JP2002176015A - Polishing liquid for metal and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal polishing liquid capable of forming an embedding pattern of a metal film having high reliability and to provide a method for polishing by using the liquid, by providing a high polishing speed ratio of a base barrier layer to an insulating film layer and by making the plane highly uniform and flat. SOLUTION: The polishing liquid comprises a metal oxidizer, an oxide metal solubilizer, a protective film forming agent, a water soluble polymer and water. The liquid has a polishing speed ratio (metal barrier layer) of the metal to its barrier layer of 10 or more, and a polishing speed ratio of the metal to the insulating film layer (metal/insulating film layer) of 100 or more to be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing liquid for a metal in a wiring step of a semiconductor device and a polishing method using the same.

[0002]

2. Description of the Related Art In recent years, a new fine processing technology has been developed in accordance with high integration and high performance of a semiconductor integrated circuit (LSI). Chemical mechanical polishing (CMP) is one of them.
This is a technique that is frequently used in flattening an interlayer insulating film, forming a metal plug, and forming an embedded wiring in an LSI manufacturing process, particularly in a multilayer wiring forming process. This technique is disclosed, for example, in US Pat. No. 4,944,836.

Recently, use of a copper alloy as a wiring material has been attempted in order to improve the performance of an LSI. However, it is difficult to finely process a copper alloy by a dry etching method frequently used in forming a conventional aluminum alloy wiring. Therefore, a copper alloy thin film is deposited and buried on an insulating film in which a groove is formed in advance, and a copper alloy thin film other than the groove is removed by CMP to form a buried wiring.
The so-called damascene method is mainly employed. This technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-278822.

A general method of metal CMP is to attach a polishing cloth (pad) on a circular polishing platen (platen),
The surface of the polishing cloth is immersed in a polishing liquid for metal, the surface of the substrate on which the metal film is formed is pressed, and the polishing platen is rotated while applying a predetermined pressure (polishing pressure or polishing load) from the back surface thereof. The metal film on the convex portion is removed by mechanical friction with the convex portion of the metal film.

[0005] The metal polishing liquid used for CMP generally comprises an oxidizing agent and solid abrasive grains, and if necessary, a metal oxide dissolving agent and a protective film forming agent are further added. It is considered that the basic mechanism is to first oxidize the surface of the metal film by oxidation and to scrape off the oxidized layer with solid abrasive grains. The oxide layer on the metal surface of the concave portion does not substantially touch the polishing pad, and the effect of the shaving by the solid abrasive grains does not reach. Therefore, as the CMP proceeds, the metal layer on the convex portion is removed and the substrate surface is flattened. See the Journal of Electrochemical Society (Journal of
Vol. 138, No. 11 (19)
1991), pages 3460-3364.

As a method of increasing the polishing rate by CMP, it is effective to add a metal oxide dissolving agent. It can be interpreted that dissolving the metal oxide particles removed by the solid abrasive grains in the polishing liquid increases the effect of the solid abrasive grains. However, when the oxidized layer on the surface of the metal film in the recess is also dissolved (etched) to expose the surface of the metal film, the oxidizing agent further oxidizes the surface of the metal film, and if this is repeated, the etching of the metal film in the recess proceeds. It is feared that the flattening effect is impaired.
In order to prevent this, a protective film forming agent is further added. It is important to balance the effects of the metal oxide dissolving agent and the protective film forming agent. The oxide layer on the surface of the metal film in the concave portion is not etched so much, the particles of the cut oxide layer are efficiently dissolved, and polishing by CMP is performed. High speed is desirable.

As described above, by adding the metal oxide dissolving agent and the protective film forming agent to add the effect of the chemical reaction, the CMP
The speed (polishing speed by CMP) is improved and the CM
The effect of reducing the damage (damage) on the surface of the metal layer to be P is obtained.

However, when a buried wiring is formed by CMP using a conventional metal polishing slurry containing solid abrasive grains, (1) the surface central portion of the buried metal wiring is isotropically corroded. The phenomenon of dishing (dishing), the phenomenon in which the insulating film is polished in a portion where the wiring density is high and the thickness of the metal wiring becomes thin (erosion or thinning), and (2) originating from solid abrasive grains Generation of polishing scratches (3) Complicated cleaning process for removing solid abrasive particles remaining on the substrate surface after polishing, (4) Cost of solid abrasive particles themselves and waste liquid treatment Problems such as cost increase occur.

