JP2003282494A - Composition for polishing metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for polishing a metal, a planarization method and a semiconductor substrate manufacturing method of a metal film on a semiconductor substrate using a composition having the capability to polish fast a metal film even under a low-load condition and further to restrain defect such as scratches dishings or the like from generating on polished surfaces. <P>SOLUTION: The composition for polishing the metal is characterized by being composed of a polyoxoacid and/or its salt, a water-soluble polymer and water. A planarization method and a semiconductor substrate manufacturing method of the metal film on a semiconductor substrate using the composition are provided. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polishing composition used for polishing a metal film formed on a semiconductor substrate, a method for polishing a metal film on a semiconductor substrate using the same, and a method for producing a semiconductor substrate. Regarding the method.

[0002]

2. Description of the Related Art Due to the rapid development of LSI technology, integrated circuits are becoming more and more miniaturized and multilayer wiring is being used. Multi-layer wiring in integrated circuits is a factor that makes semiconductor surface irregularities extremely large, which, in combination with the miniaturization of integrated circuits, causes disconnection, lowering of electric capacity, occurrence of electromigration, etc., which leads to lower yield and reliability. Cause the problem of.

Therefore, various processing techniques for flattening the metal wiring and the interlayer insulating film in the multilayer wiring board have been developed so far, and one of them is CMP (Chemical Mec).
hanical Polishing: chemical mechanical polishing) technology. C
MP technology is used to flatten the interlayer insulating film in semiconductor manufacturing,
This is a technique required for forming embedded wiring, forming a plug, and the like. CMP is performed by rotating a carrier and polishing pad, respectively, while pressing a flat wafer, usually made of semiconductor material, mounted on the carrier against a wet polishing pad with a constant pressure.
At this time, the projections of the wiring and the insulating film are polished and planarized by the polishing composition introduced between the wafer and the polishing pad.

Conventionally, various polishing compositions and polishing methods have been proposed for polishing a metal film on a semiconductor substrate. Toshio Doi et al. "Semiconductor flattening CMP technology" (July 1998,
As published on page 235 of the Industrial Research Board, in CMP of metals, the surface of the metal is oxidized and passivated by the oxidizing agent in the polishing composition, and the metal is slightly acidified by making the pH acidic. Polishing is performed with a polishing pad and abrasive grains under the condition of being corroded (etching). For example, as a polishing composition for a metal film such as aluminum formed on a semiconductor substrate,
A polishing composition (US Pat. No. 4,702,792) in which aluminum oxide is dispersed in a nitric acid aqueous solution having a pH of 3 or less, aluminum oxide or silicon oxide is mixed with an acidic aqueous solution such as sulfuric acid, nitric acid or acetic acid. Is a polishing composition (US Pat. No. 4,944,836). Further, a polishing composition in which aluminum oxide is dispersed in hydrogen peroxide and a phosphoric acid aqueous solution (US Pat. No. 5,209,816), etc.
A polishing composition comprising abrasive grains such as aluminum oxide or silicon oxide and an oxidizing agent such as hydrogen peroxide is usually used. However, when aluminum oxide is used to planarize the metal film on the semiconductor substrate, the α-type shows a high polishing rate, but on the other hand, defects such as micro scratches and orange peel can be generated on the surface of the metal film or the insulating film. there were.
On the other hand, when abrasive grains such as γ type or amorphous alumina or silicon oxide are used, it is possible to suppress the occurrence of defects such as micro scratches and orange peel on the surface of the metal film or the insulating film, but when polishing the metal film. There is a problem that a sufficient polishing rate cannot be obtained. As described above, the polishing composition in which the abrasive particles made of a metal oxide such as aluminum oxide or silicon oxide are dispersed in the aqueous solution has a problem of surface scratch due to poor dispersibility of the abrasive particles themselves. In addition, as described above, when hydrogen peroxide, which is a liquid oxidizing agent, is used, or when a metal etchant such as ammonium persulfate is used (JP-A-6-313164), wet etching proceeds excessively. By doing this, dishing (Fig. 1
(D) The central portion of the metal film 4 is excessively polished from the peripheral portion) and defects such as pits and voids are generated, which is a problem in practical use.

For the purpose of improving this, a method of adding a chemical reagent (corrosion inhibitor, chelating agent, etc.) for forming a protective film on the surface of a metal film in a polishing composition has also been proposed (JP-A-8-
83780, JP-A-11-195628). However, with such chelating agents,
Although the etching is surely suppressed and the occurrence of dishing or the like can be prevented, a problem arises that the polishing rate is extremely lowered because the protective film is formed on the portion to be polished. In order to prevent this, attempts have been made to optimize the amounts of etching agents and chelating agents used, but it is difficult to find conditions that satisfy the performance of both and it is easy to be affected by process conditions, resulting in reproducible results. There is a problem that can not be obtained. Also, 200 nm / min. In order to obtain the above high polishing rate, the protective film may be removed with a high polishing pressure of 20 kPa or more (Japanese Patent Application Laid-Open No. 2-212058).
No. 000-252242), the porous type low dielectric constant insulating film which will become the mainstream in the future has a problem in the film strength, so that if the substrate is overstressed, the insulating film is broken. In addition, if the polishing pressure is increased and mechanical polishing with a pad is performed, the pad surface during polishing becomes more susceptible to the influence, which makes it difficult to control the pad surface state by dressing, which is a major problem in process control. Becomes Further, there is a problem that the expensive pad is consumed quickly and the cost is increased.

