polishing liquid is used for polishing the copper layer, a relatively high stock removal rate can be obtained. It is contemplated that copper atoms on the copper layer surface should be oxidized by the action of an oxidant, and that the oxidized copper element becomes a chelate compound so that a high stock removal rate can be obtained.

However, as a result of experiments conducted by the inventors, when the polishing liquid is used to polish a semiconductor device having a copper layer and a tantalum-containing compound layer, the stock removal rate of the copper layer relative to the stock removal rate of the tantalum-containing compound layer The ratio of (hereinafter referred to as "selectivity") is inadequate, and it has been found that if the composition or the like is adjusted to increase the selectivity, the smoothness of the surface of the copper layer after polishing tends to be significantly impaired. That is, the polishing liquid has problems with the selectivity and smoothness of the polishing surface and still needs to be further improved.

The present invention is to solve the above problems. That is, an object of the present invention is to provide a polishing composition and a polishing method, so that in a CMP process in the manufacture of a semiconductor device having at least one copper layer and a tantalum-containing compound layer, a high selectivity can be provided (ie copper High stock removal rate of the layer and low stock removal rate of the tantalum-containing compound layer), and smoothness to provide an excellent polishing surface.

The present invention provides a polishing composition containing the following components:

(a) abrasive,

(b) α-alanine,                     

(c) hydrogen peroxide, and

(d) water.

The present invention also provides a polishing method for polishing a semiconductor device in which a copper layer and a tantalum-containing compound layer are formed on a substrate, using a polishing composition containing the following components:

(a) abrasive,

(b) α-alanine,

(c) hydrogen peroxide, and

(d) water.

According to the present invention, in a CMP process for a semiconductor device having at least one copper layer and a tantalum-containing compound layer, a high selectivity ratio, that is, a high stock removal rate of the copper layer and a low stock removal rate of the tantalum-containing compound layer, can be provided. And a polishing surface with excellent smoothness can be provided.

In addition, according to the present invention, in the production of the semiconductor device, the semiconductor device can be manufactured with excellent yield.

In the polishing composition of the present invention, the abrasive has a role as so-called polishing grain and functions to perform mechanical polishing in CMP processing. That is, the abrasive has the effect of mechanically removing a brittle layer formed on the surface to be polished by various compound components described below.

The polishing composition of the present invention contains at least one member selected from the group consisting of silicon dioxide, aluminum oxide, cerium oxide, titanium oxide, silicon nitride, zirconium oxide, silicon carbide and manganese dioxide as an abrasive.

Among these, silicon dioxide includes colloidal silica, fumed silica, and many other forms having different properties or manufacturing methods.

Aluminum oxide also includes α-alumina, δ-alumina, θ-alumina, κ-alumina and other morphologically different ones. In addition, there is also a so-called fumigated alumina from the production method thereof.

The cerium oxide includes trivalent and tetravalent ones from its oxidation value, and includes hexagonal, equiaxed, and face centered cubic systems from its crystal system.

Zirconium oxide includes monoclinic, tetragonal and amorphous forms from its crystal system. In addition, there is a so-called fumigation zirconia from its production method. In addition, so-called partially stabilized zirconia, in which calcium, magnesium or yttrium solids are solubilized, which stabilizes the crystalline portion as the cubic system, and fully stabilized zirconia with an increased amount of solid stabilization of these elements to fully stabilize all crystals as the cubic system. There is.

Titanium dioxide includes titanium monoxide, dititanium trioxide, titanium dioxide and other types from its crystal system. In addition, there is a so-called fumigation titania from its production method.

Silicon nitride includes α-silicon nitride, β-silicon nitride, amorphous silicon nitride and other morphologically different ones.                     

Silicon carbide includes α- and β-forms.

Manganese dioxide includes other morphologically different from α-manganese dioxide, β-manganese dioxide, γ-manganese dioxide, δ-manganese dioxide, ε-manganese dioxide, η-manganese dioxide and forms thereof.

In the polishing composition of the present invention, the abrasive may be optionally mixed and used if necessary. In the case of blending and using an abrasive, the blending method or the proportion thereof is not particularly limited.

The abrasive preferably uses a colloidal abrasive having a small particle size and uniformity in order to reduce the precipitation of the abrasive in the polishing composition during storage and to prevent scratches due to the abrasive from forming on the object to be polished. That is, when using silicon dioxide, fumed silica and / or colloidal silica is preferred, and when using alumina, fumed alumina and / or colloidal alumina is preferred.