In order to suppress the corrosion of the copper alloy during dishing and polishing and to form a highly reliable LSI wiring, a metal oxide dissolving agent composed of aminoacetic acid or amide sulfuric acid such as glycine and BTA (benzotriazole) are used. A method using a contained metal polishing liquid has been proposed. This technique is described in, for example, Japanese Patent Application Laid-Open No. 8-83780.

In the formation of a metal buried such as the formation of a damascene wiring of copper or a copper alloy or the formation of a plug wiring of tungsten or the like, when the polishing rate of a silicon dioxide film which is an interlayer insulating film formed in a portion other than the buried portion is high, Erosion occurs in which the thickness of the wiring together with the interlayer insulating film is reduced. As a result, variations in resistance occur due to an increase in wiring resistance, pattern density, and the like. Therefore, a characteristic in which the polishing rate of the silicon dioxide film is sufficiently low relative to the metal film to be polished is required. Therefore, a method has been proposed in which the polishing rate of the polishing liquid is made higher than pKa-0.5 by suppressing the polishing rate of silicon dioxide by anions generated by dissociation of the acid. This technology is disclosed, for example, in Japanese Patent No. 2891919.
No. 6 is described.

On the other hand, a tantalum, a tantalum alloy, a tantalum nitride, another tantalum compound, or the like is formed as a barrier layer for preventing copper from diffusing into an interlayer insulating film in a lower layer of a wiring such as copper or a copper alloy. . Therefore, it is necessary to remove the exposed barrier layer by CMP except for the wiring portion where 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 often cannot provide a sufficient CMP rate. If the barrier layer is continuously polished with such a polishing liquid, dishing of the copper or copper alloy portion occurs. Therefore, a two-step polishing method including a first step of polishing copper or a copper alloy and a second step of polishing the barrier layer conductor has been studied.

In a two-step polishing method comprising a first step of polishing copper or a copper alloy and a second step of polishing a barrier layer,
The hardness and chemical properties of the film to be polished are different, and the polishing rate of copper or copper alloy needs to be changed.
Compositions such as H, abrasive grains and additives that have significantly different properties are being investigated.

[0013]

In order to form a buried wiring having good electrical characteristics with less dishing and erosion, it is necessary to make the polishing rate of a metal such as a copper alloy sufficiently higher than the etching rate. for that reason,
Although a polishing liquid having a large mechanical polishing action containing solid abrasive grains is used, in a polishing liquid having a large mechanical polishing action,
Not only the wiring metal but also the barrier layer and the insulating film thereunder are polished. As a result, there is a problem that dishing and erosion occur and the wiring resistance value increases.
When a polishing liquid having such characteristics is used, single-step polishing in which the metal and the barrier layer are continuously polished with one polishing liquid is also possible, but a surface which only suppresses variation in wiring resistance to within an allowable range is possible. It is very difficult to achieve internal uniformity.
The first-stage polishing liquid for the second-stage polishing includes a polishing rate ratio between a metal layer such as a copper alloy and a barrier layer (metal / barrier layer) and a polishing rate ratio between a metal layer and an insulating film layer (metal / insulating film layer). ) Is sufficiently large so that polishing is stopped at the barrier layer or the insulating film layer thereunder, and a metal polishing liquid having a sufficiently high CMP rate with respect to the etching rate of a metal layer such as a copper alloy is desired. Was rare. The present invention expresses a high polishing rate ratio between the underlying barrier layer and the insulating film layer, enables high in-plane uniformity and high flatness, and enables formation of a highly reliable buried pattern of a metal film. And a polishing method using the same.

[0014]

