JP2001144043A - Polishing method for board with layered metal film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing method which can reduce a dishing value sufficiently and does not reduce a CMP speed. SOLUTION: In a polishing method, a board with a layered metal film having unevenness is pressed against a polishing cloth stuck to a polishing surface plate and, in that state, the board and the polishing surface plate are moved relatively to each other while a polishing fluid is supplied to the polishing cloth to level the unevenness. A cloth containing abrasive grains is used as the polishing cloth, and a fluid which does not contain abrasive grains or a fluid which contains abrasive grains of not more than 1% is used as the polishing fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a substrate having a metal laminated film used in a wiring step of a semiconductor device, and more particularly to a step of forming a buried wiring.

[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 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. See the Journal of Electrochemical Society (Journal of
Vol. 138, No. 11 (19)
1991), pages 3460-3364.

As a method of increasing the polishing rate by CMP, it is effective to add a metal oxide dissolving agent. It can be interpreted that dissolving the metal oxide particles removed by the solid abrasive grains in the polishing liquid increases the effect of the solid abrasive grains. However, when the 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 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. 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.

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, Thinning occurs in which the thickness of the wiring is thinned together with the interlayer insulating film.
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 technique is described in, for example, Japanese Patent No. 2819196.

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.

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,
Because the hardness and chemical properties of the films to be polished are different, compositions having considerably different properties are being studied for the composition of the polishing liquid such as pH, abrasive grains and additives.

[0013]

When buried wiring is formed by CMP using a conventional metal polishing slurry containing more than 1% by weight of solid abrasive grains, the above-mentioned abrasive grains are applied to the wiring portion of the concave portion. Dishing occurs due to contact.
The present invention reduces the amount of dishing sufficiently and
An object of the present invention is to provide a polishing method that does not lower the P speed.

[0014]

The method for polishing a substrate having a metal laminated film according to the present invention comprises: (1) pressing a substrate having a metal laminated film having an uneven surface on a polishing cloth attached to a polishing platen; In a polishing method for polishing the metal laminated film and flattening the surface irregularities by relatively moving the substrate and the polishing platen while supplying a polishing liquid onto the polishing cloth, the polishing cloth includes abrasive grains. Is a polishing method using a polishing cloth containing no, and a polishing liquid containing no abrasive grains or a polishing liquid containing 1% by weight or less of abrasive grains in the polishing liquid. (2) The polishing method according to (1), wherein the polishing liquid contains a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, a water-soluble polymer, and water.
(3) The polishing method according to (2) above, wherein the metal oxidizing agent is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water. The polishing method according to the above (2) or (3), wherein the solubilizer is at least one selected from organic acids, organic acid esters, ammonium salts of organic acids, and sulfuric acid; (5) the organic acid is malic acid; The polishing method according to the above (4), which is at least one selected from citric acid, tartaric acid, and glycolic acid, and (6) the protective film forming agent is at least one selected from benzotriazole and benzotriazole derivatives.
The polishing method according to any one of the above (2) to (5), wherein the water-soluble polymer is at least one selected from polyacrylic acid and a salt of polyacrylic acid. The polishing method according to any one of (1) to (6),
(8) The polishing method according to any one of (1) to (7), wherein the polishing cloth is at least one selected from urethane, polyethylene, polypropylene, polystyrene, polycarbonate, polytetrafluoroethylene, and ionomer; (9) The polishing method according to any one of the above (1) to (8), wherein the abrasive grains contained in the polishing cloth are at least one selected from silica, alumina, ceria, diamond, and resin, (10) abrasive grains Diameter is 1-1000n
the polishing method according to any one of (1) to (9) above, wherein (11) the metal film to be polished contains at least one selected from copper and a copper alloy.
The polishing method according to any one of (1) to (10), wherein the metal film to be polished contains at least one selected from tantalum and a tantalum alloy. (13) The polishing method according to any one of (1) to (10) above, wherein the metal film to be polished includes at least one selected from titanium and a titanium alloy.