The abrasive is for polishing a surface to be polished by mechanical action. Among them, the particle size of silicon dioxide or aluminum oxide is, as a mean particle size observed with a scanning electron microscope, generally 0.01 to 0.2 μm, preferably 0.015 to 0.1 μm. Likewise, the particle size of cerium oxide, zirconium oxide, titanium oxide, silicon nitride, silicon carbide or manganese dioxide is an average particle size observed by scanning electron microscopy, generally from 0.03 to 0.3 μm, preferably 0.05 to 0.2 μm.

If the primary particle size of the abrasive is too large, the mechanical polishing action is too high to increase the degree of polishing of the tantalum-containing compound layer, which tends to form scratches during polishing. On the other hand, when the primary particle size is too small, the mechanical removal action tends to decrease, thereby decreasing the stock removal rate of the copper layer.

The content of the abrasive in the polishing composition of the present invention is generally 10 to 200 g / l, preferably 30 to 100 g / l. If the content of the abrasive is too small, the mechanical polishing force may be reduced, thereby reducing the stock removal rate of the copper layer. On the other hand, when the content of the abrasive is too high, the mechanical polishing force increases, and the polishing rate of the tantalum-containing compound layer tends to be too large to be difficult to control.

α-alanine

The polishing composition of the present invention contains α-alanine. α-alanine has an optical isomer, and in the case of the polishing composition of the present invention, any of D-type, L-type, or DL-type can be used.

The content of α-alanine in the polishing composition of the present invention is generally 0.02 to 0.20 mol / l, preferably 0.05 to 0.15 mol / l. When the content of α-alanine is too small, the stock removal rate of the copper layer tends to be small. On the other hand, when the content is too large, the stock removal rate of the copper layer becomes too large to be difficult to control, so that the smoothness of the surface of the copper layer after polishing tends to be poor.

Alanine also includes β-alanine as an isomer. β-alanine is structurally different from α-alanine and is not believed to provide the same function as α-alanine in the polishing composition of the present invention. However, in the polishing composition of the present invention, β-alanine may be contained in the polishing composition of the present invention without impairing the effects of the present invention. In general, mixtures of α-alanine and β-alanine are cheap compared to pure α-alanine, and in terms of cost, it is preferable for industrial use to use such mixtures. However, even in the above case, the content of α-alanine is preferably within the above range. Therefore, when using a mixture of α-alanine and β-alanine, the content of the alanine mixture should be determined in consideration of the blend ratio.

Hydrogen peroxide

The polishing composition of the present invention contains hydrogen peroxide. In the polishing composition of the present invention, hydrogen peroxide is considered to act as an oxidizing agent. Here, hydrogen peroxide has sufficient oxidizing power to oxidize the copper layer and has a property which can be easily obtained as containing no metal ions as impurities at all, and is particularly suitable for the polishing composition of the present invention.

The content of hydrogen peroxide in the polishing composition of the present invention is generally from 0.01 to 1 mol / l, preferably from 0.05 to 0.3 mol / l, more preferably from 0.08 to 0.15 mol / l. If the content of hydrogen peroxide is too little or too much, the stock removal rate of the copper layer tends to be small, so proper care is required accordingly.

water

The medium of the polishing composition of the present invention is water. It is desirable that the water be reduced in impurities as much as possible so that each of the components can perform their role accurately. In other words, the water is preferably distilled water or ion exchange resin to remove the ionic impurities and the filter is suspended.

Polishing composition

The polishing composition of the present invention is generally prepared by mixing, dissolving or dispersing each of the above components, that is, abrasive, α-alanine and oxidizing agent in water. Here, the mixing, dissolving or dispersing method is optional. For example, stirring or ultrasonic dispersion by a vane type stirrer may be used. In this way, the soluble component is dissolved and the insoluble component is dispersed to give a homogeneous dispersion of the composition.

The polishing composition of the present invention may further contain a corrosion inhibitor, a pH adjusting agent for adjusting pH, various surfactants and other additives as necessary.

A corrosion inhibitor is for suppressing the etching action to a copper layer. By this effect, it is possible to suppress the reduction of the copper layer due to the formation of surface defects such as recesses, dishing or erosion during polishing. As the corrosion inhibitor that can be used in the polishing composition of the present invention, any corrosion inhibitor can be used as long as it can suppress the etching action on the copper layer. In general, benzotriazole, tolyltriazole, benzimidazole, triazole, imidazole and the like can be mentioned. Among these, benzotriazole or tolyltriazole is preferable. The amount of incorporation of the preservative depends on the type of preservative used, but is generally from 0.005 to 0.0012 mol / l. The addition of corrosion inhibitors to the polishing compositions of the present invention can sometimes reduce the stock removal rate. Therefore, due care should be taken in the selection of its type and content.