The polishing solution for metals of the present invention is a polishing solution containing a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, a water-soluble polymer and water. The polishing rate ratio of the layer (metal / barrier layer) is 10 or more, and the polishing rate ratio of the metal and the insulating film layer (metal / insulating film layer) is 100 or more. The water-soluble polymer used in the present invention is preferably at least one selected from those having a weight average molecular weight of 500 or more. The water-soluble polymer used in the present invention is preferably at least one selected from polysaccharides, polycarboxylic acids, polycarboxylic esters and salts thereof, and vinyl polymers. The metal oxidizing agent used in the present invention is preferably at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid and ozone water. The metal oxide dissolving agent used in the present invention is preferably at least one selected from organic acids, organic acid esters, ammonium salts of organic acids, and sulfuric acid. The protective film forming agent used in the present invention forms a protective film on a metal surface, and the protective film forming agent is at least one selected from nitrogen-containing compounds and salts thereof, mercaptan, glucose and cellulose. One is preferred. At least a metal film is formed by a step of polishing a metal film comprising a laminated film including at least one metal layer selected from copper, a copper alloy, and an oxide thereof (hereinafter, referred to as a copper alloy) using the metal polishing slurry of the present invention. Can be partially removed. Using the metal polishing slurry of the present invention, at least a metal film is formed by a step of polishing a metal film composed of a laminated film including at least one metal barrier layer selected from tantalum, tantalum nitride, a tantalum alloy, and other tantalum compounds. Can be partially removed. The polishing liquid for metal of the present invention has a polishing rate ratio (Cu / Ta) of copper (including copper alloy) to tantalum of 50 or more, and a polishing rate ratio of copper (including copper alloy) to a silicon dioxide film (Cu). / SiO ₂ ) is preferably 100 or more. The polishing liquid for metal of the present invention has a polishing rate ratio (Cu / Ta) of copper (including copper alloy) to tantalum of 1000 or more, and a polishing rate ratio of copper (including copper alloy) to a silicon dioxide film (Cu). / SiO ₂ ) is preferably 1000 or more. The polishing liquid for metal of the present invention has a polishing rate ratio (Cu / TaN) of copper (including copper alloy) to tantalum nitride of 50 or more, and a polishing rate ratio of copper (including copper alloy) to a silicon dioxide film ( (Cu / SiO ₂ ) is preferably 100 or more. The polishing liquid for metal of the present invention has a polishing rate ratio (Cu / TaN) of copper (including copper alloy) to tantalum nitride of 1000 or more, and a polishing rate ratio of copper (including copper alloy) to silicon dioxide film ( (Cu / SiO ₂ ) is preferably 1000 or more. The polishing slurry for metals of the present invention preferably has a polishing flaw of 0.2 μm or more on the surface of copper (including a copper alloy) after polishing is 1 piece / cm ² or less. The polishing method of the present invention,
Polishing the film to be polished by moving the polishing platen and the substrate relatively while the substrate having the film to be polished is pressed against the polishing cloth while supplying the metal polishing liquid on the polishing cloth of the polishing platen. can do.

In the present invention, a high polishing rate ratio (metal / barrier layer) between a metal layer such as a copper alloy and a barrier layer (metal / barrier layer) and a high polishing rate between a metal layer and an insulating film layer are obtained by combining a protective film forming agent and a water-soluble polymer. It is possible to provide a metal polishing liquid having a rate ratio (metal / insulating film layer) characteristic and exhibiting an effect that a CMP rate is sufficiently large with respect to an etching rate. As the protective film forming agent, one that easily forms a chelate complex with copper, for example, ethylenediaminetetraacetic acid, benzotriazole, or the like is used. These metal surface protective film forming effects are extremely strong,
For example, if the metal polishing slurry contains 0.5% by weight or more, the copper alloy film is not etched, not even CMPed.

On the other hand, the present inventors, by using a protective film forming agent and a water-soluble polymer in combination, have a high CM while maintaining a sufficiently low etching rate of a metal layer such as a copper alloy.
It has been found that a P speed can be obtained. Moreover, it has been found that the use of such a polishing liquid enables polishing at a practical CMP rate without including a solid abrasive in the polishing liquid. This is considered to be due to the fact that the scraping due to the friction of the polishing pad was developed in contrast to the conventional effect of scraping due to the friction of the solid abrasive grains. However, since the polishing of the barrier layer and the insulating film layer hardly proceeds by friction with the polishing cloth, a high polishing rate ratio between the metal layer and the barrier layer and between the metal layer and the insulating film layer can be obtained.

