JP2002206086A - Polishing liquid for metal and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid which is used for metals, can reduce the quantity of erosion in a metal wiring portion having a high wiring density in comparison with that by conventional technology, and can form a metal film-buried pattern having high reliability, and to provided a polishing method using the same. SOLUTION: This polishing liquid which contains a metal oxide, a metal oxide-dissolving agent, a protecting film-forming agent, a water-soluble polymer and water, and in which the dented quantity (erosion quantity) of an insulated film portion from a peripheral insulated film layer is <=80 nm, when a metal film formed for bury in a wiring portion is removed on the insulated film on the periphery of a pattern in the pattern in which 4.5 μm wide metal-buried wirings and 0.5 μm-wide insulating films are alternately formed or the pattern in which 1 to 10 μm metal-buried wirings and 0.1 to 1 μm insulated films are alternately formed and which has a wiring pattern density of >=70%, is 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 solution for metal, the surface of the substrate on which the metal film is formed is pressed, and the polishing platen is rotated with a predetermined pressure (polishing pressure or polishing load) applied from the back surface. 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 touch the polishing cloth very much, and the effect of the shaving by the solid abrasive grains does not reach.
As the MP progresses, the metal layer of the convex portion is removed, and the substrate surface is flattened. See the Journal of Electrochemical Society for more information.
Rochemical Society, Vol. 138, No. 11, published in 1991, pp. 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,
In a portion having a high wiring density, polishing of a narrow pattern convex portion progresses along with polishing of a wiring metal film, and eventually erosion occurs. Further, in order to remove the metal film other than the wiring portion on the entire surface of the substrate to be polished, it is necessary to set the polishing time in accordance with the portion having the lowest polishing rate.
Therefore, overpolishing is performed on a portion where polishing has progressed first, but there has been a problem that erosion is significantly increased in the overpolished portion. There has been a demand for a metal polishing liquid having a characteristic that the amount of erosion in a metal wiring portion having a high wiring density is smaller than that of the conventional technology, and the amount of increase in erosion when over-polishing is smaller than that of the conventional technology. An object of the present invention is to provide a metal polishing liquid which enables the amount of erosion in a metal wiring portion having a high wiring density to be smaller than that of the prior art, and enables a highly reliable buried pattern of a metal film to be formed. An object of the present invention is to provide a polishing method used.

[0014]

The polishing liquid for metals of the present invention is a polishing liquid containing a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, a water-soluble polymer and water, and has a width of 4.5 μm.
m, a pattern in which metal embedded wiring and an insulating film having a width of 0.5 μm are alternately formed, or a wiring pattern density of alternately forming a metal embedded wiring having a width of 1 to 10 μm and an insulating film having a width of 0.1 to 1 μm is 70%. In the above pattern, the amount of dent (erosion amount) from the peripheral insulating film layer in the insulating film portion when the metal film formed for embedding in the wiring portion is polished until it is removed on the insulating film in the peripheral portion of the pattern is 80 nm. It is as follows. In addition, polishing was performed for 1.5 times the required time (target polishing time) from the start of polishing until the metal film formed to be embedded in the wiring portion was removed on the insulating film (5).
The amount of dent (erosion amount) from the peripheral insulating film layer in the insulating film portion at the time of 0% over polishing does not increase more than 40 nm from the erosion amount of the target polishing time. 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. As the water-soluble polymer used in the present invention,
At least one selected from polysaccharides, polycarboxylic acids, polycarboxylic esters, salts of polycarboxylic acids, and vinyl polymers is preferred. The 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 as the protective film forming agent, a nitrogen-containing compound and a salt thereof,
At least one selected from mercaptan, glucose and cellulose is preferred. At least a part of the metal film by the step of polishing a metal film composed of a laminated film including at least one metal layer selected from copper, a copper alloy and an oxide of copper or a copper alloy using the metal polishing slurry of the present invention. Can be 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 metal polishing slurry of the present invention comprises a pattern for alternately forming a 4.5 μm-width metal embedded wiring and a 0.5 μm-width insulating film or a metal embedded wiring having a width of 1 to 10 μm and a width of 0.1 to 1 μm.
Insulating film portion polished until the metal film formed for embedding in the wiring portion is removed on the insulating film in the peripheral portion of the pattern in a pattern having a wiring pattern density of 70% or more in which the insulating film is alternately formed. Is less than 40 nm from the peripheral insulating film layer. The metal polishing slurry of the present invention comprises a metal embedded wiring having a width of 4.5 μm and a width of 0.5 μm.
A pattern or a width of 1 to 3
In a pattern having a wiring pattern density of 70% or more, in which a 10 μm metal buried wiring and an insulating film having a width of 0.1 to 1 μm are alternately formed, a metal film formed for embedding in a wiring portion from the start of polishing is formed around the pattern. Indentation amount (erosion amount) from the peripheral insulating film layer of the insulating film portion when polished (50% over-polished) for 1.5 times the time required for removal on the insulating film (target polishing time)
Is 25 nm from the erosion amount of the target polishing time.
Does not increase beyond. In the polishing method of the present invention, the polishing plate and the substrate are relatively moved 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 plate. Thus, the film to be polished can be polished.