By the way, polyoxo acids, especially heteropoly acids, are described in "Chemistry of Poly Acids" edited by The Chemical Society of Japan (August 1993,
It has strong acidity and oxidative action, as described in "Publishing Society of Japan", and it can be used for passivation and etching of metals.
It is described in Japanese Patent Publication No. An example of actually applying heteropolyacid as an etching agent for semiconductor surfaces (Applied)
SurfaceScience vol. 135, N
o. 1/4, pp65-70 (1998.10.8))
Attempts have also been made to use polyoxo acids or salts thereof as etching agents for polishing (JP 2000-11).
9639). Particularly in the latter, when only polyoxoacid or a salt thereof is used as an etching agent for polishing (first polishing composition) and when it further contains abrasive grains known as polishing agent (second polishing composition) ) Are described for two uses. In the case of the first polishing liquid composition, when the heteropoly acid is used alone as an etching agent for polishing a metal film, the heteropoly acid is soluble in water and acts as a liquid oxidizing agent. It cannot satisfy both of the dishing performance. That is, when the concentration of the heteropolyacid is increased in order to increase the polishing rate, etching also progresses at the same time and dishing occurs. On the other hand, when a basic substance such as ammonia is allowed to act on the above heteropolyacid to be used as a heteropolyacid salt, etching is suppressed, but at the same time, the polishing rate also decreases. Therefore, for the purpose of increasing the polishing rate, it has been proposed that a first polishing composition of this kind contains an abrasive to form a second polishing composition.
This is intended to perform mechanical polishing by using an abrasive, and a high polishing load is required to increase the polishing rate. Therefore, it does not meet the present object to obtain a high polishing rate with a low load.

[0007]

According to the present invention, a metal film on a semiconductor substrate can be polished at high speed even under a low load, and the etching property that causes dishing is controlled to a low level, and at the same time, scratches and erosion ( Figure 1
(Phenomenon in which the insulating film 2 around the metal film 4 in (D) is polished)
Polishing composition used for polishing a metal film formed on a semiconductor substrate capable of suppressing the occurrence of defects on the surface to be polished, and a method for polishing a metal film on a semiconductor substrate using the same, and a semiconductor It is an object to provide a method for manufacturing a substrate.

[0008]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, have found that a polishing composition containing a polyoxo acid, a water-soluble polymer and water It was found that a polishing composition containing an ionic surfactant enables both suppression of etching, which was conventionally difficult, and a high polishing rate under a low load, and is effective in polishing a metal film on a substrate. The present invention has been completed. That is, the present invention is as follows.

1. Polyoxo acids and / or salts thereof,
A metal polishing composition comprising a water-soluble polymer and water. 2. Further, it is characterized by containing a nonionic surfactant. The metal polishing composition as described above. 3. 1. The polyoxoacid and / or its salt is a heteropolyacid and / or its salt. Or 2. The metal polishing composition as described above. 4. The water-soluble polymer is at least one selected from the group consisting of polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, and cellulose derivatives. ~ 3. The polishing composition for metals according to any one of 1.

5. Nonionic surfactant HLB of 5
Is 12. ~ 4. The polishing composition for metals according to any one of 1. 6. 4. The nonionic surfactant is a polyoxyethylene ether of a saturated higher alcohol having 8 to 24 carbon atoms.
The metal polishing composition as described above. 7. The above 1. ~ 6. 13. A method for polishing a metal film on a semiconductor substrate, which comprises using the metal polishing composition according to any one of claims 1 to 5. 8. The above 1. ~ 6. A method for producing a semiconductor substrate, which comprises using the metal polishing composition according to any one of items 1 to 5.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention, particularly preferred embodiments thereof, will be specifically described below. The metal polishing composition of the present invention contains a polyoxoacid and / or a salt thereof, a water-soluble polymer and water, and may further contain a nonionic surfactant. The polishing composition of the present invention contains other components such as an inorganic abrasive grain, a resin abrasive grain, an oxidizer, and an acid in a range that does not impair the effects of the present invention as described below, or depending on the purpose. In addition, it is characterized in that the object of the present invention can be achieved by the above-mentioned three components or four components.

The polyoxoacid used in the present invention is M
Oxygen acids composed of elements such as o, V, W, Ti, Nb, and Ta are condensed, and isopoly acid and heteropoly acid correspond to this. Isopoly acid is a condensed oxygen acid consisting of a single element among the constituent elements of the polyoxo acid,
Examples thereof include polymolybdic acid, polyvanadic acid, polytungstic acid, polytitanic acid, polyniobic acid, and polytantalic acid. Among these, in the case of the present invention for the purpose of polishing a metal, polymolybdic acid, polyvanadate, and polytungstic acid are preferable from the viewpoint of the ability to etch (oxidize, dissolve) a metal.