The polishing rate ratio between metal and its barrier layer (metal / metal)
If the barrier layer is 10 or more, the barrier layer acts as a stopper, so that the polishing of the first-layer metal layer such as a copper alloy is finished in a state where the barrier layer thickness is uniform, and the second-layer barrier layer You can proceed to polishing. More preferably, the polishing rate ratio (metal / barrier layer) between the metal and its barrier layer is 1000 or more. Further, if the polishing rate ratio between the metal and the insulating film layer (metal / insulating film layer) is 100 or more, even if the barrier layer on the insulating film is removed by erosion at a portion where the metal wiring density is high or the like, the insulation will not occur. The film layer serves as a stopper, which can prevent a decrease in the wiring thickness due to the progress of erosion. More preferably, the polishing rate ratio between the metal and the insulating film layer (metal / insulating film layer) is 1000 or more. It has been found that a preferable flattening effect can be obtained if the value of the etching rate can be suppressed to 10 nm / min or less. If the decrease in the CMP rate is within an acceptable range, it is desirable that the etching rate be further lower. If the etch rate can be suppressed to 5 nm / min or less, for example, about 50% of excess CMP (1.5 times the time required for removing the metal film by CMP) Dishing) does not cause any problem. Further, if the etching rate can be suppressed to 1 nm / min or less, dishing does not pose a problem even if excess CMP of 100% or more is performed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a metal film containing copper and a copper alloy (such as copper / chromium) is formed and filled on a substrate having a concave portion on the surface. When the substrate is subjected to CMP using the polishing slurry for metal according to the present invention, the metal film on the convex portion of the substrate is selectively CMPed, and the metal film is left in the concave portion to obtain a desired conductor pattern. In the metal polishing slurry of the present invention, substantially no solid abrasive grains may be contained, and the friction with a polishing pad which is much more mechanically softer than the solid abrasive grains may cause the CM.
In order for P to advance, the polishing rate ratio (metal / barrier layer) of the metal and its barrier layer (metal / barrier layer) is 10 or more, and the metal and the insulating film layer (metal / barrier layer)
A high polishing rate ratio of 100 or more for the insulating film layer) is obtained, and polishing scratches are dramatically reduced. The metal polishing slurry of the present invention contains a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, a water-soluble polymer and water as essential components. Solid abrasive grains need not be substantially contained.

[0019] as an oxidizing agent of the metal, hydrogen peroxide (H ₂
O ₂ ), nitric acid, potassium periodate, hypochlorous acid, ozone water, etc., of which hydrogen peroxide is particularly preferred. When the base is a silicon substrate including an element for an integrated circuit, contamination by an alkali metal, an alkaline earth metal, a halide, or the like is not desirable. Therefore, an oxidizing agent containing no nonvolatile component is desirable. However, hydrogen peroxide is most suitable because the composition of ozone water changes drastically with time. However, when the substrate to be applied is a glass substrate or the like that does not contain a semiconductor element, an oxidizing agent containing a nonvolatile component may be used.

The metal oxide dissolving agent is preferably water-soluble. Aqueous solutions of those selected from the following groups are suitable.
Formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid,
-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, phthalic acid, malic acid, tartaric acid, citric acid, etc., and salts of these organic acids such as ammonium salt, sulfuric acid, nitric acid, ammonia, ammonium salts such as ammonium persulfate, ammonium nitrate, ammonium chloride And chromic acid and the like, and mixtures thereof. Among these, formic acid, malonic acid, malic acid, tartaric acid, and citric acid are suitable for a laminated film including at least one metal layer selected from copper, a copper alloy, and an oxide of copper or a copper alloy. These are preferred in that they can be easily balanced with the first and second protective film forming agents described later. In particular, malic acid, tartaric acid, and citric acid are preferable in that the etching rate can be effectively suppressed while maintaining a practical CMP rate.

The protective film forming agent is preferably selected from the following group. Ammonia; alkylamines such as dimethylamine, trimethylamine, triethylamine and propylenediamine, and ethylenediaminetetraacetic acid (E
DTA), sodium diethyldithiocarbamate and amines such as chitosan; glycine, L-alanine, β-alanine, L-2-aminobutyric acid, L-norvaline, L-valine, L-leucine, L-norleucine, L-isoleucine; L-alloisoleucine, L-phenylalanine,
L-proline, sarcosine, L-ornithine, L-lysine, taurine, L-serine, L-threonine, L-allothreonine, L-homoserine, L-tyrosine, 3,5-
Diodo-L-tyrosine, β- (3,4-dihydroxyphenyl) -L-alanine, L-thyroxine, 4-hydroxy-L-proline, L-cystine, L-methionine, L-ethionine, L-lanthionine , L-cystathionine, L-cystine, L-cystinic acid, L-aspartic acid, L-glutamic acid, S- (carboxymethyl) -L-cystine, 4-aminobutyric acid, L-asparagine, L-glutamine, azaserine, L -Arginine,
L-canavanine, L-citrulline, δ-hydroxy-L
-Lysine, creatine, L-kynurenine, L-histidine, 1-methyl-L-histidine, 3-methyl-L-histidine, ergothioneine, L-tryptophan, actinomycin C1, apamin, angiotensin I,
Amino acids such as angiotensin II and antipain;
Dithizone, cuproin (2,2′-biquinoline), neocuproin (2,9-dimethyl-1,10-phenanthroline), bathocuproine (2,9-dimethyl-4,7)
Imines such as -diphenyl-1,10-phenanthroline) and cuperazone (biscyclohexanone oxalyl hydrazone); benzimidazole-2-thiol;
2- [2- (benzothiazolyl)] thiopropionic acid,
2- [2- (benzothiazolyl) thiobutyric acid, 2-mercaptobenzothiazole, 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-
1,2,4-triazole, benzotriazole, 1-
Hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4-carboxyl-1H-benzotriazole,
4-methoxycarbonyl-1H-benzotriazole,
4-butoxycarbonyl-1H-benzotriazole,
4-octyloxycarbonyl-1H-benzotriazole, 5-hexylbenzotriazole, N- (1,
2,3-benzotriazolyl-1-methyl) -N-
Azole such as (1,2,4-triazolyl-1-methyl) -2-ethylhexylamine, tolyltriazole, naphthotriazole, bis [(1-benzotriazolyl) methyl] phosphonic acid; nonylmercaptan, dodecylmercaptan, triazine Mercaptans such as thiol, triazinedithiol and triazinetrithiol; and saccharides such as glucose and cellulose. Among them, chitosan, ethylenediaminetetraacetic acid, L-tryptophan, cuperazone, triazinedithiol, benzotriazole, 4-hydroxybenzotriazole, 4-carboxylbenzotriazole butyl ester, tolyltriazole, and naphthotriazole have high C.
It is preferable to achieve both the MP rate and the low etching rate.

