JP2000195831A - Metal polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a highly reliable metal film-buried pattern by a method, wherein a metal polishing method uses an enriched liquid which is diluted, obtained by enriching an abrasive liquid for a metal containing a metallic oxidizing agent, a metal oxide solution agent, a protective film forming agent and water. SOLUTION: This method include 70 pts.wt. of water is added to 1.5 pts.wt. of a benzotriazole, and the benzotriazole is stirred in a hot water bath of 40 deg.C by a stirring vane and the water is dissolved in the benzotriazole. Continuingly, 0.5 pts.wt. (protective film forming agent) of a 4-carboxylbenzotriazole and 1.5 pts.wt. (metal oxide disolving agent) of a DL-malic acid (special grade reagent) are added to the benzotriazole to dissolve the 4-carboxylbenzotriazole and the DL-malic acid in the benzotriazole, and the obtained is used as an enriched liquid enriched at a concentration 10 times higher than the concentration of the benzotriazole. Then 63 pts.wt. of water is added to the obtained enriched liquid 7 to dissolve in the liquid 7, and the obtained solution by adding 33.2 pts.wt. (metal oxidizing agent) of hydrogen peroxide solution (special grade reagent, 30% aqueous solution) to that obtained by dissolving the water in the liquid 7 is used as an abrasive liquid for metals. This abrasive liquid is used, and chemical and mechanical polishing is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal polishing liquid and a polishing method in a wiring process 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. 4944836
Is disclosed.

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 pad to a circular polishing platen (platen), immerse the surface of the polishing pad 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. The details are disclosed in Journal of Electrochemical Society, Vol. 138, No. 11, published in 1991, pp. 3460-3364.

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 an oxidizing agent. When this is repeated, the etching of the metal film in the recess proceeds. Thus, there is a concern 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 a chemical reaction effect, the CMP speed (polishing speed by CMP) is improved, and the CMP speed is improved.
The effect that the damage (damage) of the metal layer surface to be performed is also reduced 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. Generation of a dish-like phenomenon (hereinafter referred to as dishing), (2) generation of polishing scratches (scratch) derived from solid abrasive grains, and (3) removal of solid abrasive grains remaining on the substrate surface after polishing. The cleaning process is complicated, and (4) the cost of the solid abrasive grains itself and the cost increase due to the waste liquid treatment arise.

The above problem (4) can be improved by reducing the production cost of the polishing solution maker by using the concentrated solution of the metal polishing solution, and consequently by reducing the cost of the diluted solution. It is. In addition, since the use of the concentrated solution eliminates the need to increase the scale of the polishing liquid production equipment, there is an advantage that it is possible to cope with mass production without investing in new equipment. In consideration of the effect obtained by using the concentrated solution, it is desirable that the concentrated solution can be prepared ten times or more.

[0010] In order to suppress 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 amidosulfuric acid such as glycine and BTA (benzotriazole) are contained. A method using a metal polishing solution has been proposed. This technique is described in, for example, JP-A-8-83780.

[0011]

However, since the solubility of BTA in water is low (2 g / 20 ° C. water 100c).
c) In the polishing solution for a specific metal, the target concentration of 10 times could not be concentrated (for example, the concentration of a metal polishing solution containing 0.2% by weight of BTA can be increased up to 5 times, and in the case of 10 times, precipitation at room temperature of 10 ° C. or less). . Therefore, the polishing liquid can be concentrated 10 times or more,
In addition, there has been a demand for a metal polishing solution that does not precipitate BTA in a concentrated solution in a normal environment at room temperature of 0 ° C. or higher. SUMMARY OF THE INVENTION The present invention provides a metal polishing method characterized by diluting a concentrated solution of a metal polishing liquid and enabling formation of a highly reliable embedded pattern of a metal film.

[0012]

According to the metal polishing method of the present invention, a concentrated metal polishing solution containing a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent and water is diluted and used. It is characterized by. It is preferable to add a protective film forming agent having a hydrophilic group to the concentrate of the metal polishing solution. The metal polishing liquid of the present invention contains a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, and water. The protective film forming agent forms a protective film on the metal surface, and is preferably at least one selected from nitrogen-containing compounds such as ammonia, alkylamines, amino acids, imines and azoles and salts thereof, and mercaptan, glucose and cellulose.

The oxidizing agent is preferably at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid and ozone water. As a metal oxide dissolving agent,
At least one selected from organic acids, ammonium salts thereof, and sulfuric acid is preferred. The polishing method of the present invention is a step of polishing a metal film made 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 above-mentioned metal polishing liquid. Is a polishing method for removing at least a part of the metal film.

