JP2001127017A - Metal polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal polishing method for discovering a high CMP rate, and for realizing high flattening, dishing amount reduction, and erosion amount reduction, and for executing high reliable metallic film embedding pattern formation. SOLUTION: This is a metal polishing method for polishing a metallic film on a substrate by using nonwoven fabric as polishing cloth while supplying polishing fluid for metal containing an oxidizer for metal, metal oxide dissolving agent, protecting film forming agent, and water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal polishing method, and more particularly to a metal polishing method suitable for a wiring step of a semiconductor device.

[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 (hereinafter, referred to as LSI). Chemical mechanical polishing (hereinafter referred to as CMP)
The method is one of them. For example, in an LSI manufacturing process, particularly, in a multilayer wiring forming process, an interlayer insulating film is flattened, a metal plug is formed,
This is a technique frequently used in the formation of embedded wiring. 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 on a circular polishing platen (platen), soak the surface of the polishing cloth with a metal polishing solution, and press the surface of the substrate on which the metal film is formed. Then, the polishing platen is rotated while applying a predetermined pressure (hereinafter, referred to as a polishing pressure) from the back surface, and the metal film of the convex portion is removed by mechanical friction between the polishing liquid and the convex portion of the metal film. is there.

[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
Electrochemical Society), Vol. 138, No. 11 (issued in 1991), pp. 3460-3346.

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 oxide layer on the surface of the metal film in the recess is also dissolved (hereinafter referred to as etching) and the surface of the metal film is exposed, the surface of the metal film is further oxidized by the oxidizing agent. 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 damage to the surface of the metal layer subjected to P is also 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 (hereinafter referred to as dishing) occurs. (2) The phenomenon in which not only the metal wiring but also the underlying insulating film is polished in a portion where the metal wiring interval is narrow and the wiring density is high (hereinafter, erosion). (3) occurrence of polishing scratches derived from solid abrasive grains, (4) complicated cleaning process for removing solid abrasive grains remaining on the substrate surface after polishing, (5) Problems such as the cost of the solid abrasive grains themselves and the cost increase due to waste liquid treatment arise.

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 in which the thickness of the wiring together with the interlayer insulating film becomes thin easily occurs. 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, in order to suppress the polishing rate of silicon dioxide by anions generated by dissociation of an acid, a method has been proposed in which the pH of the polishing liquid is made higher than pKa-0.5. This technology is disclosed, for example, in Japanese Patent No. 28191.
No. 96.

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. 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.

[0012]

SUMMARY OF THE INVENTION The invention according to claims 1 to 7 provides a highly reliable metal film embedding pattern which exhibits a high CMP rate, enables high flattening, reduces the amount of dishing and reduces the amount of erosion. The present invention provides a metal polishing method capable of forming a metal layer.

[0013]

According to the present invention, a metal polishing agent containing a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent and water is supplied to a substrate while supplying the metal polishing liquid. The present invention relates to a metal polishing method, characterized in that the metal film is polished using a nonwoven fabric as a polishing cloth. The present invention also relates to the metal polishing method, wherein the metal polishing liquid further contains a water-soluble polymer. The present invention also relates to the metal polishing method, wherein the metal oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, potassium iodate, and ozone water.

The present invention also relates to the above metal polishing method, wherein the metal oxide dissolving agent is at least one selected from the group consisting of organic acids, organic acid esters, ammonium salts of organic acids, and inorganic acids. Further, the present invention, the protective film forming agent is a nitrogen-containing compound, a salt of the nitrogen-containing compound, mercaptan,
The present invention relates to the metal polishing method, which is at least one selected from the group consisting of glucose and cellulose.

Further, according to the present invention, the metal film to be polished is
The present invention relates to the metal polishing method including at least one selected from the group consisting of copper, copper alloy, copper oxide, and copper alloy oxide. The present invention also relates to the metal polishing method, wherein the water-soluble polymer includes at least one selected from the group consisting of polyacrylic acid and polyacrylate.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION As the metal oxidizing agent in the present invention, hydrogen peroxide (H ₂ O ₂ ), potassium periodate, ozone water and the like can be mentioned, among 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 containing no semiconductor element, an oxidizing agent containing a nonvolatile component may be used.