According to the present invention, there is provided a metal polishing liquid which exhibits characteristics that the amount of erosion in a metal wiring portion having a high wiring density and the amount of increase in erosion when over-polished are small by combining a protective film forming agent and a water-soluble polymer. can do. As the protective film forming agent, a compound which easily forms a chelate complex with copper, for example, a nitrogen-containing compound such as ethylenediaminetetraacetic acid or benzotriazole is used. These metal surface protective film forming effects are extremely strong. For example, when the metal polishing liquid is contained in an amount of 0.5% by weight or more, the copper alloy film is not etched or 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 cloth was developed in contrast to the conventional effect of scraping due to the friction of solid abrasive grains. In the scraping by the friction of the polishing cloth, since the polishing of the barrier layer and the insulating film layer between the metal wirings hardly progresses, the characteristic that the erosion amount and the erosion increase amount when over-polishing is small is obtained.

The metal polishing slurry of the present invention comprises a pattern for alternately forming a 4.5 μm-wide embedded metal wiring and a 0.5 μm-wide insulating film or a metal embedded wiring having a width of 1 to 10 μm and a width of 0.1 to 10 μm. In a pattern having a wiring pattern density of 70% or more in which a 1 μm insulating film is alternately formed, the insulating film is polished until the metal film formed for embedding in the wiring portion is removed on the insulating film around the pattern. If the amount of dent (erosion amount) from the peripheral insulating film layer of the portion is 80 nm or less, the second-stage barrier layer is polished with an appropriate polishing solution, so that the wiring density generally formed is 70% or less. Good electrical characteristics can be obtained without an increase in wiring resistance due to erosion in the wiring. In this case, the erosion amount is more preferably 40 nm or less. A pattern in which 4.5 μm-wide embedded metal wiring and a 0.5 μm-wide insulating film are alternately formed, or a wiring pattern in which a 1-10 μm-wide embedded metal wiring and an 0.1-1 μm-wide insulating film are alternately formed. In a pattern with a density of 70% or more, a time 1.5 times as long as a required time (target polishing time) from the start of polishing until a metal film formed for embedding in a wiring portion is removed on an insulating film in a peripheral portion of the pattern. The dent amount (erosion amount) from the peripheral insulating film layer of the insulating film portion when polished (overpolished by 50%) does not increase more than 40 nm from the erosion amount during the target polishing time. In this case, the erosion increase is more preferably 25 nm or less.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a metal film containing copper or 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.
Since P progresses, the polishing of the barrier layer and the insulating film layer between the metal wirings hardly progresses, so that the characteristic that the erosion amount and the erosion increase amount when over-polishing are small is obtained, and the polishing scratch is also dramatically reduced. You. The metal polishing slurry of the present invention is an oxidizing agent, a metal oxide dissolving agent, a protective film forming agent,
Water-soluble polymer and water are 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 substrate 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, and 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 desirably water-soluble, and is preferably at least one selected from organic acids, organic acid esters, ammonium salts of organic acids, and sulfuric acid. 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 protective film forming agent. 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 at least one selected from nitrogen-containing compounds and salts thereof, mercaptan, glucose and cellulose. Those selected from the following groups are preferred. Ammonia; alkylamines such as dimethylamine, trimethylamine, triethylamine and propylenediamine; and amines such as ethylenediaminetetraacetic acid (EDTA), sodium diethyldithiocarbamate and 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-cystin, 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,
Amino acids such as L-histidine, 1-methyl-L-histidine, 3-methyl-L-histidine, ergothioneine, L-tryptophan, actinomycin C1, apamin, angiotensin I, angiotensin II and antipain; dithizone, cuproin (2, 2'-biquinoline), neocuproin (2,9-dimethyl-1,10
Imines such as -phenanthroline), bathocuproin (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and cuperazone (biscyclohexanone oxalylhydrazone); 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
-(1,2,4-triazolyl-1-methyl) -2-ethylhexylamine, tolyltriazole, naphthotriazole, bis [(1-benzotriazolyl) methyl]
Azoles such as phosphonic acid; mercaptans such as nonylmercaptan, dodecylmercaptan, triazinethiol, 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, naphthotriazole have high C
It is preferable to achieve both the MP rate and the low etching rate.