The heteropoly acid is obtained by incorporating a hetero element into the isopoly acid as a central element, and its constitution is composed of a condensed coordination element, a central element and oxygen. Here, the condensation coordination element means a constituent element of the polyoxo acid, and among them, one containing at least one selected from the group consisting of Mo, W and V is mentioned as a preferable example, and Nb and Ta are also included. You may include elements, such as. The central element of the heteropolyacid is P, Si, A.
s, Ge, Ti, Ce, Mn, Ni, Te, I, Co,
It is one kind selected from the group consisting of Cr, Fe, Ga, B, V, Pt, Be and Zn, and the atomic ratio of the condensation coordination element and the central element (condensation coordination element / central element) is 2.5 to Twelve.

Specific examples of the above-mentioned heteropolyacid include:
Phosphomolybdic acid, silicomolybdic acid, phosphovanadomolybdic acid, silicovanadomolybdic acid, phosphotungstomolybdic acid, phosphotungstomolybdic acid, phosphovanadotungstomolybdic acid, cavanadotungstomolybdic acid, phosphovanadotungstic acid, cavanadotungsten Acid, phosphomolybdo niobate, boromolybdic acid,
Examples include but are not limited to borotungstomolybdic acid, borovanadomolybdic acid, borovanadotungstic acid, cobalt molybdic acid, cobalt vanadotungstic acid, phosphotungstic acid, silicotungstic acid, phosphovanadic acid, and silicovanadic acid. is not. Among the above polyoxo acids, a heteropoly acid is preferable from the viewpoint of sufficient acid strength sufficient for etching a metal for polishing purposes and oxidizing power, and is preferably phosphomolybdic acid, silicomolybdic acid, or lumbar having vanadium introduced therein. Examples thereof include nadomolybdic acid and cavanadomolybdic acid. The polyoxo acids may be used alone or as a mixture thereof. Further, for the purpose of adjusting the acidity of the obtained polishing composition and controlling the polishing performance, it is also possible to add a basic substance to these polyoxo acids and use them as a polyoxo acid salt. Examples of polyoxo acid salts include salts of the above polyoxo acids with metals, ammonium, and organic amines.

The content of the polyoxoacid and / or its salt in the polishing composition of the present invention is not particularly limited, but it is preferably used in the range of 0.1 to 30% by weight, more preferably 0. It is in the range of 0.5 to 15 wt%. When it is less than the above range, a sufficient polishing rate is difficult to develop, and even when it exceeds the above range, the polishing performance is not remarkably improved by increasing the amount.

The water-soluble polymer used in the present invention includes ethers such as polyethylene glycol, polypropylene glycol and polyethylene glycol alkyl ether; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; polyacrylic acid and polymethacryl. Polycarboxylic acids such as acids, polyacrylamides, polyamic acids, ammonium polyacrylates and salts thereof; polysaccharides such as methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, cellulose acetate, cellulose nitrate, cellulose sulfate, pectin, and others, gelatin, Examples thereof include starch and albumin, but are not limited thereto.
These water-soluble polymers may be contained as a thickening agent in the polishing composition (JP-A-8-302338) or as a surfactant in the polishing composition (JP-A-200).
0-252242), but the purpose of the present invention is different from them. That is, it was found that by using the water-soluble polymer in combination with the polyoxoacid, it is possible to suppress the progress of etching and control the occurrence of dishing while maintaining a high polishing rate even under a low load. It was. Among the above water-soluble polymers, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol and cellulose derivatives are preferable from the viewpoints of suppressing etching and polishing performance such as low load and high polishing rate, or dispersibility of particles produced.

Regarding the water-soluble polymer to be added,
Not only the type, but also its molecular weight has a great influence on the performance.
Generally, the larger the molecular weight of the water-soluble polymer to be added, the higher the effect of suppressing the etching tends to be, but there is also a trade-off with the dispersibility of particles and the polishing rate. The result can be various. The content of the water-soluble polymer used in the polishing composition of the present invention varies depending on the type and the type and amount of the polyoxo acid (salt thereof) used, but is preferably 0.01 to 50 w.
Used in the range of t%, more preferably 0.05 to 30
It is in the range of wt%. If it is less than the above range, it may be difficult to obtain a sufficient etching suppressing effect and it may be difficult to control the occurrence of dishing. If it exceeds the above range, handling may be difficult due to an increase in viscosity.

In the present invention, it is possible to further add a nonionic surfactant, which further improves the excellent properties of the particles produced, such as high dispersibility, low etching property and low load and high polishing rate. be able to. This effect is not observed when an anionic surfactant or a cationic surfactant, which is an ionic surfactant, is used, and the nonionic surfactant, especially HLB is 5-12.
It is remarkably observed when the one within the range is used.