As the water-soluble polymer, those selected from the following group are preferred. Polysaccharides such as alginic acid, pectic acid, carboxymethyl cellulose, agar, cardran and pullulan; amino acid salts such as glycine ammonium salt and glycine sodium salt; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid , Polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyamic acid, polymaleic acid,
Polyitaconic acid, polyfumaric acid, poly (p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, ammonium polyacrylate, sodium polyacrylate, polyamic acid, ammonium polyamic acid, sodium polyamic acid And polycarboxylic acids such as polyglyoxylic acid and esters and salts thereof; and vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein. However, when the substrate to be applied is a silicon substrate for a semiconductor integrated circuit or the like, an acid or an ammonium salt thereof is preferable because contamination by an alkali metal, an alkaline earth metal, a halide or the like is not desirable. This is not the case when the substrate is a glass substrate or the like. Among them, pectic acid, agar, polymalic acid, polymethacrylic acid, ammonium polyacrylate, polyacrylamide, polyvinyl alcohol and polyvinylpyrrolidone, their esters and their ammonium salts are preferred.

The amount of the metal oxidizing agent is 0.003 to 0.7 mol based on 100 g of the total amount of the metal oxidizing agent, metal oxide dissolving agent, protective film forming agent, water-soluble polymer and water.
Is preferably set to 0.03 to 0.5 mol, more preferably 0.2 to 0.3 mol. If the amount is less than 0.003 mol, the metal is not sufficiently oxidized and the CMP rate is low.
If it exceeds mol, the polished surface tends to be rough.

In the present invention, the compounding amounts of the metal oxide dissolving agent component are as follows: metal oxidizing agent, metal oxide dissolving agent, protective film forming agent,
0.000 for 100 g of water-soluble polymer and water
It is preferably from 0.01 to 0.005 mol, and 0.0
It is more preferably from 0005 to 0.0025 mol, particularly preferably from 0.0005 to 0.0015 mol. When the amount exceeds 0.005 mol, it tends to be difficult to suppress the etching.

The compounding amount of the protective film forming agent may be an oxidizing agent for a metal,
The amount is preferably 0.0001 to 0.05 mol, more preferably 0.0003 to 0.005 mol, and more preferably 0.00005 to 100 g of the total amount of the metal oxide dissolving agent, the protective film forming agent, the water-soluble polymer and water. ~ 0.0035
Particularly preferably, it is mol. If the amount is 0.0
If it is less than 001 mol, the suppression of etching tends to be difficult, and if it exceeds 0.05 mol, the CMP rate tends to be low.

The compounding amount of the water-soluble polymer depends on the oxidizing agent for the metal,
It is preferably 0.001 to 0.3% by weight, more preferably 0.003 to 0.1% by weight, based on 100 g of the total amount of the metal oxide dissolving agent, the protective film forming agent, the water-soluble polymer and the water. It is particularly preferred that the content be 0.01 to 0.08% by weight. If the amount is less than 0.001% by weight,
There is a tendency that the effect of the combined use with the protective film forming agent does not appear in the suppression of etching, and when it exceeds 0.3% by weight, the CMP rate tends to decrease. The weight average molecular weight of the water-soluble polymer is preferably 500 or more, more preferably 1500 or more, and particularly preferably 5000 or more. The upper limit of the weight average molecular weight is not particularly limited, but is 5,000,000 or less from the viewpoint of solubility. If the weight average molecular weight is less than 500, a high CMP rate tends not to be exhibited. In the present invention, the weight average molecular weight is 500
It is preferable to use at least one or more water-soluble polymers described above.

