JP4759779B2 - Substrate polishing method - Google Patents

Description

【００２９】
【表２】

【００３０】
実施例１は、砥粒と水溶性高分子を配合しない例で、酸化剤である過酸化水素濃度を第１の工程では９重量％含む研磨液で研磨し、第２の工程では、過酸化水素を０．１５重量％含む研磨液で研磨する例である。第１の工程で使用する研磨液中の過酸化水素濃度を高くすると銅の研磨速度が２１０ｎｍ／ｍｉｎとバリアであるタンタルの０．３ｎｍ／ｍｉｎに比べ顕著に速くなる。一方、第２の工程で使用する研磨液中の過酸化水素を０．１５重量％とすると銅の研磨速度が１７．０ｎｍ／ｍｉｎとバリアであるタンタルの４．５ｎｍ／ｍｉｎと銅の研磨速度が遅くなり、タンタルの研磨速度が速くなる。絶縁層である二酸化シリコンの研磨速度は、非常に小さい。銅とバリアのタンタルの研磨速度は、砥粒を配合した実施例２、さらに水溶性高分子を配合した実施例３においてもその傾向は変化がない。二酸化シリコンの絶縁層に溝を形成し、銅の拡散を防止するバリア層としてタンタルを用いて、その表面に銅層を設けた場合、第１の工程で酸化剤である過酸化水素の濃度を高めた研磨液を使用すると、銅層の研磨速度が速く、短時間に研磨することができ、銅層が研磨されてバリア層が露出してくる。バリア層が露出してきたら、今度は、第２の工程で研磨液として、酸化剤である過酸化水素濃度を低下させ、研磨すると、銅の研磨速度が低下し、タンタルの研磨速度が速くなり、バリア層と銅層をほぼ同じ程度に研磨できるようになる。このように第１の工程で、酸化剤である過酸化水素濃度の高い研磨液をポンプ等で供給し、バリア層が露出してきたら、第２の工程として過酸化水素の濃度の低い研磨液をポンプ等で供給し研磨すると良い。絶縁層である二酸化シリコンの研磨速度は銅やタンタルに比べ低く、研磨はこの層の上面付近で確実に停止できる。
【００３１】
【発明の効果】
本発明の基板の研磨方法は、研磨液のｐＨが３よりも小さく、かつ酸化剤の濃度を第１工程の銅または銅合金の研磨では１．５〜１０重量％に、第２工程のバリア層の研磨では０．０１〜３重量％に調整することにより、酸化剤濃度を変えるだけで、１つの研磨定盤で、銅または銅合金膜の研磨とバリア層の研磨を連続して効率的に行うことができ、信頼性の高い金属膜の埋め込みパタ−ン形成が可能になる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for polishing a substrate used for polishing a wiring formation process of a semiconductor device.
[0002]
[Prior art]
In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (hereinafter referred to as LSIs). The chemical mechanical polishing (hereinafter referred to as CMP) method is one of them, and is a technique frequently used in the LSI manufacturing process, particularly in the multilayer wiring formation process, planarization of the interlayer insulating film, metal plug formation, and buried wiring formation. . This technique is disclosed, for example, in US Pat. No. 4,944,836.
[0003]
Recently, in order to improve the performance of LSIs, the use of copper or copper alloys as wiring materials has been attempted. However, it is difficult to finely process copper or a copper alloy by a dry etching method frequently used in the formation of a conventional aluminum alloy wiring. Therefore, a so-called damascene method is mainly used, in which a copper or copper alloy thin film is deposited and embedded on an insulating film in which a groove is formed in advance, and a copper or copper alloy thin film other than the groove is removed by CMP to form a buried wiring. It has been adopted. This technique is disclosed, for example, in JP-A-2-278822.
[0004]
A general method of metal CMP such as copper or copper alloy is a surface on which a polishing pad is pasted on a circular polishing platen (platen), the surface of the polishing pad is immersed in a metal polishing liquid, and a metal film of a substrate is formed. Is pressed and a polishing surface plate is rotated with a predetermined pressure (hereinafter referred to as polishing pressure) applied from the back surface, and the metal film on the convex portion is removed by mechanical friction between the polishing liquid and the convex portion of the metal film. Is.