As the metal oxide dissolving agent in the present invention,
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,
Organic acids such as adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, esters of these organic acids, ammonium salts of these organic acids, sulfuric acid, nitric acid,
Examples include inorganic acids such as hydrochloric acid, hypochlorous acid, and chromic acid, and ammonium salts such as ammonium persulfate, ammonium nitrate, and ammonium chloride. Among these, formic acid, malonic acid, malic acid, tartaric acid, citric acid and the like are preferable. In particular, an organic acid having two or more carboxyl groups in a molecule such as malic acid, tartaric acid, or citric acid is preferable in that the etching rate can be effectively suppressed while maintaining a practical CMP rate.

As the protective film forming agent in the present invention, dimethylamine, trimethylamine, triethylamine,
Propylenediamine, ethylenediaminetetraacetic acid (E
DTA), sodium diethyldithiocarbamate, alkylamines 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-diiodo-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-
Amino acids such as 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), bathocuproine (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) and cuperazone (biscyclohexanone oxalylhydrazone); benzimidazole-2-
Thiol, triazinedithiol, triazinetrithiol, 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-) benzotriazo- 4-Carboxyl (-1H-) benzotriazo-
Methyl carboxylate, 4-carboxyl (-1H-) benzotriazole-butyl ester, 4-carboxyl (-1H-) benzotriazole-octyl ester, 5
-Hexylbenzotriazole, [1,2,3-benzotriazolyl-1-methyl] [1,2,4-triazolyl-1-methyl] [2-ethylhexyl] amine, tolyltriazole, naphthotriazo- And nitrogen-containing compounds such as azoles such as bis [(1-benzotriazolyl) methyl] phosphonic acid; salts of nitrogen-containing compounds; mercaptans such as nonylmercaptan and dodecylmercaptan; glucose and cellulose. Is mentioned.

Among them, chitosan, ethylenediaminetetraacetic acid, L-tryptophan, cuperazone, triazinedithiol, benzotriazole, 4-hydroxybenzotriazole, and 4-carboxyl are preferred in terms of achieving both a CMP rate and a low etching rate. (-1H-) benzotriazole butyl ester, tolyltriazole,
Naphthotriazole and the like are preferred.

The polishing slurry for metals of the present invention may contain a water-soluble polymer as required from the viewpoint of suppressing etching (suppressing dissolution of an undesired metal when the polishing pad is not relatively moved). Can be. Examples of the water-soluble polymer in the present invention include 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 and polyglutamic acid , Polylysine, polymalic acid, polymethacrylic acid, ammonium polymethacrylate, sodium polymethacrylate, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, Amino polyacrylamide, ammonium polyacrylate,
Polycarboxylic acids and salts thereof such as sodium polyacrylate, polyamic acid, ammonium polyamic acid, sodium polyamic acid and polyglyoxylic acid; and vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein. . Among them, polycarboxylic acids and salts of polycarboxylic acids are preferred, and polyacrylic acids and polyacrylates are particularly preferred.

In the present invention, the amount of the metal oxidizing agent is as follows:
The metal oxidizing agent, the metal oxide dissolving agent, the protective film forming agent, the water-soluble polymer and the water used as required, preferably 100 parts by weight of water, preferably 0.1 to 25 parts by weight,
It is more preferably from 1 to 20 parts by weight, particularly preferably from 6 to 11 parts by weight. If the amount is less than 0.1 part by weight, metal oxidation is insufficient and the CMP rate is low, and if it exceeds 20 parts by weight, the polished surface tends to be rough.

The amount of the metal oxide dissolving agent used in the present invention is based on 100 parts by weight of the total amount of the metal oxidizing agent, the metal oxide dissolving agent, the protective film forming agent, the water-soluble polymer used as required, and water. It is preferably 0.001 to 1 part by weight, more preferably 0.005 to 0.5 part by weight, and particularly preferably 0.05 to 0.3 part by weight. If the amount exceeds 1 part by weight, it tends to be difficult to suppress etching.