The water-soluble polymer is preferably at least one selected from polysaccharides, polycarboxylic acids, polycarboxylic esters, salts of polycarboxylic acids, and vinyl polymers. Those selected from the following groups are preferred. Polysaccharides such as alginic acid, pectic acid, carboxymethyl cellulose, agar, cardan 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-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, ammonium polyacrylate, sodium polyacrylate, polyamic acid, ammonium polyamic acid salt, sodium polyamic acid salt and polyglyoxyl Polycarboxylic acids such as acids 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 based on 100 g of total amount 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 0.0005 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,
The content 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, protective film forming agent, water-soluble polymer and 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 preferably a laminated film containing at least one selected from copper, a copper alloy, and an oxide of copper or a copper alloy (hereinafter referred to as 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.

In the polishing method of the present invention, the polishing platen and the substrate are relatively moved while the substrate having the film to be polished is pressed against the polishing cloth while the metal polishing liquid is supplied onto the polishing cloth of the polishing platen. This is a polishing method for polishing a film to be polished by moving the film. 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 cloth without using solid abrasive grains, so that the erosion amount and the increase amount of erosion when over-polished are small. The resulting metal polishing slurry can be provided. In the first-stage polishing of a copper alloy or the like in the two-stage polishing process, the barrier layer or the insulating film layer serves as a stopper, so that the polishing time can be easily controlled and the polishing with excellent in-plane uniformity can be realized. . 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. When benzotriazole (BTA) is treated on the metal film, especially the copper film surface, the dishing of the metal film depends on the hardness of the polishing pad and the chemical properties of the polishing liquid, depending on the particle size of the grains and the physical properties of the polishing pad. It is thought that. That is, the hard solid abrasive is CM
Although necessary for the progress of P, it is not desirable for improving the flattening effect in CMP and the integrity of the CMP surface (no damage such as polishing scratches). It can be seen that the flattening effect actually depends on the characteristics of the polishing cloth softer than the solid abrasive grains. Thus, in the present invention, it is extremely desirable for CMP of a copper alloy, and furthermore, formation of a buried pattern using the same, in that the progress of CMP is realized without solid abrasive grains. I understand.

[0031]

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). The colloidal silica used was hydrolyzed in an aqueous ammonia solution of tetraethoxysilane.

In Examples 1-4 and Comparative Examples 1-3, 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 (manufactured by Rodel)) Foamed polyurethane resin having closed cells Polishing pressure: 20.6 KPa (210 g / cm 2) Relative speed: 36 m / min (evaluation of polished product) CMP speed: The film thickness difference between 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 substrate.
As the first-stage polishing of copper, the time during which the tantalum barrier layer on silicon dioxide is just exposed over the entire surface of the substrate (overpolishing 0%) and 1.5 times the time (overpolishing 50%)
%). Wiring metal part width 10 with stylus type step meter
From the surface shape of the stripe pattern portion in which 0 μm and the insulating film portion width of 100 μm were alternately arranged, the amount of film reduction of the wiring metal portion with respect to the insulating film portion was determined. Erosion amount: Wiring metal part width 4.5 μm, insulating film part width 0.5 μm formed on the dishing amount evaluation substrate
Are measured alternately using a stylus-type profilometer to measure the surface shape of the 2.5-mm-wide stripe-shaped pattern part, which is alternately arranged. I asked. Wiring resistance: after the first-stage polishing of copper, as a second-stage polishing, a slurry for Ta barrier having a sufficiently high polishing rate ratio (Ta / Cu> 1, Ta / S)
iO ₂ > 50), after removing the Ta barrier layer,
The wiring resistance was measured. Width 1 of dishing amount measuring part
In a 00 μm copper wiring pattern, a wiring resistance value of a wiring length of 1 mm was measured. Further, in a 4.5 μm-wide copper wiring pattern of the erosion amount measuring section, a wiring resistance value of a wiring length of 1 mm was measured. Examples 1-4 and Comparative Examples 1-3
Table 1 shows polishing rates and polishing rate ratios by CMP.
Table 2 shows the amount of dishing, the amount of erosion, and the amount of increase (the amount of increase from 0% in the case of 50% overpolishing), and Table 3 shows the wiring resistance.