[0015]

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 this substrate is subjected to CMP using a polishing liquid for metal containing no abrasive grains or a polishing liquid containing 1% by weight or less of abrasive grains and a polishing cloth containing abrasive grains, the metal film on the convex portion of the substrate is selectively CMPed. As a result, a desired conductor pattern is obtained by leaving the metal film in the recess. In the polishing method of the present invention,
Since the abrasive grains are fixed to the polishing pad, dishing is reduced as compared with a combination of a polishing liquid and a polishing pad containing more than 1% by weight of normal abrasive grains. The polishing liquid used in the present invention preferably contains a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, a water-soluble polymer, and water. The metal oxidizing agent used in the present invention is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid and ozone water.
Species are preferred. 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 organic acid used in the present invention is preferably at least one selected from malic acid, citric acid, tartaric acid, and glycolic acid. The protective film forming agent used in the present invention is preferably at least one selected from benzotriazole and benzotriazole derivatives. The water-soluble polymer used in the present invention is preferably at least one selected from polyacrylic acid and salts of polyacrylic acid. Polishing cloth used in the present invention, urethane, polyethylene, polypropylene, polystyrene, polycarbonate, polytetrafluoroethylene,
At least one selected from ionomers is preferred. The abrasive grains contained in the polishing cloth used in the present invention are preferably at least one selected from silica, alumina, ceria, diamond and resin. The particle size of the abrasive used in the present invention is preferably from 1 to 1000 nm. By using the polishing method of the present invention, at least a part of the metal film can be removed by a step of polishing a substrate formed of a laminated film including at least one metal layer selected from copper and a copper alloy. By using the polishing method of the present invention, at least a part of the metal film can be removed by the step of polishing a substrate formed of a laminated film including at least one metal layer selected from tantalum and a tantalum alloy. By using the polishing method of the present invention, at least a part of the metal film can be removed by a step of polishing a substrate formed of a laminated film including at least one metal layer selected from titanium and a titanium alloy.

In the polishing method of the present invention, a high CMP rate, high flatness, and dishing are achieved by using a polishing liquid containing no abrasive grains, or a polishing liquid containing 1% by weight or less of abrasive grains and a polishing cloth with fixed abrasive grains. It is possible to provide a polishing method exhibiting the effect of reducing the amount and the erosion amount.

The present inventors have found that a combined use of a polishing liquid comprising a protective film-forming agent and a water-soluble polymer and a polishing cloth containing and fixed abrasive grains enables a sufficiently suppressed dishing and a low etching rate. It has been found that a high CMP rate can be obtained while maintaining this. In addition, it has been found that by using such a polishing method, polishing can be performed at a practical CMP rate without including solid abrasive grains in the polishing liquid. This is considered to be because the effect of low etching by the conventional polishing liquid and the effect of shaving by the friction of the fixed abrasive were used in combination.

The value of the etching rate is 10 nm / m
It has been found that a preferable flattening effect can be obtained if it can be suppressed to in or less. If the decrease in the CMP rate is within an acceptable range, it is desirable that the etching rate be lower.
If it can be suppressed to not more than m / min, for example, about 50% of excess CMP (1.5 times of time required for removing the metal film by CMP).
Even if the double CMP is performed, dishing remains to the extent that no problem occurs. Further, the etching rate is 1 n
m / min or less, 100% or more of excess C
Even if MP is performed, dishing does not cause a problem. The polishing method of the present invention is preferably a polishing method using a polishing cloth containing 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 abrasive grains in combination. The polishing liquid used is adjusted so that the pH is 5 or less for copper or copper alloy and the concentration of the metal oxidizing agent is 0.01 to 30% by weight. Barrier metal (Ta, Ta
(N, Ti, TiN) is adjusted so that the pH is 3 or less and the concentration of the metal oxidizing agent is 0.01 to 3% by weight. When the pH of the polishing liquid in the present invention exceeds 3 and is large, the CMP rate of tantalum, a tantalum alloy, tantalum nitride, and other tantalum compounds becomes low. pH is
It can be adjusted by the amount added. It can also be adjusted by adding an alkali component such as ammonia, sodium hydroxide, tetramethylammonium hydride and the like.