In the present invention, a pH adjuster is used to improve the stability of the polishing composition, to improve the stability in use, or to meet the requirements of various regulations. Examples of pH adjusting agents used to lower the pH of the polishing composition of the present invention include hydrochloric acid, nitric acid, sulfuric acid, chloroacetic acid, tartaric acid, succinic acid, citric acid, malic acid, malonic acid, various fatty acids, various polycarboxylic acids, and the like. . On the other hand, those used for the purpose of increasing the pH include potassium hydroxide, sodium hydroxide, ammonia, ethylenediamine, piperazine, polyethyleneimine and the like. The polishing composition of the present invention is not particularly limited in terms of pH, but is generally adjusted to a pH of 3 to 10.

In the polishing composition of the present invention, a surfactant is used to increase the dispersibility of the abrasive or to adjust the interfacial tension or viscosity of the polishing composition. As surfactant, a dispersing agent, a wetting agent, a thickener, an antifoamer, a foaming agent, a waterproofing agent, etc. are mentioned, for example. Surfactants used as dispersants may generally be of sulfonic acid type, phosphoric acid type, carboxylic acid type or nonionic acid type.

In the preparation of the polishing composition of the present invention, there is no particular limitation in terms of mixing order or mixing method of various additives.

The polishing compositions of the present invention can be prepared, stored or transported in the form of relatively high concentration stock solutions and can be diluted for use in actual polishing operations. The preferred concentration range is for the actual polishing operation. Needless to say, when employing such a method of use, the stock solution during storage or transport is a higher concentration solution.

Hydrogen peroxide also has the property of decomposing in the presence of metal ions, ammonium ions or amines. Therefore, in the polishing composition of the present invention, it is recommended to add and mix hydrogen peroxide to the polishing composition immediately before actual use in the polishing operation. Such decomposition of hydrogen peroxide can be suppressed by incorporation of carboxylic acid or alcohol molecules. That is, this effect can be obtained with the pH adjusting agent. However, the decomposition is also affected by the storage environment, and there is a possibility that some of the hydrogen peroxide is decomposed due to temperature change or stress formation during transport. Therefore, it is preferable to mix hydrogen peroxide immediately before polishing.

Polishing mechanism

While the polishing composition of the present invention provides a low stock removal rate of the tantalum-containing compound layer, it provides a high selectivity by providing a high stock removal rate of the copper layer, thereby obtaining a polishing surface with excellent smoothness. The polishing mechanism is not clearly known, but may be explained as follows.

First, α-alanine is believed to provide a high stock removal rate of the copper layer by forming chelate bonds to copper during polishing. On the other hand, although glycine, which has been used in the prior art, also exhibits a chelating action on the copper layer, such action is so strong that the stock removal rate of the tantalum-containing compound layer is too large to obtain a suitable selectivity. Moreover, the smoothness of the copper film surface after polishing also tends to be impaired. That is, α-alanine contains an amino group and a carboxyl group at the α-position, which provides a chelating effect, but likewise a tantalum-containing compound by having a methyl group present in the α-position having a function of modulating the effects of the carboxyl and amino groups The stock removal rate of the film is suppressed and the smoothness of the copper film surface after polishing is not lost. It should be understood from this mechanism that β-alanine does not provide the effect of the present invention.

In addition, in the polishing composition of the present invention, hydrogen peroxide is considered to provide an oxidation action. This action is used in conventional CMP processing. In the present invention, however, polishing is more effectively promoted by a combination of the chelating effect by α-alanine and the oxidation action of hydrogen peroxide. Therefore, the stock removal rate of the copper layer is maximized when their balance is optimized. Therefore, the stock removal rate tends to be small when the content of hydrogen peroxide is too much or too little.

It is also contemplated that corrosion inhibitors that can be used in the polishing compositions of the present invention provide the function of adsorbing harder on the copper film surface than α-alanine to protect the copper film surface. Therefore, the etching effect on the copper layer can be suppressed and a surface excellent in smoothness can be obtained.