[0033]

[Table 1]

[0034]

[Table 2] ^* : (): Increase from 0% over-polishing

[0035]

[Table 3]

In Comparative Examples 1 and 2, although the polishing rate ratio of copper to tantalum and silicon dioxide is high, the etching rate of copper is high, so that dishing characteristics and its over-polishing resistance are particularly poor, and the wiring resistance value is low. It has increased. In Comparative Example 3, since the polishing rates of the tantalum and silicon dioxide films are relatively high, the erosion characteristics and the over-polishing resistance are particularly poor, and the wiring thickness is thin, so that the wiring resistance value is greatly increased. On the other hand, in Examples 1 to 4, the polishing rate ratio between copper and tantalum (Cu / Ta) and between copper and silicon dioxide film (Cu / SiO ₂ )
Is sufficiently large and the etching rate of copper is sufficiently low, so that the dishing amount in a 100 μm wiring is 70 nm or less, and the increase in dishing at 50% overpolishing is 30 nm or less. In addition, the wiring density is 90%.
The erosion amount at 5 μm wiring is 65 nm or less,
Erosion increase at 50% over polishing is 30n
m or less. As a result, an increase in wiring resistance due to dishing and erosion characteristics is small.

[0037]

The metal polishing slurry of the present invention makes it possible to reduce the amount of erosion in a metal wiring portion having a sufficiently high wiring density as compared with the prior art, and to provide a highly reliable metal film embedding pattern. It is possible to provide a metal polishing liquid that can be formed and a polishing method using the same.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tsuyoshi Uchida 48 Wadai, Tsukuba, Ibaraki Prefecture Within Hitachi Chemical Co., Ltd. In-house (72) Inventor Akiko Igarashi 48 Wadai, Tsukuba, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd.

Claims (12)

[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 pattern in which 4.5 μm-wide embedded metal wiring and a 0.5 μm-wide insulating film are alternately formed, or a wiring pattern in which a 1-10 μm-wide embedded metal wiring and an 0.1-1 μm-wide insulating film are alternately formed. In a pattern having a density of 70% or more, the amount of erosion (the amount of erosion from the peripheral insulating film layer of the insulating film portion when the metal film formed for embedding in the wiring portion is polished until it is removed on the insulating film in the peripheral portion of the pattern) ) Is 80 nm or less. 2. 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 pattern in which 4.5 μm-wide embedded metal wiring and a 0.5 μm-wide insulating film are alternately formed, or a wiring pattern in which a 1-10 μm-wide embedded metal wiring and an 0.1-1 μm-wide insulating film are alternately formed. In a pattern with a density of 70% or more, a time 1.5 times as long as a required time (target polishing time) from the start of polishing until a metal film formed for embedding in a wiring portion is removed on an insulating film in a peripheral portion of the pattern. A metal polishing liquid in which the amount of dent (erosion amount) from the peripheral insulating film layer of the insulating film portion when polished (overpolished by 50%) does not increase more than 40 nm from the amount of erosion during the target polishing time. 3. The weight average molecular weight of the water-soluble polymer is 500.
The metal polishing slurry according to claim 1, wherein at least one of the above is used. 4. The water-soluble polymer according to claim 1, wherein the water-soluble polymer is at least one selected from polysaccharides, polycarboxylic acids, polycarboxylic acid esters, salts of polycarboxylic acids, and vinyl polymers. Polishing liquid for metals according to the above. 5. 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. 6. 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. . 7. 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. 8. 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. 9. The metal according to claim 1, wherein a barrier layer is present below the metal to be polished, and the barrier layer is tantalum, tantalum nitride, a tantalum alloy, or another tantalum compound. Polishing liquid. 10. A pattern in which 4.5 μm wide embedded metal wiring and 0.5 μm wide insulating film are alternately formed, or a 1-10 μm wide embedded metal wiring and 0.1-1 μm wide.
Insulating film portion polished until the metal film formed for embedding in the wiring portion is removed on the insulating film in the peripheral portion of the pattern in a pattern having a wiring pattern density of 70% or more in which the insulating film is alternately formed. 2. The metal polishing slurry according to claim 1, wherein the amount of dent (erosion amount) from the peripheral insulating film layer is 40 nm or less. 11. A pattern in which a 4.5 μm-wide embedded metal wiring and a 0.5 μm-wide insulating film are alternately formed or a 1-10 μm-wide embedded metal wiring and a 0.1-1 μm wide.
In a pattern having a wiring pattern density of 70% or more in which the insulating film is alternately formed, the time required from the start of polishing until the metal film formed to be embedded in the wiring portion is removed on the insulating film around the pattern ( (Target polishing time)
Polished 5 times (50% over-polished)
The amount of erosion (erosion amount) from the peripheral insulating film layer in the insulating film portion at the time is 2 times smaller than the amount of erosion during the target polishing time.
3. The metal polishing slurry according to claim 2, wherein the polishing slurry does not increase more than 5 nm. 12. A polishing method in which a substrate having a film to be polished is pressed against the polishing cloth while the polishing liquid for metal according to claim 1 is supplied onto the polishing cloth of the polishing platen. A polishing method for polishing a film to be polished by relatively moving a surface plate and a substrate.