The polishing liquid used in the present invention has a metal oxidizing agent concentration of about 0.15% by weight, and the tantalum, the tantalum alloy, the tantalum nitride and the other tantalum compounds have a C content.
The MP speed becomes maximum. The oxidizing agent forms a primary oxide layer that is easily mechanically polished on the surface of the conductive film such as tantalum, a tantalum alloy, tantalum nitride, and other tantalum compounds, so that a high CMP rate can be obtained. In general, when the pH is less than 3, the etching rate of the copper and copper alloy film is increased, so that dishing and the like are easily caused, and also the surface of the conductor film such as tantalum, tantalum alloy, tantalum nitride, and other tantalum compounds. In addition, since a secondary oxide layer that is less polished than the primary oxide layer is formed, the CMP rate is reduced. If the concentration of the oxidizing agent is less than 0.01% by weight, the oxide layer is not sufficiently formed, so that the CMP rate is reduced, and the tantalum film may be peeled off.

The metal oxidizing agent concentration in the polishing liquid is preferably 0.01 to 1.5% by weight when a water-soluble polymer is contained in the polishing liquid which is preferred in the present invention. preferable. Since the water-soluble polymer is adsorbed on tantalum, a tantalum alloy, tantalum nitride, another tantalum compound, or an oxide film surface thereof, the oxidizing agent concentration range in which a high CMP rate can be obtained is small. In addition, since the water-soluble polymer is easily adsorbed on the surface of a nitride compound film such as tantalum nitride or titanium nitride, the CMP rate of the nitride compound film such as tantalum nitride or titanium nitride decreases. On the other hand, the water-soluble polymer has a metal surface protective film forming effect, and improves flattening characteristics such as dishing and erosion. Examples of the metal oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), nitric acid, potassium periodate, hypochlorous acid, ozone water, and the like. Among them, hydrogen peroxide is particularly preferable. 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 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 and the like, and their organic acid esters, salts such as ammonium salts of organic acids, sulfuric acid, nitric acid, ammonia, ammonium salts such as ammonium persulfate; Examples thereof include ammonium nitrate and ammonium chloride, chromic acid and the like, and mixtures thereof. Among these, formic acid, malonic acid, malic acid, tartaric acid, citric acid, and glycolic acid are suitable for a laminated film containing at least one metal layer selected from copper, copper alloys, and oxides of copper or copper alloys. It is. These are preferred in that they can be easily balanced with the first and second protective film forming agents described later. In particular, malic acid,
Tartaric acid and citric acid are preferred in that the etching rate can be effectively suppressed while maintaining a practical CMP rate.

The protective film forming agent is preferably selected from the following group. Ammonia; alkylamines such as dimethylamine, trimethylamine, triethylamine and propylenediamine, and ethylenediaminetetraacetic acid (E
DTA), 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-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), bathocuproine (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.

As the water-soluble polymer, those selected from the following groups are preferred. Polysaccharides such as alginic acid, pectic acid, carboxymethyl cellulose, agar, cardran and pullulan; amino acid salts such as glycine ammonium salt and glycine sodium salt; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid , Polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyamic acid, polymaleic acid,
Polyitaconic acid, polyfumaric acid, poly (p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, ammonium polyacrylate, sodium polyacrylate, polyamic acid, ammonium polyamic acid, sodium polyamic acid And polycarboxylic acids such as polyglyoxylic acid and 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, polyacrylic acid, ammonium polyacrylate, ammonium polymethacrylate, polyacrylamide, polyvinyl alcohol and polyvinylpyrrolidone, their esters and their ammonium salts are preferred.

Examples of the polishing cloth include fluorine-containing resins such as urethane, polyethylene, polypropylene, polystyrene, polycarbonate, polytetrafluoroethylene, ionomer, ethylene-vinyl acetate copolymer (EVA), and styrene-butadiene-styrene copolymer (SBS). ), Acrylic resin, acrylonitrile-butadiene-styrene copolymer (ABS), and their foams are preferred.