The value of the etching rate to be suppressed is 1
It has been found that a preferable flattening effect can be obtained if it can be suppressed to 0 nm / min or less. If the decrease in the CMP rate is within an acceptable range, it is desirable that the etching rate be even lower, and if it can be suppressed to 5 nm / min or less, for example, 50%
Even if an excessive amount of CMP is performed (performing CMP 1.5 times as long as the time required for removing the metal film by CMP), dishing is not a 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. The etching rate is an etching rate of a metal film when a substrate to be polished (a substrate in which a metal film is formed and filled on a substrate having a concave portion on the surface) is immersed in a polishing liquid and stirred at 100 rpm at room temperature. The difference in film thickness is obtained by converting from the electric resistance value.

[0015]

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 this substrate is subjected to CMP using the polishing liquid according to the present invention, the metal film on the convex portion of the substrate is selectively subjected to the CMP.
By performing the MP, the metal film is left in the concave portion to obtain a desired conductor pattern. The polishing liquid of the present invention may be substantially free of solid abrasive grains, and polishing scratches are dramatically reduced because CMP proceeds by friction with a polishing pad that is much more mechanically softer than solid abrasive grains. . The metal polishing slurry of the present invention contains an oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, and water as essential components. Solid abrasive particles need not be substantially contained, but may be used.

As a metal oxidizing agent, 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 containing no 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 because they can be easily balanced with a protective film forming agent 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 added protective film forming agent is preferably selected from the following group. Ammonia, dimethylamine, trimethylamine, triethylamine, propylenediamine, ethylenediaminetetraacetic acid (EDTA),
Ammonia and alkylamines such as 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-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-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, L-histidine, 1-methyl-L-histidine, 3
Amino acids such as -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-phenanthroline), bathocuproine (2,9-
Imines such as 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-1,2,4-triazole, benzotriazole, 1
-Hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4-carboxylbenzotriazole, 4-carboxylbenzotriazole methyl ester, 4-
Carboxylbenzotriazole butyl ester, 4-
Carboxylbenzotriazole octyl ester, 5
-Hexylbenzotriazole, [1,2,3-benzotriazolyl-1-methyl] [1,2,4-triazolyl-1-methyl] [2-ethylhexyl] amine, tolyltriazole, naphthotriazole, bis [( Azoles such as 1-benzotriazolyl) methyl] phosphonic acid;
Mercaptans such as nonyl mercaptan and dodecyl mercaptan; and glucose, cellulose and the like. Among them, benzimidazole-2-thiol,
Triazinedithiol, triazinetrithiol, 2-
[2- (benzothiazolyl) thiopropionic acid, 2-
[2- (benzothiazolyl) thiobutyric acid, 2-mercaptobenzothiazole), 1-hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4-carboxylbenzotriazole , 4-carboxylbenzotriazolemethyl ester, 4-carboxylbenzotriazolebutyl ester, 4-carboxylbenzotriazoleoctyl ester, and bis [(1-benzotriazolyl) methyl] phosphonic acid are preferred because they have a hydrophilic group.

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 (hereinafter, referred to as a copper alloy).

The amount of the oxidizing agent is based on 100 g of the total amount of the oxidizing agent, the metal oxide dissolving agent, the protective film forming agent and the water.
It is preferably from 0.003 mol to 0.7 mol, more preferably from 0.03 mol to 0.5 mol, and particularly preferably from 0.2 mol to 0.3 mol. If the amount is less than 0.003 mol,
Insufficient metal oxidation, low CMP rate, 0.7mol
If it exceeds, the polished surface tends to be rough.

The compounding amount of the metal oxide dissolving agent component in the present invention is preferably 0 to 0.005 mol, preferably 0.00005 mol, per 100 g of the total amount of the oxidizing agent, the metal oxide dissolving agent, the protective film forming agent and water. ~ 0.0025mo
1 is more preferable, and 0.0005 mol or more.
It is particularly preferred that the content be 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 is preferably 0.0001 mol to 0.05 mol based on 100 g of the total amount of the oxidizing agent, the metal oxide dissolving agent, the protective film forming agent and water. 005 mol, more preferably 0.0005 mol to 0.0035 m
ol is particularly preferred. This compounding amount is 0.00
If it is less than 01 mol, it tends to be difficult to suppress etching, and if it exceeds 0.05 mol, the CMP rate tends to be low. Further, among the protective film forming agents used in preparing the concentrated liquid, those having a solubility in water at room temperature of less than 5% are preferably mixed with water at room temperature within twice as much as 1.5%. More preferably, it is within a factor of two. If the blending amount is more than twice, concentrate
It is difficult to prevent precipitation when cooled to a low temperature.

[0023]

According to the present invention, unlike the conventional polishing liquid, it is possible to provide a metal polishing method for reducing the production cost of the metal polishing liquid by using a concentrated solution of the metal polishing liquid.
In this polishing liquid, a protective film forming agent having a hydrophilic group can be used alone or in combination as needed. As a result, the function of forming the protective film is reduced, but it is possible to prepare a broader and higher-concentration metal-polishing liquid in accordance with desired polishing characteristics.