The compounding amount of the protective film forming agent in the present invention is as follows:
It is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of the metal oxidizing agent, the metal oxide dissolving agent, the protective film forming agent, and the water-soluble polymer and water used as required. More preferably, the amount is from 03 to 1 part by weight,
It is particularly preferred that the amount be 0.05 to 0.5 part by weight. If the amount is less than 0.01 part by weight, it tends to be difficult to suppress the etching.
Speed tends to be lower.

The amount of the water-soluble polymer used as required in the present invention may be selected from the group consisting of a metal oxidizing agent, a metal oxide dissolving agent,
The amount is preferably 0.001 to 0.3 parts by weight, more preferably 0.003 to 0.1 parts by weight, based on 100 parts by weight of the total amount of the protective film forming agent, the water-soluble polymer and the water. It is particularly preferably 0.01 to 0.08 parts by weight. When the amount is less than 0.001 part by weight, the effect of using the protective film forming agent in combination tends not to be exhibited in suppressing etching, and when the amount exceeds 0.3 part by weight, CM
The P speed tends to decrease.

The weight-average molecular weight of the water-soluble polymer (a value measured by gel permeation chromatography and converted into polystyrene) is preferably 500 or more, and 1500 or more.
More preferably, it is more 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. When the weight average molecular weight is less than 500, a high CMP rate tends not to be developed. In the present invention, it is preferable to use at least two kinds of water-soluble polymers having a weight average molecular weight of 500 or more and different weight average molecular weights. Further, the same type of water-soluble polymer or a different type of water-soluble polymer may be used.

The metal polishing slurry of the present invention may contain abrasive grains such as silica, if necessary. Further, ammonia may be added to adjust the pH.

The substrate to be polished in the present invention is not particularly limited as long as it has a metal film, but copper, copper alloy (such as copper / chromium), copper oxide, A substrate on which a metal film containing an object or a copper alloy oxide is formed and filled can be suitably polished. When such a substrate is polished using the metal polishing liquid of the present invention, the metal film on the convex portion of the substrate is selectively polished and removed, and a desired flattened wiring pattern is obtained.

In 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 the metal polishing liquid is supplied onto the polishing cloth of the polishing plate. Thus, the film to be polished can be polished. By polishing a nonwoven fabric as a polishing cloth using a specific metal polishing liquid, the dishing and erosion amounts can be reduced while maintaining a practical polishing rate. In the present invention, the nonwoven fabric is a polishing cloth. Non-woven fabrics do not exhibit the excellent polishing characteristics of the present invention such as a high polishing rate, a low etching rate, and low dishing and erosion. The nonwoven fabric is not particularly limited, and a known material can be used. For example, a nonwoven fabric made of polyurethane can be used.

As a polishing apparatus, a general polishing apparatus having a holder for holding a semiconductor substrate and a platen on which a polishing cloth is attached (a motor or the like whose rotation speed can be changed) is mounted can be used. As the polishing cloth, nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used. The polishing conditions are not limited, but the rotation speed of the platen is preferably low, such as 200 m ^-1 or less so that the substrate does not pop out. The pressing pressure of the substrate having the film to be polished against the polishing cloth is 9800.
The pressure is preferably 9800 Pa to 98000 Pa, and more preferably 9800 Pa to 49000 Pa in order to satisfy the uniformity of the CMP rate in the wafer surface and the flatness of the pattern. 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 substrate is preferably washed well in running water, and then dried by removing water droplets attached to the semiconductor substrate using spin drying or the like.

[0030]

The present invention will be described below with reference to examples. The present invention is not limited by these examples.

Examples 1-4 and Comparative Examples 1-2 (Preparation of polishing liquid) Tartaric acid, DL-
Malic acid, citric acid, benzotriazole as a protective film forming agent, and ammonium polyacrylate and polyacrylylamide as water-soluble polymers were used. Hydrogen peroxide (30% by weight aqueous solution) was used as a metal oxidizing agent. The composition is shown in Table 1. (Abrasive cloth) As the abrasive cloth, those made of foamed polyurethane (Comparative Examples 1 to 4) and polyurethane nonwoven fabric (Examples 1 to 4)
4) was used. Table 2 shows the combinations with the studied polishing liquids.