As abrasive grains fixed to the polishing cloth, silica,
Alumina, ceria, diamond, and resin are preferable in that a high polishing rate can be obtained, and colloidal silica and colloidal alumina are more preferable in that scratches do not occur on the polished surface.

The particle size of the abrasive grains fixed to the polishing cloth is 1 to 10
The thickness is preferably 00 nm, and more preferably 1 to 100 nm in order to prevent scratches on the polished surface.

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, the metal oxide dissolving agent, the protective film forming agent, the 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 amounts of the metal oxide dissolving agent components are as follows: metal oxidizing agent, metal oxide dissolving agent, protective film forming agent
0-0.0 to 100 g of water-soluble polymer and water in total
It is preferable that the content be 0.05 mol, and 0.00005 to
0.0025 mol is more preferable, and 0.025 mol
It is particularly preferred that the amount be from 005 to 0.0015 mol. When the amount exceeds 0.005 mol, it tends to be difficult to suppress the etching.

The amount of the protective film forming agent is determined by the oxidizing agent of the metal,
The amount is preferably 0.0001 to 0.05 mol, more preferably 0.0003 to 0.005 mol, and more preferably 0.001 to 0.005 mol based on 100 g of the total amount of the metal oxide dissolving agent, the protective film forming agent, the water-soluble polymer, and water. 0005-0.0035
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 is determined by the metal oxidizing agent,
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, the protective film forming agent, the 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 polishing liquid used 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. The same type of water-soluble polymer or a different type of water-soluble polymer may be used.

In the polishing method of the present invention, a substrate having a film to be polished is polished while supplying a polishing liquid substantially free of the abrasive grains onto a polishing cloth of a polishing platen. This is a polishing method of polishing a film to be polished by relatively moving a polishing platen and a substrate while being pressed against a cloth. 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. 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 on the polishing cloth is 9.8 to 98 kPa (100 to 1000 kPa).
gf / cm ² ), and 9.8 to 49 kPa (100 to 500 gf / c) in order to satisfy in-plane uniformity of the CMP rate and flatness of the pattern.
m ² ) is more preferable. During polishing, a 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 polishing, the semiconductor substrate is
After washing well in running water, it is preferable to remove water droplets adhering to the semiconductor substrate by using spin drying or the like and then dry the semiconductor substrate.

[0032]

The present invention will be described below in detail with reference to examples. The present invention is not limited by these examples. (Method of preparing polishing liquid) 0.15 parts by weight of DL-malic acid (reagent grade) as a metal oxide dissolving material was dissolved by adding 70 parts by weight of water, and 0.2 parts by weight of benzotriazole as a protective film forming agent was added thereto. 0.8 part by weight of methanol solution and 0.05 part by weight (solid content) of ammonium polyacrylate as a water-soluble polymer were added. Finally, 33.2 parts by weight of aqueous hydrogen peroxide (reagent grade, 30% by weight aqueous solution) was added as a metal oxidizing agent to obtain a polishing liquid.

In Examples 1 to 4, CMP was performed using the above polishing liquid under the following polishing conditions. In the comparative example, colloidal silica (average particle diameter 100 nm) was added to the above polishing liquid.
After adding 0 parts by weight, CMP was performed under the following polishing conditions.

(Method of preparing polishing cloth) The thermoplastic polyurethane was kneaded with colloidal silica at the weight shown in the table, then wet-coagulated, and further heat-dried at 130 ° C. to obtain a polishing cloth.

(Polishing Conditions) Substrate: Silicon substrate on which a copper film having a thickness of 1 μm was formed Polishing pressure: 20.6 kPa (210 g / cm ² ) Relative speed between substrate and polishing platen: 36 m / min (polished product evaluation items) ) CMP rate: The difference in thickness of the copper film before and after the CMP was calculated from the electrical resistance value. Etching rate: The difference in the thickness of the copper layer before and after immersion in a stirred polishing liquid (room temperature, 25 ° C., 100 rpm with stirring) was calculated from the electrical resistance value. In order to evaluate dishing, CMP was performed using 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. Visual inspection of the substrate after CMP,
The presence or absence of dishing, erosion and polishing scratches was confirmed by observation with an optical microscope and observation with an electron microscope. As a result, no erosion or polishing scratches were found. Dishing: Observed with an electron microscope. Table 1 shows the results of evaluating the CMP speed and dishing in Examples 1 to 4 and Comparative Example.