The metal film to which the present invention is applied is a laminated film containing at least one selected from copper, a copper alloy, and an oxide of copper or a copper alloy.

The metal film to which the present invention is applied is a laminated film including at least one metal barrier layer selected from tantalum, tantalum nitride, a tantalum alloy, and other tantalum compounds.

The polishing slurry for metal of the present invention has a polishing rate ratio (Cu / Ta) of copper (including copper alloy) to tantalum of 50 or more, and a polishing rate of copper (including copper alloy) to silicon dioxide film. Preferably, the ratio (Cu / SiO ₂ ) is 100 or more.

The polishing slurry for metal of the present invention has a polishing rate ratio (Cu / Ta) of copper (including copper alloy) and tantalum (Cu / Ta) of 1000.
It is preferable that the polishing rate ratio (Cu / SiO ₂ ) between copper (including a copper alloy) and a silicon dioxide film be 1000 or more.

The metal polishing slurry of the present invention has a polishing rate ratio (Cu / TaN) of 5% between copper (including copper alloy) and tantalum nitride.
It is preferably 0 or more, and the polishing rate ratio (Cu / SiO ₂ ) between copper (including copper alloy) and the silicon dioxide film is 100 or more.

The metal polishing slurry of the present invention has a polishing rate ratio (Cu / TaN) of 1 between copper (including a copper alloy) and tantalum nitride.
It is preferable that the polishing rate ratio (Cu / SiO ₂ ) of copper (including copper alloy) to the silicon dioxide film (Cu / SiO ₂ ) be 1000 or more.

The metal polishing slurry of the present invention has a polishing scratch of 0.2 μm or more on the surface of copper (including a copper alloy) after polishing is 1 piece / cm ² or less. The polishing flaw is inspected by a wafer appearance inspection apparatus (for example, WI-890 manufactured by Hitachi Tokyo Electronics Co., Ltd.) at a sensitivity at which 0.2 μm latex standard particles on the wafer are detected.

In the polishing method of the present invention, the substrate having the film to be polished is pressed against the polishing cloth while the polishing liquid for metal is supplied onto the polishing cloth of the polishing table. This is a polishing method for polishing a film to be polished by moving it in a horizontal direction. As an apparatus for polishing, a general polishing apparatus having a holder for holding a semiconductor substrate and a platen on which a polishing cloth (pad) is attached (a motor or the like capable of changing the number of rotations is attached) can be used. As the polishing cloth, general nonwoven fabric, foamed polyurethane, porous fluororesin and the like can be used, and there is no particular limitation. The polishing conditions are not limited, but the rotation speed of the platen is preferably low, such as 200 rpm or less so that the substrate does not pop out. The pressing pressure of the semiconductor substrate having the film to be polished against the polishing cloth is 9.8 to 98 KPa (100 KPa).
To 1000 gf / cm ² )
In order to satisfy the uniformity of the P speed within the wafer surface and the flatness of the pattern, it is necessary to use 9.8 to 49 KPa (100 to 500 g).
f / cm ² ). During polishing, a metal polishing liquid is continuously supplied to the polishing cloth by a pump or the like. The supply amount is not limited, but it is preferable that the surface of the polishing pad is always covered with the polishing liquid. After the polishing is completed, the semiconductor substrate is preferably washed well in running water, and then dried by spin-drying or the like to remove water droplets attached to the semiconductor substrate.