The metal polishing liquid used in CMP is generally composed of an oxidizing agent and solid abrasive grains, and a metal oxide dissolving agent and a protective film forming agent are further added as necessary. First, it is considered that the basic mechanism is to oxidize the surface of a metal film with an oxidizing agent and scrape the oxidized layer with solid abrasive grains. Since the oxide layer on the metal surface of the concave portion does not touch the polishing pad so much and the effect of scraping off by the solid abrasive grains is not exerted, the metal layer of the convex portion is removed and the substrate surface is flattened with the progress of CMP. The details are disclosed in Journal of Electrochemical Society, Vol. 138, No. 11 (published in 1991), pages 3460-3464.
[0005]
As a method for increasing the polishing rate by CMP, it is effective to add a metal oxide dissolving agent. It can be interpreted that the metal oxide particles scraped off by the solid abrasive grains are dissolved in the polishing liquid (hereinafter referred to as etching) because the effect of scraping off by the solid abrasive grains is increased. Although the polishing rate by CMP is improved by adding a metal oxide solubilizer, on the other hand, when the oxide layer on the metal film surface in the recess is also etched (dissolved) and the metal film surface is exposed, the metal film surface is further oxidized by the oxidant. If this is repeated, etching of the metal film in the recesses proceeds. For this reason, a phenomenon occurs in which the central portion of the surface of the metal wiring embedded after polishing is depressed like a dish (hereinafter referred to as “dicing”), and the planarization effect is impaired.
[0006]
In order to prevent this, a protective film forming agent is further added. The protective film forming agent forms a protective film on the oxide layer on the surface of the metal film and prevents dissolution of the oxide layer in the polishing liquid. This protective film can be easily scraped off by solid abrasive grains, and it is desirable not to decrease the polishing rate by CMP.
In order to suppress corrosion during dishing and polishing of copper and copper alloys, and to form highly reliable LSI wiring, benzotriazole (as metal oxide solubilizer and protective film forming agent consisting of aminoacetic acid or amide sulfuric acid such as glycine) A method using a metal polishing liquid containing BTA) has been proposed. This technique is described in, for example, JP-A-8-83780.
[0007]
In metal embedding formation such as damascene wiring formation of copper or copper alloy or plug wiring formation of tungsten, etc., when the polishing rate of the silicon dioxide film that is an interlayer insulating film formed other than the embedded portion is high, the interlayer insulating film Thinning in which the thickness of each wiring is reduced occurs. As a result, resistance variation occurs due to an increase in wiring resistance, pattern density, and the like, so that a characteristic in which the polishing rate of the silicon dioxide film is sufficiently small with respect to the metal film to be polished is required. Accordingly, a method has been proposed in which the polishing rate of silicon dioxide is suppressed by anions generated by acid dissociation so that the polishing solution has a pH higher than pKa-0.5. This technique is described in, for example, Japanese Patent No. 2819196.
[0008]
On the other hand, tantalum, a tantalum alloy, tantalum nitride, other tantalum compounds, and the like are formed as barrier layers to prevent copper diffusion into the interlayer insulating film under the copper or copper alloy layer of the wiring. Therefore, it is necessary to remove the exposed barrier layer by CMP except for the wiring portion in which copper or copper alloy is embedded. However, since these barrier layer conductor films have higher hardness than copper or copper alloy, a combination of polishing materials for copper or copper alloy cannot often provide a sufficient polishing rate. Therefore, a two-step polishing method is being studied which includes a first step of polishing copper or a copper alloy and a second step of polishing the barrier layer conductor.
[0009]
In the two-stage polishing method comprising the first step of polishing copper or copper alloy and the second step of polishing the barrier layer, the hardness and chemical properties of the film to be polished are different. Regarding compositions such as additives, those having considerably different properties have been studied.
[0010]
[Problems to be solved by the invention]
Tantalum, tantalum alloys, tantalum nitride, and other tantalum compounds used as barrier layers are chemically stable and difficult to etch, and have high hardness, so mechanical polishing is not as easy as copper or copper alloys. Therefore, if the hardness of the abrasive grains is increased, polishing scratches may occur in the copper or copper alloy, resulting in poor electrical characteristics, or if the abrasive grain concentration is increased, the silicon dioxide film is polished. There was a problem that the speed increased and thinning occurred.