Examples of such nonionic surfactants include "Introduction to New Surfactants by Takehiko Fujimoto, 1985, 1".
Issued on January 1, Sanyo Chemical Industry Co., Ltd. ”, page 92, second
The polyethylene glycol type and polyhydric alcohol type nonionic surfactants shown in Table 5.1 can be applied. The polyethylene glycol-type nonionic surfactant is one in which ethylene oxide is added to various hydrophobic groups to introduce a hydrophilic group, and higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene oxide. Adduct, polyhydric alcohol fatty acid ester ethylene oxide adduct, higher alkylamine ethylene oxide adduct, fatty acid amide ethylene oxide adduct,
Examples thereof include ethylene oxide adducts of fats and oils, polypropylene glycol ethylene oxide adducts, and the like. On the other hand, the polyhydric alcohol type nonionic surfactant is a hydrophilic polyhydric alcohol in which a hydrophobic fatty acid is bound via an ester or amide group, and is a fatty acid ester of glycerol or a fatty acid ester of pentaerythritol. , Fatty acid esters of sorbitol and sorbitan,
Examples thereof include fatty acid esters of sucrose and fatty acid amides of alkanolamines.

Among these nonionic surfactants, those used in the present invention preferably have an HLB of 5 to 5.
Although it is in the range of 12, if this value is lower than 5, the hydrophobicity of the particles tends to be strong, and sedimentation or layer separation of the particles may occur due to poor dispersibility. On the other hand, when it is more than 12, the hydrophilicity is likely to be high, and the formation of the child may be insufficient, and the effect of suppressing etching may be difficult to be exhibited. The nonionic surfactant added to the polishing composition in the present invention is preferably a polyoxyethylene ether of a higher alcohol having 8 to 24 carbon atoms or a polyphenol of an alkylphenol, which is classified as the polyethylene glycol type surfactant. Examples thereof include oxyethylene ether and polyoxyethylene ether of polypropylene glycol (Pluronic type). Among them, polyoxyethylene ether of higher alcohol having 8 to 24 carbon atoms is particularly preferable. The higher alcohol polyoxyethylene ether having 8 to 24 carbon atoms includes an unsaturated type having a carbon-carbon double bond in the molecule such as an oleyl group and a saturated type having no carbon-carbon double bond at all. However, a saturated higher alcohol polyoxyethylene ether is preferable because the saturated group is less likely to be deteriorated by oxidation and does not deteriorate in performance over time. Examples thereof include polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene 2
-Ethylhexyl ether, polyoxyethylene tridecyl ether, polyoxyethylene isostearyl ether, polyoxyethylene synthetic alcohol ether (carbon number 12 to 15 in synthetic alcohol) and the like can be mentioned.

Although only one kind of these nonionic surfactants may be added, the excellent performance of the polishing composition of the present invention, that is, generation, can be obtained by using two or more kinds of HLB having different HLBs in combination. It is possible to further improve the high dispersibility and low etching property of the polishing particles, and the high speed polishing property under a low load. The content of the nonionic surfactant used in the polishing composition of the present invention varies depending on the type and the type and amount of the polyoxoacid (salt thereof) or the water-soluble polymer used, but is preferably 0 to 50 wt. %, And more preferably 0 to 30 wt%. If it exceeds the above range, handling such as increase in viscosity may be difficult.

The polishing composition of the present invention generally uses water as a medium. The polyoxo acid (salt thereof), the water-soluble polymer, and the nonionic surfactant, which is optionally further added, are usually dissolved or dispersed by stirring, but using a homogenizer, ultrasonic waves, a wet medium mill, or the like. A method of sufficiently dispersing is preferably used. The polishing composition thus prepared is preferably a composition (fine particles) which exists in a highly dispersed state in water as a complex (fine particles) due to the interaction between the polyoxo acid (salt thereof) and the water-soluble polymer. When a nonionic surfactant is further contained, it is also incorporated into the complex by the interaction with the polyoxo acid (salt thereof).
The composite here is basically capable of measuring the particle size by a wet particle size analyzer as described later and observing the above structure by a transmission electron microscope, and the number average particle measured by the wet particle size analyzer. Those having a diameter of about 10 nm to 1 μm are preferable. However, those having a number average particle diameter of about 10 nm or less and existing in a fine and highly dispersed state such that the particle size is difficult to measure are also included in the scope of the present invention.

In the polishing composition of the present invention, the details of the polishing mechanism are not clear, but a polyoxo acid (salt thereof) is used.
And the fine particles formed by the interaction of the water-soluble polymer act as abrasive particles expressing a chemical polishing action, while maintaining low etching property and controlling the occurrence of dishing,
It is considered that a high polishing rate can be exhibited even with a low load. Therefore, the abrasive particles are essentially different in character from the abrasive particles conventionally used for the purpose of mechanical polishing, and are problems caused by conventional mechanical polishing. Damage to the base substrate due to the load is eliminated.

As described above, the polishing composition of the present invention can basically carry out the desired polishing without containing the abrasive grains which are usually used for the purpose of mechanical polishing, but surface defects such as scratches. It is also possible to use abrasive grains for the purpose of further increasing the polishing rate within the range that does not occur. Examples of the abrasive grains used at that time include inorganic particles such as alumina, silica, ceria, zirconia, titania, and magnesium oxide, organic polymers, amorphous carbon, and organic particles such as carbon black. Colloidal alumina and colloidal silica.