When the polishing composition of the present invention is used for polishing a solid printing layer (only a wafer having a copper or tantalum-containing compound layer is formed), the stock removal rate of the copper layer is usually at least 4,000 kPa / min, for example polishing By optimizing the composition, it can be made at least 5,000 kPa / min. On the other hand, the stock removal rate of the tantalum-containing compound layer is usually 200 kPa / min or less, and can be made to be 100 kPa / min or less by optimizing polishing conditions. Thus, the copper layer can be polished at a high stock removal rate, while the tantalum compound layer can be polished at a low stock removal rate. When this is represented by a selection ratio, this selection ratio is usually 20 or more, and can be made to be 50 or more by optimizing polishing conditions. This high selectivity facilitates detection of the final point of polishing, and high yields can be achieved. In addition, with the polishing composition of the present invention, polishing can be performed with high efficiency while maintaining excellent surface smoothness, so that high throughput can be realized.

The present invention will now be described in more detail with reference to examples. However, it should be understood that the present invention is in no way limited by these embodiments.

Examples 1 to 27, and Comparative Examples 1 and 2

Preparation of Abrasive Composition

Colloidal silica, hydrogen peroxide and α-alanine or glycine as abrasives were added and mixed in the ratio as shown in Table 1 to obtain the polishing compositions of Examples 1 to 27 and Comparative Examples 1 and 2. Using a commercially available 31% aqueous solution as hydrogen peroxide, it was mixed just before polishing.

Polishing test

As the object to be polished, a 15.24 cm (6 inch) silicon wafer with a copper layer formed to a thickness of about 10,000 mm by sputtering and a 6 inch silicon wafer with a tantalum layer formed to a thickness of about 2,000 mm by sputtering were used, respectively. The surface on which the layer of the wafer was formed was polished.

Polishing was performed using a machine that polished one side (table diameter: 570 mm). A laminated polishing pad made of polyurethane (IC-1000 / Suba400, manufactured by Rodel Inc., USA) was bonded to the table of the polishing machine. First, the wafer with a copper layer was put on and polished for 1 minute, and then it was changed to a wafer with a tantalum layer and similarly polished for 1 minute. The polishing conditions were that the polishing pressure was 490 g / cm ² , the table rotational speed was 40 rpm, the feeding rate of the polishing composition was 50 cc / min, and the rotational speed of the wafer was 40 rpm.

After polishing, the wafers were washed and dried sequentially, at which time the stock removal rate in each test was obtained by measuring the thickness reduction of the layer of each wafer by polishing at 49 points. In addition, the polishing surface after polishing was observed with an optical microscope, and the surface state after polishing was evaluated according to the following standard:

◎: excellent

O: Slightly damaged smoothness

△: smoothness is partially damaged

X: Corrosion is observed on the surface and the smoothness is inferior

XX: Corrosion is very serious and smoothness is very poor in actual use

The results obtained are shown in Table 1 together with the composition of the polishing composition.                     

Abrasive (g / ℓ) Hydrogen peroxide (mol / ℓ) Additive (mol / l) Stock removal rate (Å / min) Selectivity Surface condition after polishing Cu Ta Example 1 C1 ^* 5 0.1 A ^* 0.1 2,000 21 95.2 ◎ Example 2 C1 10 0.1 A 0.1 3,068 31 99.0 ◎ Example 3 C1 30 0.1 A 0.1 4,903 60 81.7 ◎ Example 4 C1 100 0.1 A 0.1 7,347 126 58.3 ◎ Example 5 C1 200 0.1 A 0.1 8,185 207 39.5 ◎ Example 6 C1 250 0.1 A 0.1 8,385 241 34.8 ◎ Example 7 C1 50 0.005 A 0.1 493 76 6.5 ◎ Example 8 C1 50 0.01 A 0.1 2,030 79 25.7 ◎ Example 9 C1 50 0.03 A 0.1 4,056 81 50.1 ◎ Example 10 C1 50 0.05 A 0.1 5,017 82 61.2 ◎ Example 11 C1 50 0.1 A 0.1 5,814 83 70.0 ◎ Example 12 C1 50 0.15 A 0.1 5,757 83 69.4 ◎ Example 13 C1 50 0.3 A 0.1 4,990 77 64.8 ◎ Example 14 C1 50 1.0 A 0.1 3,659 82 44.6 O Example 15 C1 50 1.5 A 0.1 3,233 78 41.4 △ Example 16 C1 50 0.1 A 0.01 984 61 16.1 ◎ Example 17 C1 50 0.1 A 0.02 1,986 68 29.2 ◎ Example 18 C1 50 0.1 A 0.05 4,530 71 63.8 ◎ Example 19 C1 50 0.1 A 0.15 6,915 80 86.4 ◎ Example 20 C1 80 0.1 A 0.2 7,104 83 85.6 O Example 21 C1 80 0.1 A 0.25 7,408 79 93.8 △ Example 22 C2 ^* 80 0.1 A 0.1 3,918 62 63.2 ◎ Example 23 C3 ^* 5 0.1 A 0.1 4,800 73 65.7 ◎ Example 24 C4 ^* 5 0.1 A 0.1 5,371 77 69.6 ◎ Example 25 C5 ^* 5 0.1 A 0.1 6,066 89 68.2 ◎ Example 26 C6 ^* 5 0.1 A 0.1 6,444 21 70.0 ◎ Example 27 C7 ^* 5 0.1 A 0.1 5,814 94 61.9 O Comparative Example 1 C1 50 0.1 G ^* 0.1 3,500 200 17.5 X Comparative Example 2 C1 50 0.3 G 0.1 8,000 200 40.0 XX