The present invention provides a method for polishing a substrate, which can efficiently polish copper or a copper alloy and a barrier layer conductor continuously and enables a highly reliable embedded pattern of a metal film to be formed. Is.
[0011]
[Means for Solving the Problems]
The substrate polishing method of the present invention includes a first step of polishing and planarizing copper or a copper alloy using a polishing liquid containing an oxidizing agent for a conductor, a protective film forming agent for a metal surface, an acid and water. In the polishing method comprising the second step of polishing the barrier layer under the copper or copper alloy, the substrate polishing method is characterized in that polishing is performed by changing the concentration of the oxidizing agent.
The oxidizing agent concentration of the polishing liquid is preferably 1.5 to 10 parts by weight in the first step, and 0.01 to 3% by weight in the second step, and the oxidizing agent concentration of the polishing liquid is set to the first step. In the second step, the concentration is lowered.
The pH of the polishing liquid in the substrate polishing method in the present invention is preferably 3 or less.
The polishing liquid for the substrate polishing method in the present invention may further contain a water-soluble polymer.
The water-soluble polymer is preferably at least one selected from the group consisting of polyacrylic acid or a salt thereof, polymethacrylic acid or a salt thereof, polyacrylamide, polyvinyl alcohol, polyamic acid and a salt thereof, and polyvinylpyrrolidone.
When the polishing liquid of the substrate polishing method contains a water-soluble polymer, the oxidizing agent concentration of the polishing liquid used in the second step is preferably 0.01 to 1.5% by weight.
The acid is preferably an organic acid, and is preferably at least one selected from malonic acid, malic acid, tartaric acid, glycolic acid and citric acid.
The protective film forming agent is preferably at least one (BTAs) selected from benzotriazole (BTA) and derivatives thereof that have been widely used.
The conductor oxidizing agent is preferably at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water.
The polishing liquid may contain abrasive grains. The abrasive is preferably at least one selected from silica, alumina, ceria, titania, zirconia, and germania, and is preferably colloidal silica or colloidal alumina having an average particle size of 100 nm or less.
The conductor is copper or a copper alloy and its barrier layer, and the barrier layer is tantalum, tantalum nitride, tantalum alloy, or other tantalum compounds.
The substrate polishing method of the present invention is preferably a polishing method for polishing a surface including copper or a copper alloy and its barrier layer.
The substrate polishing method of the present invention comprises a polishing step in which a polishing rate ratio (Cu / Ta, Cu / TaN) of copper or a copper alloy, tantalum, and tantalum nitride is greater than 20; The polishing rate ratio of copper or copper alloy (Ta / Cu, TaN / Cu) is greater than 1, and the polishing rate ratio of tantalum, tantalum nitride and silicon dioxide film (Ta / SiO ₂ , TaN / SiO ₂ ) is 10 This is a polishing method in which the second step is polished with a large polishing liquid.
In the present invention, the polishing of the copper or copper alloy film, which is the first step, and the polishing of the barrier layer, which is the second step, can be performed efficiently and continuously with only one polishing surface plate by changing the oxidant concentration. Provided is a method for polishing a substrate, which can be carried out and can form a highly reliable embedded pattern of a metal film.
As a method for polishing copper or a copper alloy and a barrier layer below the copper or copper alloy, a method of two-step polishing using another polishing liquid in which the composition of the polishing liquid is changed has been performed. In order to increase time efficiency, it is necessary to prepare a plurality of polishing apparatuses for each of the first process and the second process, or a polishing apparatus having a plurality of surface plates. There was a problem that it was not efficient and economical.