Since the polishing composition of the present invention has an extremely low etching property of a metal film which causes dishing, it is usually unnecessary to use a protective film-forming agent together, but within a range that does not substantially lower the polishing rate. Then, if necessary, a compound that forms a chelate or a complex with the metal film may be added to further suppress the etching property. Particularly when the metal is copper or a copper alloy containing copper as a main component, a method of adding benzotriazole or quinaldic acid as a chelating agent is effective. In addition to these, examples of the anticorrosive agent include benzotriazole derivatives such as tolyltriazole and benzotriazolecarboxylic acid, cystine, haloacetic acid, glucose, and dodecyl mercaptan.
The addition amount of these anticorrosives is preferably 100 ppm or less, more preferably 50 ppm or less, which is an extremely small amount as compared with the amount used in conventional abrasives. On the other hand, if the amount of addition is large, the polishing rate may decrease and the desired polishing performance may not be obtained.

The polishing composition of the present invention may further contain a known oxidizing agent within the range of not causing excessive etching for the purpose of improving the polishing rate of the metal film. As the oxidizing agent to be contained, known oxidizing agents, for example, peroxides such as hydrogen peroxide, perchloric acid, perchlorates, periodate,
Examples thereof include periodate, persulfate, persulfate, nitrate and the like. The polishing composition of the present invention may contain an acid as required, and the polishing performance of the metal film can be controlled by the type of acid used and the pH of the resulting slurry. Examples of the acid to be contained include known inorganic acids such as sulfuric acid, phosphoric acid and nitric acid, and known organic acids such as oxalic acid, citric acid, malic acid and acetic acid. Water-soluble alcohols such as methanol, ethanol, n-propanol, iso-propanol, ethylene glycol, and glycerin can be added to the polishing composition of the present invention, if necessary.

The polishing composition of the present invention thus prepared is applied to polishing and planarizing a metal film formed on a semiconductor substrate. The metal film on the semiconductor substrate to be polished is a known wiring, plug, contact metal layer,
Examples of the metal film for the barrier metal layer include metal films selected from the group consisting of aluminum, copper, tungsten, titanium, tantalum, aluminum alloys, copper alloys, titanium nitride, tantalum nitride, and the like. In particular, it is recommended to apply to a metal film made of copper and a copper alloy, which has a low surface hardness and is susceptible to defects such as scratches and dicing.

As shown in FIG. 1C, a semiconductor substrate obtained by embedding a metal film 4 for wiring is
As shown in FIG. 1 (D), the excess metal film other than the groove or opening is polished by using a polishing composition containing a polyoxo acid (salt thereof) and a water-soluble polymer. Remove and flatten. In the method for producing a semiconductor substrate of the present invention, a metal film on a semiconductor substrate such as a silicon substrate is polished with a metal polishing composition containing a polyoxoacid (salt thereof) and a water-soluble polymer. It is characterized by comprising a process. Hereinafter, a method for manufacturing a semiconductor substrate will be described.

First, as shown in FIG. 1A, after forming an insulating film 2 on a semiconductor substrate 1 such as a silicon substrate, a groove for metal wiring or a connection is formed in the insulating film 2 by photolithography and etching. An opening for wiring is formed.
Next, as shown in FIG. 1B, a barrier metal layer 3 made of titanium nitride (TiN), tantalum nitride (TaN), or the like is formed in the groove or opening formed in the insulating film 2 by a method such as sputtering or CVD. To do. Next in FIG.
As shown in (C), the metal film 4 for wiring is embedded so that the thickness is equal to or higher than the height of the groove or opening formed in the insulating film 2. Next, as shown in FIG. 1D, a method of polishing an excess metal film other than the groove or opening with a metal polishing composition characterized by containing a polyoxoacid and a water-soluble polymer is used. remove. Furthermore, by repeating the above method a required number of times, a semiconductor substrate having a multilayer wiring structure as an electronic component can be obtained. It should be noted that the polishing composition for metal or the method for planarizing the metal film described above may be applied to the polishing of the metal film on the semiconductor substrate in the production of the semiconductor substrate as described above.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto.
The characteristics and polishing performance of the polishing composition were evaluated by the following methods. <Measurement of particle size> (1) Fine particles (less than 5 μm): wet particle size analyzer manufactured by Nikkiso Co., Ltd. under the trade name “Microtrac UPA-9230”
Was measured using. (2) Coarse (5 μm or more) particles: Wet particle size analyzer It was measured using Horiba Seisakusho's trade name “LA-700”. The average particle diameter in the present invention means the particle diameter by number average.

<Measurement of Polishing Rate> The change in each film thickness before and after polishing was calculated by dividing by the polishing time. The polishing conditions were such that the polishing pressure was 5 kPa and the relative speed between the substrate and the polishing pad was 40 m / min. "IC1400" for polishing pad
(Trade name, manufactured by Rodel Nitta Co., Ltd.), a copper film (thickness: 1 μm was added while the metal polishing composition was dropped onto the polishing pad.
m) attached silicon wafer was polished.

<Evaluation of Surface Defects (Scratches)> After cleaning and drying the silicon wafer polished in the above <Measurement of polishing rate>, a spotlight was applied to the surface of the semiconductor wafer in a dark room to visually determine the presence or absence of scratches. .