(Polishing Conditions) (1) Substrate: Silicon substrate (blanket wafer and TEG) on which a copper film having a thickness of 1 μm is formed (2) Polishing pressure: 21000 Pa (3) Relative speed between substrate and polishing platen: 36 m / min (4) Polishing liquid supply: 200 ml / min

The polished products obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated according to the following evaluation items.
It was shown to. (Evaluated items of polished product) (1) Polishing rate (CMP rate): The difference in film thickness of the copper film before and after the CMP was calculated from the electrical resistance value. (2) Etching rate: stirring metal polishing liquid (room temperature,
The difference in the thickness of the copper layer before and after immersion in 25 ° C. and stirring at 100 m ⁻¹ ) was determined by converting from the electrical resistance value.

(3) Dishing: Polishing was performed using a TEG pattern until the barrier metal was reached, and dishing with a line and space of 100 μm was measured. The measurement was performed by taking a cross-sectional photograph of the TEG pattern using a scanning electron microscope (SEM). FIG. 1 shows a cross-sectional structure of the measurement unit. (4) Erosion: Polishing is performed using a TEG pattern until the barrier metal is reached, and the line & space is 1 μm.
The erosion of the part was measured. Figure 2 shows the cross-sectional structure of the measuring part.
Shown in The erosion was measured using a stylus-type step meter.

[0035]

[Table 1]

[0036]

[Table 2]

As shown in Examples 1 to 4, polishing by using a non-woven fabric as a polishing cloth provides a practical level of 10%.
It has a polishing rate of 0 (nm / min) or more, and has dishing and erosion of 220 (nm) or less, so that it can be put to practical use. On the other hand, in the case of Comparative Examples 1 to 4 using a foamed polyurethane type, the polishing rate is lower, and dishing and erosion are large.

[0038]

According to the metal polishing method of the present invention, a high CMP rate is achieved, high flattening, reduction of dishing amount and reduction of erosion amount are achieved, and a highly reliable pattern for burying a metal film. It enables formation.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of dishing in an embodiment.

FIG. 2 is a schematic diagram showing a cross-sectional structure of an erosion in the embodiment.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) C09K 13/00 C09K 13/00 (72) Inventor Yasuo Uegami 48 Wadai, Tsukuba-shi, Ibaraki Pref. Hitachi Chemical Co., Ltd. (72) Inventor Hiroki Terasaki 48 Wadai, Tsukuba, Ibaraki Prefecture, Hitachi Chemical Co., Ltd. (72) Inventor Yasushi Kurata 48 Wadai, Tsukuba, Ibaraki Prefecture, Hitachi Chemical Co., Ltd. F-term (reference) 3C058 AA07 AA09 CB02 CB03 DA02 DA12 DA17

Claims (7)

[Claims] 1. A nonwoven fabric polishing cloth for a metal film on a substrate using a metal polishing liquid containing a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent and water, and supplying the metal polishing liquid. A metal polishing method, characterized in that polishing is performed as follows. 2. The metal polishing method according to claim 1, wherein the metal polishing liquid further contains a water-soluble polymer. 3. The metal polishing method according to claim 1, wherein the metal oxidizing agent is at least one selected from the group consisting of hydrogen peroxide, potassium periodate, and ozone water. 4. The metal polishing method according to claim 1, wherein the metal oxide dissolving agent is at least one selected from the group consisting of organic acids, organic acid esters, ammonium salts of organic acids, and inorganic acids. 5. The protective film-forming agent is at least one selected from the group consisting of nitrogen-containing compounds, salts of nitrogen-containing compounds, mercaptans, glucose and cellulose.
5. The metal polishing method according to any one of items 1 to 4. 6. The metal polishing method according to claim 1, wherein the metal film to be polished includes at least one selected from the group consisting of copper, copper alloy, copper oxide and copper alloy oxide. 7. The metal polishing method according to claim 2, wherein the water-soluble polymer contains at least one selected from the group consisting of polyacrylic acid and polyacrylate.