The present inventors have found that polishing of tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds used as a barrier layer easily proceeds in a low oxidant concentration region. The present inventors have found a method in which polishing of copper or copper alloy and subsequent polishing of the barrier layer can be performed with the same component polishing liquid.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a metal film containing a barrier layer and copper or copper alloy is formed and filled on a substrate having a silicon dioxide recess on the surface. When this substrate is first CMPed using a polishing solution for copper and copper alloy having a sufficiently high polishing rate ratio of copper or copper alloy / barrier layer, the barrier layer on the convex portion of the substrate is exposed on the surface, and the copper or copper in the concave portion is exposed. A desired conductor pattern in which the alloy film remains is obtained. The polishing method of the present invention includes a first step of polishing and planarizing copper or a copper alloy using a polishing liquid containing an oxidizing agent for a conductor, a protective film forming agent for a metal surface, an acid and water, and A polishing method comprising a second step of polishing the lower barrier layer of copper or copper alloy, which changes only the concentration of the oxidizing agent in the first step and the second step, is used. If necessary, a polishing liquid to which a water-soluble polymer or abrasive grains are added may be used.
[0013]
The oxidizing agent concentration of the polishing liquid of the substrate polishing method is adjusted to 1.5 to 10% by weight in the first step and 0.01 to 3% by weight in the second step. If the concentration of the oxidizing agent in the first step is less than 1.5% by weight, the polishing rate of copper or copper alloy decreases, and even if it exceeds 10% by weight, the polishing rate of copper or copper alloy does not change. So it's not economical. The polishing rate of tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds is maximized when the concentration of the oxidizing agent in the second step is around 0.15% by weight. A primary oxide layer that is easily mechanically polished is formed on the surface of the conductor film such as tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds by the oxidizing agent, and a high polishing rate can be obtained. If the concentration of the oxidizer exceeds 3% by weight, the etching rate of copper or copper alloy increases, and not only does dishing easily occur, but also conductors such as tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds. Since a secondary oxide layer that is harder to polish than the primary oxide layer is formed on the film surface, the polishing rate decreases. When the concentration of the oxidizing agent is less than 0.01% by weight, the polishing rate becomes low because the oxide layer is not sufficiently formed.
[0014]
In the substrate polishing method of the present invention, the pH of the polishing liquid is preferably adjusted to 3 or less. If the pH of the polishing liquid exceeds 3, the polishing rate of the copper or copper alloy in the first step decreases, and the polishing rate of tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds in the second step decreases. The pH can be adjusted by the amount of acid added. It can also be adjusted by adding alkali components such as ammonia, sodium hydroxide, tetramethylammonium hydride.
[0015]
The polishing liquid in the substrate polishing method of the present invention may contain a water-soluble polymer. In the first step, the water-soluble polymer is adsorbed on copper or copper alloy tantalum, tantalum alloy, tantalum nitride or other tantalum compound, or its oxide film surface, so that an oxidizing agent concentration that provides a high polishing rate is obtained. The range becomes smaller. In addition, since the water-soluble polymer is easily adsorbed on the surface of a nitride compound film such as a tantalum nitride film or titanium nitride, the polishing rate of the nitride compound film such as a tantalum nitride film or titanium nitride is reduced. On the other hand, the water-soluble polymer has the effect of forming a metal surface protective film, and the synergistic effect with the protective film forming agent and the effect of forming the protective film on the substrate surface of the water-soluble polymer make flattening such as dishing and thinning. Improve properties.
[0016]
Examples of the oxidizing agent for the conductor of the polishing liquid in the substrate polishing method include hydrogen peroxide (H ₂ O ₂ ), nitric acid, potassium periodate, hypochlorous acid, and ozone water. Particularly preferred. When the substrate is a silicon substrate including an integrated circuit element, contamination by alkali metal, alkaline earth metal, halide, or the like is not desirable, and thus an oxidizing agent that does not include a nonvolatile component is desirable. However, hydrogen peroxide is most suitable because ozone water has a severe compositional change over time. However, in the case where the substrate to be applied is a glass substrate that does not include a semiconductor element, an oxidizing agent that includes a nonvolatile component may be used.
[0017]
As the acid of the polishing liquid, formic acid, acetic acid, propionic acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalate Acids, malic acid, tartaric acid, citric acid, etc., and salts such as ammonium salts of these organic acids, sulfuric acid, nitric acid, ammonia, ammonium salts such as ammonium persulfate, ammonium nitrate, ammonium chloride, chromic acid, etc., or mixtures thereof Can be mentioned. Among these, malonic acid, malic acid, tartaric acid, glycolic acid, and citric acid are preferable in that a practical CMP polishing rate can be obtained.