<Evaluation of Dispersibility of Polishing Composition> The dispersion state of each polishing composition after standing for 1 day at room temperature was visually evaluated as follows. ○: No sediment △: Small sediment ×: Large sediment

<Evaluation of Dishing Property by Measuring Etching Rate> By evaluating the wet etching property, which is a cause of occurrence of dishing, an alternative evaluation of the dishing property was made. That is, since the dishing is caused by the erosion of the metal film due to the excessive chemical action (wet etching) of the polishing composition, the etching rate of the polishing composition, which is the main cause of the dishing, is The evaluation here results in the evaluation of the dishing characteristics.

Specifically, a silicon wafer with a copper film (thickness: 1 μm) is immersed in a polishing composition for a certain period of time and shaken,
The change in film thickness before and after the immersion was measured, and the etching rate was obtained by dividing the change in the immersion time, and the dishing characteristics were evaluated according to the following criteria (⊚ to ×). The slower the etching rate, the weaker the wet etching property and the less likely dishing occurs. ⊚: Etching rate less than 1 nm / min ○: Etching rate 1 to 10 nm / min Δ: Etching rate 10 to 50 nm / min ×: Etching rate over 50 nm / min

[0036]

EXAMPLE 1 Phosphovanadomolybdic acid as a polyoxo acid: 6 g of PVMo (trade name "PVM-1-11" manufactured by Japan Inorganic Chemical Industry Co., Ltd.) was dissolved in 154 g of water, and a water-soluble polymer was added thereto while stirring with a homogenizer. An aqueous solution prepared by dissolving 6 g of polyvinylpyrrolidone K30: PVP (average molecular weight 40,000, manufactured by Wako Pure Chemical Industries, Ltd.) in 34 g of pure water was added to obtain a metal polishing composition. "UP" of this composition
The average particle diameter measured by "A-9230" was about 700 nm. The evaluation results are shown in Table 1. The composition showed no discoloration or sedimentation of particles even after being left at room temperature for 1 month.
It showed good stability and dispersibility.

[0037]

EXAMPLE 2 6 g of PVMo as a polyoxo acid was added to water 11
An aqueous solution prepared by dissolving 12 g of PVP as a water-soluble polymer in 68 g of pure water as a water-soluble polymer was added to 4 g of the solution under stirring with a homogenizer to obtain a metal polishing composition. This composition became a uniform solution visually, and the average particle size measured by "UPA-9230" was about 10 nm. The evaluation results are shown in Table 1. The composition showed no discoloration or settling of particles even after being left at room temperature for one month, and showed good stability and dispersibility.

[0038]

Example 3 6 g of PVMo as a polyoxo acid was added to water 62.
g and dissolve it in a homogenizer while stirring to give polyethylene glycol 4000: PEG as a water-soluble polymer.
-1 (average molecular weight 3000, Wako Pure Chemical Industries, Ltd.) 40 g
An aqueous solution in which 92 g of pure water was dissolved was added to obtain a metal polishing composition. This composition became a uniform solution, and the particle size could not be measured. The evaluation results are shown in Table 1.

[0039]

Example 4 6 g of PVMo as a polyoxo acid was added to water 94.
g and dissolve it in a homogenizer with stirring to give polyethylene glycol 20000: PE as a water-soluble polymer.
G-2 (average molecular weight 20000, Wako Pure Chemical Industries, Ltd.) 3
An aqueous solution prepared by dissolving 0 g in 70 g of pure water was added to obtain a metal polishing composition. This composition became a uniform solution, and the particle size could not be measured. The evaluation results are shown in Table 1.

[0040]

Example 5 9 g of PVMo as a polyoxo acid was added to 12 parts of water.
It was dissolved in 3 g and stirred with a homogenizer, to which was added an aqueous solution in which 15 g of PEG-1 as a water-soluble polymer was dissolved in 35 g of pure water, and then polyoxyethylene lauryl ether was added as a nonionic surfactant. : SF-1
(Product name "BLAUNON EL-1503P", HL
B = 8.3, manufactured by Aoki Yushi Kogyo Co., Ltd.) was added to obtain a metal polishing composition. This composition of "UPA
The average particle size measured by "-9230" was about 70 nm. The evaluation results are shown in Table 1. The composition showed no discoloration or settling of particles even after being left at room temperature for one month, and showed good stability and dispersibility.

[0041]

Example 6 Benzotriazole (BTA) was added to the polishing composition obtained in Example 5 so that the concentration was 50 ppm.
Was added to obtain a metal polishing composition containing an anticorrosive agent. The average particle size of this composition measured by "UPA-9230" was about 70 nm, which was the same as the polishing composition obtained in Example 5. The evaluation results are shown in Table 1. In addition,
The composition showed no discoloration or sedimentation of particles even after standing at room temperature for one month, and showed good stability and dispersibility.