According to the present invention, it is possible to flatten a CMP of a metal film such as a copper alloy by friction with a polishing pad without using solid abrasive grains.
It is possible to provide a polishing liquid for metal that has a barrier rate of 10 or more and a high polishing rate ratio of 100 or more between a metal and an insulating film layer (metal / insulating film layer). As a result, in the first-stage polishing of a copper alloy or the like in the two-stage polishing process, the polishing time can be easily controlled and the polishing with excellent in-plane uniformity can be realized by using the barrier layer and the insulating film layer as stoppers. it can. As a result, it is possible to reduce variations in electrical characteristics due to a decrease in wiring thickness due to erosion or the like. In addition, polishing scratches are dramatically reduced because no solid abrasive grains are contained. It is presumed that the use of a protective film-forming agent and a water-soluble polymer in this metal polishing solution suppresses etching but prevents CMP from proceeding without functioning as a metal surface protective film against friction caused by a polishing cloth. . In general, in CMP, the degree of occurrence of polishing scratches depends on the grain size, grain size distribution, and shape of solid abrasive grains. Depending on the grain size and the physical properties of the polishing pad, benzotriazole (BT)
In the case of the treatment A), the dishing of the metal film is considered to depend on the hardness of the polishing pad and the chemical properties of the polishing liquid. That is, hard solid abrasive grains are necessary for the progress of CMP, but are not desirable for improving the flattening effect in CMP and the integrity of the CMP surface (there is no damage such as polishing scratches). It can be seen that the flattening effect actually depends on the characteristics of the polishing pad which is softer than the solid abrasive grains.
From this, in the present invention, even if there is no solid abrasive, CMP
It can be understood that it is extremely desirable for the CMP of the copper alloy and, consequently, the formation of the buried pattern using the same in that the progress of the process is realized.

[0036]

The present invention will be described below in detail with reference to examples. The present invention is not limited by these examples. (Preparation of Polishing Solution for Metal) 0.16 parts by weight of DL-malic acid (special reagent grade) as a metal oxide dissolving agent was dissolved by adding 69.6 parts by weight of water. 2 parts by weight and 0.05 parts by weight of water-soluble polymer (solid content) were added. Finally, 30.0 parts by weight of aqueous hydrogen peroxide (reagent grade, 30% by weight aqueous solution) was added as a metal oxidizing agent, and the resultant was used as a metal polishing liquid. In Comparative Example 3, an abrasive having a particle size of 100
nm of colloidal silica was added (water was added in 6 parts).
8.6 parts by weight). As the colloidal silica, one obtained by perhydrolysis in an aqueous ammonia solution of tetraethoxysilane was used.

In Examples 1 to 5 and Comparative Examples 1 to 3, Table 1
Using the various protective film forming agents described in the above section, CMP was performed under the following polishing conditions using the above-mentioned metal polishing slurry. (Polishing conditions) Substrate: Silicon substrate on which a 200 nm-thick tantalum film was formed Silicon substrate on which a 1 μm-thick silicon dioxide film was formed Silicon substrate having a 1 μm-thick copper film Wiring groove depth 0.5 μm / barrier layer : Tantalum film thickness 50n
Polishing cloth: (IC1000 (Rodel)) Foamed polyurethane resin with closed cells Polishing pressure: 20.6 KPa (210 g / cm ² ) Substrate and polishing platen Relative speed: 36 m / min (evaluation of the polished product) CMP speed: The film thickness difference before and after the CMP of each film was obtained by converting from the electric resistance value. Etching rate: The difference in the thickness of the copper layer before and after immersion in a stirred metal polishing liquid (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 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 a sputtering method to a thickness of 1.0 μm. Polishing was performed using a silicon substrate embedded by a known heat treatment as a base.
As the first-stage polishing of copper, polishing was performed on the entire surface of the substrate until the tantalum barrier layer on silicon dioxide was exposed. Wiring metal part width 100μm, insulation film part width 10
From the surface shape of the stripe pattern portion in which 0 μm was alternately arranged, the amount of film reduction of the wiring metal portion with respect to the insulating film portion was determined. Erosion amount: The surface shape of a stripe pattern portion having a total width of 2.5 mm formed by alternately arranging a wiring metal portion width of 45 μm and an insulating film portion width of 5 μm formed on the dishing amount evaluation substrate is measured by a stylus type profilometer. 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 determined. Wiring resistance: A Ta barrier slurry (Ta / Cu) having a sufficiently high polishing rate ratio as the second polishing after the first polishing of copper.
> 1, Ta / SiO ₂ > 50), and the wiring resistance was measured after removing the Ta barrier layer. A wiring resistance value of a wiring length of 1 mm was measured on a 100 μm-wide copper wiring pattern of a dishing amount measuring unit. In the 4.5 μm-wide copper wiring pattern of the erosion amount measuring unit,
The wiring resistance value of the wiring length of 1 mm was measured. Examples 1 to 5
Table 1 shows polishing rates and polishing rate ratios by CMP in Comparative Examples 1 to 3. Table 2 shows the dishing and erosion characteristics, and Table 3 shows the wiring resistance.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

In Comparative Examples 1 and 2, although the polishing rate ratio of copper is large, the dishing and erosion are large and the wiring resistance is increased because the etching rate of copper is high. In Comparative Example 3, the polishing rate between the tantalum and the silicon dioxide film was high, and the polishing rate ratio (particularly Cu / S
Since iO ₂ ) is small, the thickness of the wiring is reduced by erosion, and the wiring resistance is greatly increased. In contrast, in Examples 1 to 5, the polishing rate ratio between copper and tantalum (Cu / T
Since a) is approximately 1000 or more and the polishing rate ratio (Cu / SiO ₂ ) between the copper and the silicon dioxide film is larger than 1500, the increase in wiring resistance is small due to good dishing and erosion characteristics.