Abrasives:

    C1: colloidal silica (primary particle size: 0.03 μm)

    C2: colloidal silica (primary particle size: 0.005 μm)

    C3: colloidal silica (primary particle size: 0.01 μm)

    C4: colloidal silica (primary particle size: 0.015 μm)

    C5: colloidal silica (primary particle size: 0.1 μm)                     

    C6: colloidal silica (primary particle size: 0.2 μm)

    C7: colloidal silica (primary particle size: 0.3 μm)

additive:

    A: α-alanine

    G: glycine

From the results shown in Table 1, in the case of the polishing composition of the present invention, the stock removal rate of the copper (Cu) layer is large, while the stock removal rate of the tantalum (Ta) film is small, the selectivity is large, and at the same time, Smoothness is evident.

According to the present invention, in a CMP process of a semiconductor device including at least a copper layer and a tantalum-containing compound layer, the stock removal rate of the copper layer is increased while the stock removal rate of the tantalum-containing compound is reduced to provide a large selectivity. It is possible to obtain a polishing surface with excellent smoothness. Moreover, according to this invention, the semiconductor device excellent in the yield can be provided in manufacture of the said semiconductor device.

Claims (13)

As a polishing composition for polishing a semiconductor device in which a copper layer and a tantalum-comprising compound layer containing the following components are formed on a substrate: (a) an abrasive in the form of silica, (b) α-alanine, (c) hydrogen peroxide, (d) preservatives, and (e) water: The primary particle size of the abrasive is 0.01 to 0.3 μm, The polishing composition wherein the content of α-alanine is 0.01 to 0.25 mol / l based on the polishing composition, and the content of hydrogen peroxide is 0.01 to 1.5 mol / l based on the polishing composition. delete The polishing composition of claim 1, wherein the abrasive is at least one member selected from the group consisting of fumed silica and colloidal silica. The polishing composition of claim 1, wherein the content of the abrasive is 10 to 200 g / l based on the polishing composition. The polishing composition according to claim 1, wherein the content of α-alanine is 0.02 to 0.2 mol / l based on the polishing composition, and the content of hydrogen peroxide is 0.01 to 1 mol / l based on the polishing composition. delete As a polishing method for polishing a semiconductor device in which a copper layer and a tantalum-comprising compound layer are formed on a substrate using a polishing composition containing the following components: (a) an abrasive in the form of silica, (b) α-alanine, (c) hydrogen peroxide, and (d) water: The primary particle size of the abrasive is 0.01 to 0.3 μm, the content of α-alanine is 0.01 to 0.25 mol / l based on the polishing composition and the content of hydrogen peroxide is 0.01 to 1.5 mol / l based on the polishing composition. 8. The method of claim 7, wherein the amount of abrasive is 10 to 200 g / l based on the polishing composition. 8. The method of claim 7, wherein the content of α-alanine is 0.02 to 0.2 mol / l based on the polishing composition and the content of hydrogen peroxide is 0.01 to 1 mol / l based on the polishing composition. The polishing composition according to claim 1, wherein the corrosion inhibitor is benzotriazole, tolyltriazole, benzimidazole, triazole or imidazole. A polishing method for polishing a semiconductor device in which a copper layer and a tantalum-comprising compound layer are formed on a substrate using the polishing composition according to any one of claims 1, 3 to 5 and 10. 8. The method of claim 7, wherein the abrasive is at least one member selected from the group consisting of fumed silica and colloidal silica. 8. The method of claim 7, wherein the polishing composition further comprises a corrosion inhibitor selected from benzotriazole, tolyltriazole, benzimidazole, triazole or imidazole.