[0042]

Example 7 Instead of SF-1 as the nonionic surfactant, polyoxyethylene oleyl ether: SF-
2 (Brand name "BLAUNON EN-905", HLB
= 8.9, manufactured by Aoki Yushi Kogyo Co., Ltd.)
A polishing composition for metal was obtained in exactly the same manner as. The average particle size of this composition measured by "UPA-9230" is about 15
It was 0 nm. The evaluation results are shown in Table 1. Discoloration and sedimentation of particles were confirmed after the composition was left at room temperature for about 2 weeks.

[0043]

Example 8 6 g of PVMo as a polyoxo acid was added to 16 parts of water.
It was dissolved in 8 g and stirred with a homogenizer, an aqueous solution prepared by dissolving 6 g of PEG-1 as a water-soluble polymer in 14 g of pure water was added to this, and then polyoxyethylene lauryl ether as a nonionic surfactant was added thereto. : SF-3
(Brand name "BLAUNON EL-1502.2", H
LB = 6.3, manufactured by Aoki Yushi Kogyo Co., Ltd.) was added to obtain a metal polishing composition. This composition of "UPA
The average particle size measured by "-9230" was about 120 nm. The evaluation results are shown in Table 1. The composition showed no discoloration or settling of particles even after being left at room temperature for one month, and showed good stability and dispersibility.

[0044]

Example 9 9 g of PVMo as a polyoxo acid was added to water 11
6 g of ethanol and 6 g of ethanol, and with stirring with a homogenizer, an aqueous solution of 9 g of PVP as a water-soluble polymer in 51 g of pure water was added thereto, and then SF-1 as a nonionic surfactant was added thereto. A polishing composition for metals was obtained by adding 9 g. UPA-9 of this composition
The average particle diameter measured by 230 was about 300 nm.
The evaluation results are shown in Table 1. The composition showed no discoloration or settling of particles even after being left at room temperature for one month, and showed good stability and dispersibility.

[0045]

Example 10 12 g of PVMo as a polyoxo acid was dissolved in 178 g of water and stirred with a homogenizer, and a polyoxyethylene cetyl ether: SF-4 (trade name “BLAUNON CH-as a nonionic surfactant was added thereto.
305 ", HLB = 9.4, manufactured by Aoki Yushi Kogyo Co., Ltd.), and then hydroxypropyl cellulose as a water-soluble polymer: HPC (150 to 400 mPa · s,
A polishing composition for metal was obtained by adding an aqueous solution prepared by dissolving 0.4 g of Wako Pure Chemical Industries, Ltd. in 3.6 g of pure water.
The average particle size of this composition measured by "UPA-9230" was about 320 nm. The evaluation results are shown in Table 1. The composition did not show discoloration even after being left at room temperature for 1 month, but it was confirmed that particles settled.

[0046]

Example 11 12 g of PVMo as a polyoxo acid was dissolved in 176 g of water, and a solution of 6 g of SF-4 as a nonionic surfactant in 2 g of ethanol was added to the solution under stirring with a homogenizer. Polyoxyethylene synthetic alcohol ether: SF-5 (trade name "BLAUNON OX-2
0 ", HLB = 5.7, manufactured by Aoki Yushi Kogyo Co., Ltd.) was added. Next, 0.2 g of HPC as a water-soluble polymer
Was added to an aqueous solution of 1.8 g of pure water to obtain a metal polishing composition. This composition of "UPA-92
The average particle size measured by "30" was about 150 nm.
The evaluation results are shown in Table 1. The composition did not show discoloration even after being left at room temperature for 1 month, but it was confirmed that particles settled.

[0047]

Example 12 6 g of PVMo as a polyoxo acid was added to 1 part of water.
After being dissolved in 69 g and stirred with a homogenizer, an aqueous solution prepared by dissolving 6 g of PEG-1 as a water-soluble polymer in 6 g of pure water was added thereto, and then PV was added as a water-soluble polymer.
An aqueous solution prepared by dissolving 1 g of P in 6 g of pure water was added. Next, 6 g of SF-1 as a nonionic surfactant was added thereto to obtain a metal polishing composition. The average particle size of this composition measured by "UPA-9230" is about 70.
was nm. The evaluation results are shown in Table 1. The composition showed no discoloration or settling of particles even after being left at room temperature for one month, and showed good stability and dispersibility.

The polishing composition containing the fine particles thus obtained in the above examples was dropped on a grid with a carbon support film and naturally dried to obtain a sample for microscopy, and a transmission electron microscope (trade name " HITACHI HF-200
When the particle structure was observed with an accelerating voltage of 200 KV), the presence of particles having a form in which polyoxoacid was incorporated in a nonionic surfactant was confirmed. Although the particle size depends on the polishing composition, a particle size of about 20 to 50 nm was observed, and a structure in which it was thought that they were further aggregated was observed.

[0049]

Comparative Example 1 A metal polishing composition was prepared by dissolving 12 g of phosphovanadomolybdic acid: PVMo as a polyoxo acid in 188 g of water and using no water-soluble polymer. This composition was in a uniform solution state, and the particle size could not be measured. The evaluation results are shown in Table 2.