[0018]
Examples of the protective film forming agent for the polishing liquid include benzotriazole (BTA), BTA derivatives, for example, one in which one hydrogen atom of the benzene ring of BTA is substituted with a methyl group (tolyltriazole) or one substituted with a carboxyl group (benzo Triazole-4-carboxylic acid, methyl, ethyl, propyl, butyl and octyl esters), or naphthotriazole, naphthotriazole derivatives and mixtures containing these.
[0019]
As the water-soluble polymer of the polishing liquid, those selected from the following group are suitable, and polyacrylic acid, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, polymethacrylic acid, polymethacrylic acid ammonium salt, poly Examples thereof include a polymer having a monomer having a carboxyl group such as sodium methacrylate and polyacrylamide as a basic structural unit and a salt thereof and a polymer having a monomer having a vinyl group such as polyvinyl alcohol and polyvinylpyrrolidone as a basic structural unit. However, when the substrate to be applied is a silicon substrate for a semiconductor integrated circuit or the like, contamination with an alkali metal, an alkaline earth metal, a halide, or the like is not desirable, so an acid or an ammonium salt thereof is desirable. This is not the case when the substrate is a glass substrate or the like. By adding these water-soluble polymers, the dishing characteristics can be improved due to the effect of inhibiting etching by the protective film forming agent.
[0020]
Abrasive grains may be added to the substrate polishing method of the present invention. As the abrasive grains, any of inorganic abrasive grains such as silica, alumina, ceria, titania, zirconia, germania, silicon carbide, and organic abrasive grains such as polystyrene, polyacryl, polyvinyl chloride, etc. may be dispersed in the polishing liquid. Colloidal silica and colloidal alumina having good stability and a small number of polishing scratches (scratches) generated by CMP and having an average particle size of 100 nm or less are preferable. The average particle size is more preferably 20 nm or less, in which the polishing rate of the barrier layer becomes larger and the polishing rate of silicon dioxide becomes smaller. Colloidal silica is known for its production by hydrolysis of silicon alkoxide or ion exchange of sodium silicate, and colloidal alumina is known for its production by hydrolysis of aluminum nitrate.
[0021]
As a conductor film to which the present invention is applied, the first step is copper or a copper alloy, the second step is a barrier layer of copper or copper alloy, and the barrier layer is tantalum, tantalum alloy, tantalum nitride or other It consists of a tantalum compound.
[0022]
In the substrate polishing method of the present invention, the amount of acid in the polishing liquid is 0.0001 to 0.05 mol with respect to 100 g of the total amount of oxidizing agent, acid, protective film forming agent, water-soluble polymer and water. Is preferable, and it is more preferable to set it as 0.001-0.01 mol. When this compounding quantity exceeds 0.05 mol, there exists a tendency for the etching of copper or a copper alloy to increase.
[0023]
The blending amount of the protective film forming agent is preferably 0.0001 to 0.01 mol with respect to 100 g of the total amount of the oxidizing agent, acid, protective film forming agent, water-soluble polymer and water, and is 0.0005 to 0. More preferably, the amount is 0.005 mol. If the amount is less than 0.0001 mol, the etching of copper or copper alloy tends to increase, and the effect remains unchanged even if the amount exceeds 0.01 mol.
[0024]
In the polishing liquid in the substrate polishing method of the present invention, a water-soluble polymer may be added. The blending amount of the water-soluble polymer is preferably 0.001 to 0.5% by weight with respect to 100 g of the total amount of the oxidizing agent, acid, protective film forming agent, water-soluble polymer and water, 0.01 It is more preferable to set it as weight%-0.2 weight%. If the blending amount is less than 0.001% by weight, the combined effect with the protective film forming agent tends not to appear in etching suppression, and if it exceeds 0.5% by weight, the polishing rate by CMP tends to decrease.
[0025]
The polishing liquid in the substrate polishing method of the present invention may contain abrasive grains. The amount of abrasive grains added is preferably 0.01% to 10% by weight and more preferably 0.05% to 5% by weight relative to the total weight. If the blending amount is less than 0.01%, there is no significant difference from the polishing rate when no abrasive grains are contained, and if it exceeds 10% by weight, the polishing rate by CMP is saturated, and no increase is observed even if it is added more than that.