[0024]

The present invention will be described below with reference to examples. The present invention is not limited by these examples. Example 1 70 parts by weight of water was added to 1.5 parts by weight of benzotriazole, and the mixture was dissolved by stirring with a stirring blade in a 40 ° C. water bath. Subsequently, 0.5 parts by weight of 4-carboxybenzotriazole DL-
1.5 parts by weight of malic acid (special grade reagent) was added and dissolved to obtain a 10-fold concentrated solution. Next, 63 parts by weight of water was added to and dissolved in 7 parts by weight of the obtained concentrated liquid, and 33.2 parts by weight of hydrogen peroxide (special grade reagent, 30% aqueous solution) was added thereto. Polishing liquid. Using the above metal polishing liquid, CMP was performed under the following polishing conditions. << Polishing Condition >> Base: Silicon substrate on which copper film of 1 μm thickness was formed Polishing pad: IC1000 (manufactured by Rodale) Polishing pressure: 210 g / cm ² Relative speed between substrate and polishing platen: 36 m / min << Polishing product evaluation Item> CMP rate: The difference in film thickness before and after the CMP of the copper film was calculated from the electrical resistance value. Etching rate: The difference in the thickness of the copper layer before and after immersion in the agitated polishing liquid was determined by converting from the electrical resistance value. Also, the actual CM
In order to evaluate the P characteristics, CMP was also performed on a silicon substrate in which a groove having a depth of 0.5 μm was formed in the insulating layer, a copper film was formed by a known sputtering method, and embedded by a known heat treatment, as a base. Was. The presence or absence of erosion and polishing scratches was confirmed by visual observation, optical microscope observation, and electron microscope observation of the substrate after CMP. As a result, no erosion or polishing scratches were found. As a result, the CMP rate was 181 nm / min, and the etching rate was 0.4 nm / min.

Example 2 70 parts by weight of water was added to 2 parts by weight of triazine thiol, and
The mixture was stirred and dissolved in a 0 ° C. water bath with a stirring blade. Then DL-
Tartaric acid (special grade reagent) was added and dissolved in 1.5 parts by weight to obtain a 10-fold concentrated solution. Next, the obtained concentrated solution 7
63 parts by weight of water was added to and dissolved in parts by weight, and 33.2 parts by weight of hydrogen peroxide solution (special grade reagent, 30% aqueous solution) was added thereto, and the resultant was used as a metal polishing slurry. Using the above metal polishing liquid, CMP was performed under the same CMP conditions as in Example 1. As a result, the CMP rate was 188 nm / min, and the etching rate was 0.9 nm / min. Erosion and polishing scratches were not observed.

Comparative Example 1 The metal polishing slurry was prepared by the following method without the concentration step in the metal polishing slurry preparation process of Example 1. 70 parts by weight of water was added to 0.15 parts by weight of benzotriazole, and the mixture was stirred and dissolved in a 40 ° C. water bath with a stirring blade. Further, 0.05 parts by weight of 4-carboxybenzotriazole and 0.15 parts by weight of DL-malic acid (special grade reagent) were added and dissolved. Finally, 33.2 parts by weight of a hydrogen peroxide solution (reagent grade, 30% aqueous solution) was added to obtain a polishing liquid for metal. Using the above-mentioned metal polishing liquid, the same CMP conditions as in Example 1 were applied to the CM.
P was applied. As a result, the CMP speed becomes 182 nm / mi.
n, the etching rate was also good at 0.4 nm / min, and there was no difference between the CMP rate and the etching rate depending on the presence or absence of the concentration step. Erosion and polishing scratches were not observed.

Comparative Example 2 A 10-fold concentrated liquid was prepared by dissolving 2 parts by weight of benzotriazole in the polishing liquid for metal of Example 1 without adding 4-carboxybenzotriazole. However, when this was refrigerated and stored at 5 ° C., a deposit was generated, which made it difficult to evaluate the metal polishing slurry.

[0028]

According to the metal polishing method of the present invention, a metal polishing liquid can be concentrated, and a highly reliable metal film embedding pattern can be formed.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroki Terasaki 48 Wadai, Tsukuba, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. Within the Research Laboratory (72) Inventor Naoyuki Koyama 48 Wadai, Tsukuba, Ibaraki Prefecture F-term within the Tsukuba Development Laboratory, Hitachi Chemical Co., Ltd.

Claims (2)

[Claims] 1. A metal polishing method comprising diluting a concentrated metal polishing solution containing a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent and water. 2. The metal polishing method according to claim 1, wherein a protective film-forming agent having a hydrophilic group is added to the concentrate of the metal polishing liquid.