[0050]

Comparative Example 2 12 g of ammonium phosphomolybdate: NPMo ((NH ₄ ) ₃ [PMo ₁₂ O ₄₀ ] manufactured by Nippon Inorganic Chemical Co., Ltd.) as a polyoxo acid salt was well pulverized, then added to 88 g of water, and dispersed by a homogenizer. It was Next, 100 g of colloidal alumina (average particle size 130 nm, manufactured by Catalysis Co., Ltd.) was added to this so that the concentration of the abrasive grains in the composition was 6%, and a dispersion treatment was further performed with a homogenizer to obtain a metal containing alumina particles as abrasive grains. A polishing composition for use was obtained. The average particle size of this composition measured by "UPA-9230" was about 160 nm. It should be noted that, when this composition was left at room temperature for several hours, sedimentation of abrasive grains was observed.
The evaluation results are shown in Table 2.

[0051]

[Comparative Example 3] A solution obtained by dissolving 6 g of citric acid in 62 g of water and dissolving it, and dissolving 0.4 g of BTA in 3 g of ethanol was added, and the concentration of abrasive grains in the composition was 6%.
100 g of colloidal alumina (same as above) was added to the mixture so that hydrogen peroxide solution (reagent grade, 30% aqueous solution) was added.
8 g was added to prepare a metal polishing composition. The average particle size of this composition measured by "UPA-9230" is about 15
It was 0 nm. It should be noted that, when this composition was left at room temperature for several hours, sedimentation of abrasive grains was observed. The evaluation results are shown in Table 2.

[0052]

Comparative Example 4 6 g of citric acid and P as a water-soluble polymer
6 g of VP was added to 60 g of water to dissolve it, and 100 g of colloidal alumina (same as above) was added thereto so that the concentration of the abrasive grains in the composition was 6%, and then hydrogen peroxide solution (special grade reagent, 3%
28% of 0% aqueous solution) was added to prepare a metal polishing composition. The average particle size of this composition measured by "UPA-9230" was about 150 nm. It should be noted that, when this composition was left at room temperature for several hours, sedimentation of abrasive grains was observed.
The evaluation results are shown in Table 2.

From the results shown in Tables 1 and 2, the polishing composition of the present invention shows that even under a low load of 5 kPa,
400 nm / min. For copper film. It can be seen that the polishing rate is extremely high as described above. The etching property is 10 nm / min. Without adding an anticorrosive agent. It is suppressed to a low level below, and it can be seen that it is effective in suppressing dishing. Further, the addition of BTA can further suppress the etching property, but the addition amount is as small as about 50 ppm, and the polishing rate is not significantly reduced. It can be seen that scratches are not seen at all as compared with the conventional system in which abrasive grains are added, and surface defects are not generated and the polishing performance is excellent. On the other hand, as shown in the comparative example, the polishing liquid containing only heteropolyacid has too high an etching property to obtain the desired performance.
Further, even when using the heteropoly acid in the form of ammonium salt, since the polishing rate for the copper film is extremely reduced, alumina abrasive grains were added to this for the purpose of mechanical polishing. It can be seen that a high polishing rate cannot be obtained. In addition, the etching property is 10
nm / min. It can be seen that when BTA, which is only suppressed within the range, is added as an anticorrosive agent, the polishing rate is also lowered at the same time, and the characteristics obtained in the present invention cannot be obtained even if abrasive grains are added. Further, in the present invention, the addition of a water-soluble polymer to the heteropoly acid achieves the suppression of the etching property and the low load high polishing rate, but as can be seen from the comparative examples, hydrogen peroxide is used as the oxidant. Even if a water-soluble polymer is added to the above general system, the effect of suppressing the etching property is not seen, and it can be seen that this effect is peculiar to the present invention.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

According to the present invention, it has become possible to achieve both suppression of etching and dishing and high-speed polishing of a metal film such as a copper film under low load conditions, which were difficult in the past. The present invention has found a material having extremely useful performance for polishing a metal film on a semiconductor substrate, and has a great industrial utility value.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of forming a metal wiring using a CMP technique, and (A), (B), (C), and (D) are schematic cross-sectional views showing the respective steps. .

[Explanation of symbols]

1 Semiconductor substrate 2 insulating film 3 Barrier metal layer 4 metal film

Claims (8)

[Claims] 1. A polishing composition for metals comprising a polyoxo acid and / or a salt thereof, a water-soluble polymer and water. 2. The polishing composition for metals according to claim 1, further comprising a nonionic surfactant. 3. A polyoxoacid and / or a salt thereof,
The metal polishing composition according to claim 1 or 2, which is a heteropoly acid and / or a salt thereof. 4. The metal polishing according to any one of claims 1 to 3, wherein the water-soluble polymer is at least one selected from the group consisting of polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol and cellulose derivatives. Composition. 5. A nonionic surfactant having an HLB of 5 to 1
The polishing composition for metals according to claim 2, wherein the polishing composition is 2. 6. The nonionic surfactant has 8 to 24 carbon atoms.
6. The polishing composition for metals according to claim 5, which is polyoxyethylene ether of saturated higher alcohol. 7. A method for polishing a metal film on a semiconductor substrate, which comprises using the metal polishing composition according to any one of claims 1 to 6. 8. A method for producing a semiconductor substrate, which comprises using the metal polishing composition according to claim 1.