[0026]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not restrict | limited by these Examples.
[0027]
(Examples 1-3)
(Preparation method of polishing liquid)
0.57 parts by weight of acid, 0.07 parts by weight of water-soluble polymer, 0.29 parts by weight of BTA as a protective film forming agent, 99.07 parts by weight of water (99.14 parts by weight when no water-soluble polymer is added) ) Was added to prepare a mixed solution. In the polishing in the first step, the above mixed solution and hydrogen peroxide (special grade reagent, 30% aqueous solution) are mixed at a weight ratio of 7: 3, and in the second step, the mixed solution and hydrogen peroxide (special grade reagent, 30% aqueous solution) is used in a weight ratio of 99.5: 0.5. In the case of adding abrasive grains, 1 part by weight of colloidal silica having an average particle diameter of 20 nm prepared by hydrolysis of tetraethoxysilane in an aqueous ammonia solution is added to the above mixture, and 98.07 parts by weight of water (water-soluble). 98.14 parts by weight when no conducting polymer was added.
In Examples 1 to 3, CMP was performed with the above polishing liquid using the acid and water-soluble polymer described in Table 1.
(Polishing conditions)
Base material: Silicon substrate on which a tantalum film with a thickness of 200 nm is formed Silicon substrate on which a silicon dioxide film with a thickness of 1 μm is formed Silicon substrate polishing pad with a copper film with a thickness of 1 μm: Polyurethane resin polishing pressure with closed cells : 250 gf / cm ²
Relative speed between substrate and polishing surface plate: 18 m / min
(Abrasive product evaluation items)
Polishing rate by CMP: The film thickness difference before and after CMP of the film was calculated from the electric resistance value.
Etching rate: The difference in copper film thickness before and after immersion in a stirred polishing liquid (room temperature, 25 ° C., stirring 100 rpm) was calculated from the electrical resistance value.
Dishing amount: A groove having a depth of 0.5 μm is formed in silicon dioxide, a tantalum nitride film having a thickness of 50 nm is formed as a barrier layer by a known sputtering method, and a copper film is similarly formed by sputtering. Two-step polishing is performed using a silicon substrate embedded by heat treatment as a substrate, and insulation is obtained from the surface shape of the stripe pattern portion in which the wiring metal portion width of 100 μm and the insulating film portion width of 100 μm are alternately arranged by a stylus type step gauge. The amount of reduction of the wiring metal part relative to the film part was determined. Polishing was performed with the polishing liquid in the first step until the barrier layer was exposed in the insulating film portion, and polishing was performed with the polishing liquid in the second step until there was no barrier layer in the insulating film portion. The condition was evaluated.
Thinning amount: Measure the surface shape of the striped pattern part with a total width of 2.5 mm in which the wiring metal part width of 45 μm and the insulating film part width of 5 μm are alternately formed on the above-mentioned substrate for evaluating the dishing amount with a stylus type step gauge Then, the amount of film reduction of the insulating film portion near the center of the pattern with respect to the insulating film field portion around the stripe pattern was obtained. Evaluation was performed after the first step and after the second step.
Table 1 shows the measurement results of the polishing rate and the etching rate by CMP in Examples 1 to 3. Table 2 shows the measurement results of the amount of dishing and the amount of thinning.