[0036]

Table 1 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−− Item Polishing cloth material Contained abrasive grains Abrasive grain parts by weight CMP rate Dishing (wt%) (nm / min) (nm) ------------------------------------------------- Comparative Example 1 No urethane added-401 156 Example 1 Urethane colloidal silica 10 410 92 Example 2 Urethane colloidal silica 30 570 117 Example 3 Urethane colloidal alumina 10 460 93 Example 4 Urethane colloidal alumina 30 580 134 ---- −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

When an abrasive containing abrasive grains is used as shown in the comparative example, dishing increases. On the other hand, as shown in Examples 1 to 4, when a polishing agent containing no abrasive grains and a polishing cloth containing the abrasive grains are used in combination, polishing is performed.
Reduce dishing, despite unchanged speed.

[0038]

According to the polishing method of the present invention, dishing is reduced by using a polishing agent containing substantially no abrasive grains and a polishing cloth containing abrasive grains in combination, and a highly reliable embedded pattern can be obtained. Can be formed.

Continued on the front page (72) Inventor Tsuyoshi Uchida 48 Wadai, Tsukuba, Ibaraki Pref., Hitachi Chemical Co., Ltd. (72) Inventor Yasushi Kurata 48 Wadai, Tsukuba, Ibaraki Pref., Hitachi Chemical Co., Ltd. (72 Inventor Akiko Igarashi 48 Wadai, Tsukuba-shi, Ibaraki F-term in Hitachi Chemical Co., Ltd. Research Laboratory (reference) 3C058 AA05 AA07 AC04 CA01 CB03

Claims (13)

[Claims] 1. A substrate having a metal layered film having irregularities on its surface is pressed against a polishing cloth attached to a polishing table, and the substrate and the polishing table are relatively moved while supplying a polishing liquid onto the polishing cloth. In the polishing method for polishing the metal laminated film and flattening the surface irregularities by moving the polishing cloth, a polishing cloth containing abrasive grains is used as the polishing cloth, and the polishing liquid does not contain abrasive grains. Or, a polishing method using a polishing liquid containing 1% by weight or less of abrasive grains. 2. The polishing method according to claim 1, wherein the polishing liquid contains a metal oxidizing agent, a metal oxide dissolving agent, a protective film forming agent, a water-soluble polymer, and water. 3. The polishing method according to claim 2, wherein the metal oxidizing agent is at least one selected from hydrogen peroxide, nitric acid, potassium periodate, hypochlorous acid, and ozone water. 4. The polishing method according to claim 2, 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. 5. The polishing method according to claim 4, wherein the organic acid is at least one selected from malic acid, citric acid, tartaric acid, and glycolic acid. 6. The protective film forming agent is at least one selected from benzotriazole and benzotriazole derivatives.
The polishing method according to any one of claims 2 to 5, which is a seed. 7. The polishing method according to claim 2, wherein the water-soluble polymer is at least one selected from polyacrylic acid and a salt of polyacrylic acid. 8. The polishing method according to claim 1, wherein the polishing cloth is at least one selected from urethane, polyethylene, polypropylene, polystyrene, polycarbonate, polytetrafluoroethylene, and ionomer. 9. The polishing method according to claim 1, wherein the abrasive grains contained in the polishing cloth are at least one selected from silica, alumina, ceria, diamond, and resin. 10. The polishing method according to claim 1, wherein the abrasive has a particle size of 1 to 1000 nm. 11. The metal film to be polished includes at least one selected from copper and copper alloy.
0. The polishing method according to any one of 0. 12. The polishing method according to claim 1, wherein the metal film to be polished includes at least one selected from tantalum and a tantalum alloy. 13. The polishing method according to claim 1, wherein the metal film to be polished contains at least one selected from titanium and a titanium alloy.