[0042]

The metal polishing slurry of the present invention exhibits a high polishing rate ratio with respect to the underlying barrier layer and the insulating film layer, and provides a highly reliable metal film having good in-plane uniformity and flattening characteristics. A metal polishing liquid capable of forming a buried pattern and a polishing method using the same are provided.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tsuyoshi Uchida 48 Wadai, Tsukuba, Ibaraki Prefecture Within Hitachi Chemical Co., Ltd. (72) Inventor Hiroki Terasaki 48 Wadai, Tsukuba, Ibaraki Hitachi Chemical Co., Ltd. In-house (72) Inventor Akiko Igarashi 48 Wadai, Tsukuba-shi, Ibaraki F-term in Hitachi Chemical Co., Ltd. Research Laboratory 3C058 AA07 AC04 CB01 CB03 DA12 DA17

Claims (14)

[Claims] 1. A polishing liquid containing a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, a water-soluble polymer and water,
A polishing slurry for metals, wherein the polishing rate ratio between metal and its barrier layer (metal / barrier layer) is 10 or more, and the polishing rate ratio between metal and insulating film layer (metal / insulating film layer) is 100 or more. 2. The water-soluble polymer has a weight average molecular weight of 500.
The metal polishing slurry according to claim 1, wherein at least one of the above is used. 3. The metal according to claim 1, wherein the water-soluble polymer is at least one selected from polysaccharides, polycarboxylic acids, polycarboxylic esters and salts thereof, and vinyl polymers. Polishing liquid. 4. The method according to claim 1, wherein the metal oxidizing agent is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid and ozone water. Polishing liquid for metal. 5. The metal polishing slurry according to claim 1, wherein the metal oxide dissolving agent is at least one selected from organic acids, organic acid esters, ammonium salts of organic acids, and sulfuric acid. . 6. The metal polishing slurry according to claim 1, wherein the protective film forming agent is at least one selected from a nitrogen-containing compound and a salt thereof, mercaptan, glucose and cellulose. 7. The metal-polishing liquid according to claim 1, wherein the metal film to be polished contains at least one selected from copper, copper alloys and oxides thereof. 8. The metal polishing liquid according to claim 1, wherein the metal barrier layer to be polished is tantalum, tantalum nitride, a tantalum alloy, or another tantalum compound. 9. A polishing rate ratio (Cu / Ta) of copper, copper alloy and their oxides, and tantalum is 50 or more,
Copper, copper alloys and their oxides, a metal-polishing liquid according to claim 1 polishing rate ratio of the silicon dioxide film (Cu / SiO ₂₎ of 100 or more. 10. A polishing rate ratio (Cu / Ta) of copper, a copper alloy and their oxides to tantalum is 1000 or more, and a polishing rate ratio of copper, a copper alloy and their oxides and a silicon dioxide film. (Cu / SiO ₂₎ the metal polishing slurry of claim 1 is 1000 or more. 11. A polishing rate ratio (Cu / TaN) of copper, a copper alloy and their oxides to tantalum nitride is 50 or more, and a polishing rate of copper, a copper alloy and their oxides and a silicon dioxide film. the ratio (Cu / SiO ₂₎ is a metal-polishing liquid according to claim 1 is 100 or more. 12. A polishing rate ratio (Cu / TaN) of copper, a copper alloy, an oxide thereof, and tantalum nitride is 1000 or more, and a polishing rate of a copper, a copper alloy, an oxide thereof, and a silicon dioxide film. the metal polishing slurry according to claim 1 ratio (Cu / SiO ₂₎ is 1,000 or more. 13. Polishing scratches of 0.2 μm or more on the surface of copper, copper alloy and their oxides after polishing are 1 piece / cm.
13. The metal polishing liquid according to claim 1, which is ² or less. 14. A polishing method in which a substrate having a film to be polished is pressed against a polishing cloth while the polishing liquid for a metal according to claim 1 is supplied onto a polishing cloth of a polishing platen. A polishing method for polishing a film to be polished by relatively moving a surface plate and a substrate.