[0028]
[Table 1]

[0029]
[Table 2]

[0030]
Example 1 is an example in which abrasive grains and a water-soluble polymer are not blended. In the first step, polishing is performed with a polishing liquid containing a hydrogen peroxide concentration of 9% by weight in the first step, and in the second step, peroxide is used. In this example, polishing is performed with a polishing liquid containing 0.15% by weight of hydrogen. When the hydrogen peroxide concentration in the polishing liquid used in the first step is increased, the polishing rate of copper is 210 nm / min, which is significantly faster than that of 0.3 nm / min of tantalum which is a barrier. On the other hand, if the hydrogen peroxide in the polishing liquid used in the second step is 0.15% by weight, the copper polishing rate is 17.0 nm / min, the barrier tantalum is 4.5 nm / min, and the copper polishing rate. And the polishing rate of tantalum is increased. The polishing rate of silicon dioxide, which is an insulating layer, is very small. The tendency of the polishing rate of copper and barrier tantalum does not change in Example 2 in which abrasive grains are blended and in Example 3 in which water-soluble polymers are blended. When a trench is formed in an insulating layer of silicon dioxide, tantalum is used as a barrier layer to prevent copper diffusion, and a copper layer is provided on the surface, the concentration of hydrogen peroxide as an oxidizing agent is set in the first step. When the increased polishing liquid is used, the polishing rate of the copper layer is high and can be polished in a short time, and the copper layer is polished and the barrier layer is exposed. Once the barrier layer has been exposed, this time, as a polishing liquid in the second step, the concentration of hydrogen peroxide, which is an oxidizing agent, is reduced and polished, the copper polishing rate decreases and the tantalum polishing rate increases. The barrier layer and the copper layer can be polished to the same extent. In this way, in the first step, a polishing solution having a high hydrogen peroxide concentration as an oxidizing agent is supplied by a pump or the like, and when the barrier layer is exposed, a polishing solution having a low hydrogen peroxide concentration is used as the second step. It is good to supply and polish with a pump. The polishing rate of silicon dioxide, which is an insulating layer, is lower than that of copper or tantalum, and polishing can be reliably stopped near the upper surface of this layer.
[0031]
【The invention's effect】
In the substrate polishing method of the present invention, the pH of the polishing liquid is less than 3, and the concentration of the oxidizing agent is 1.5 to 10% by weight in the polishing of copper or copper alloy in the first step, and the barrier in the second step. In the polishing of the layer, by adjusting the concentration to 0.01 to 3% by weight, the polishing of the copper or copper alloy film and the polishing of the barrier layer can be efficiently performed continuously with only one polishing surface plate by changing the oxidant concentration. Therefore, it is possible to form a highly reliable embedded pattern of a metal film.

Claims (12)

A first step of polishing and flattening copper or a copper alloy using a first polishing liquid;
A second step of polishing the lower barrier layer of copper or copper alloy using the second polishing liquid;
A polishing method comprising:
The barrier layer is tantalum, tantalum nitride, tantalum alloy, or other tantalum compound;
Each of the first polishing liquid and the second polishing liquid contains a conductor oxidizing agent, a protective film forming agent for a metal surface, an acid , a water-soluble polymer, and water,
A method for polishing a substrate, wherein the concentration of the oxidant in the second polishing liquid is lower than the concentration of the oxidant in the first polishing liquid.   The oxidant concentration of the first polishing liquid is 1.5 to 10% by weight, and the oxidant concentration of the second polishing liquid is 0.01 to 3% by weight. Substrate polishing method.   The substrate polishing method according to claim 1, wherein the first polishing liquid and the second polishing liquid have a pH of 3 or less. Any said water-soluble polymer, polyacrylic acid or a salt thereof, polymethacrylic acid or salts thereof, polyacrylamides, polyvinyl alcohol, at least one selected from the group consisting of polyvinyl pyrrolidone of claims 1 to 3 the polishing method of substrate according to any. The concentration of the oxidizing agent in the second polishing liquid, the polishing method of substrate according to any one the preceding claims 2 is 0.01 to 1.5 wt% of claim 4. It said acid polishing method of substrate according to any one of claims 1 to 5 is an organic acid. The method for polishing a substrate according to claim 6 , wherein the organic acid is at least one selected from malonic acid, malic acid, tartaric acid, glycolic acid, and citric acid. The protective film forming agent, a polishing method of a substrate according to any one of claims 1 to 7 is at least one selected from benzotriazole (BTA) and its derivatives. It said oxidizing agent is hydrogen peroxide, nitric acid, potassium periodate, a polishing method of a substrate according to any one of claims 1 to 8 is at least one selected from hypochlorous acid and ozone water. Wherein the first polishing liquid and the second polishing solution, the polishing method of substrate according to any one of claims 1 to 9, characterized in that it further added abrasive grains. The method for polishing a substrate according to claim 10 , wherein the abrasive is at least one selected from silica, alumina, ceria, titania, zirconia, and germania. A method for polishing a substrate, wherein a surface including copper or a copper alloy and a barrier layer thereof is polished using the polishing method according to any one of claims 1 to 11 .