JP2005116778A - Water system dispersant for metal polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water system dispersant for metal polishing which enables a metallic film to be polished rapidly even under low loading conditions and restrains generation of defect of a polishing surface such as scratch and dishing in a process for flattening a metallic film on a semiconductor substrate, a flattening method of the metallic film on the semiconductor substrate using it, and a manufacturing method of the semiconductor substrate. <P>SOLUTION: The water system dispersant comprises a complex particle formed of a polyoxo acid, nonionic surfactant and anionic surfactant. The flattening method of the metallic film on the semiconductor substrate using it, and a manufacturing method of the semiconductor substrate, are also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aqueous dispersion for metal polishing 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 manufacturing a semiconductor substrate.

Due to the rapid development of LSI technology, integrated circuits are increasingly miniaturized and multi-layered. Multi-layer wiring in integrated circuits is a factor that causes extremely large irregularities on the surface of the semiconductor. This, combined with the miniaturization of integrated circuits, leads to disconnection, lower capacitance, and electromigration, resulting in reduced yield and reliability. This is the cause of the problem.
For this reason, various processing techniques for flattening metal wirings and interlayer insulating films in a multilayer wiring board have been developed so far, one of which is a CMP (Chemical Mechanical Polishing) technique. The CMP technique is a technique required for planarizing an interlayer insulating film, forming an embedded wiring, forming a plug, and the like in semiconductor manufacturing.
CMP is performed by rotating each of the carrier and the polishing pad while pressing a flat wafer made of a normal semiconductor material mounted on the carrier against the wet polishing pad with a constant pressure. At this time, the convex portions 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 metal films on semiconductor substrates. As shown in Non-Patent Document 1, in metal CMP, the surface of the metal is oxidized and passivated by an oxidizing agent in the polishing composition, and the metal is slightly corroded by acidifying the pH, etc. ( Polishing is performed with a polishing pad and abrasive grains under conditions of etching. For example, as a polishing composition for a metal film such as aluminum formed on a semiconductor substrate, a polishing composition in which aluminum oxide is dispersed in an aqueous nitric acid solution having a pH of 3 or less (Patent Document 1), aluminum oxide or silicon oxide is sulfuric acid, There exists polishing composition (patent document 2) formed by mixing with acidic aqueous solutions, such as nitric acid and acetic acid. Further, a polishing composition comprising abrasive grains such as aluminum oxide or silicon oxide and an oxidizing agent such as hydrogen peroxide, such as a polishing composition in which aluminum oxide is dispersed in hydrogen peroxide and an aqueous phosphoric acid solution (Patent Document 3). 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 defects such as micro scratches and orange peels may be generated on the surface of the metal film or insulating film. there were. On the other hand, when abrasive grains such as γ-type, amorphous alumina, or silicon oxide are used, the occurrence of defects such as micro scratches and orange peel on the surface of the metal film or insulating film can be suppressed. There was a problem that a sufficient polishing rate could not be obtained.

In addition, when hydrogen peroxide as a liquid oxidizing agent is used as described above, or when a metal etchant such as ammonium persulfate is used (Patent Document 4), dishing ( There has been a problem in practical use, such as a phenomenon in which the central portion of the metal film 4 in FIG. 1D is excessively polished from the peripheral portion) and defects such as pits and voids.
In order to improve this, a method of adding a chemical reagent (such as an anticorrosive or a chelating agent) that forms a protective film on the surface of the metal film in the polishing composition has also been proposed (Patent Documents 5 and 6). However, when such a chelating agent is used, etching is surely suppressed and the occurrence of dishing and the like can be prevented. However, since a protective film is also formed on the portion to be polished, the polishing rate is extremely reduced. Occurs. Attempts have been made to optimize the use of etching agents and chelating agents to prevent this, but it is difficult to find conditions that satisfy the performance of both, and the results are reproducible because they are also susceptible to process conditions. There is a problem that cannot be obtained. Further, in order to obtain a high polishing rate of 200 nm / min or more, the protective film is also removed at a high polishing pressure of 200 g / cm ² or more (Patent Document 7), but it is predicted that it will become mainstream in the future. In the case of the porous type low dielectric constant insulating film, there is a problem in the film strength. Therefore, when an excessive stress is applied to the substrate, the insulating film is destroyed. In addition, if the polishing pressure is increased and mechanical polishing with the pad is performed, it becomes more susceptible to the influence of the pad surface at the time of polishing. It becomes. Furthermore, there is a problem that expensive pads are consumed quickly and cost is increased.

  By the way, polyoxoacids, especially heteropolyacids, have strong acidity and oxidizing action as described in Non-Patent Document 2, and it is disclosed in Patent Document 8 that they are used for metal passivation treatment and etching. Has been described. Actually, an example in which a heteropolyacid is applied as an etching agent on a semiconductor surface (Non-patent Document 3), and an attempt to use a polyoxoacid or a salt thereof as an etching etchant has been made (Patent Document 9). In particular, in the latter case, when only polyoxo acid or a salt thereof is used as a polishing etchant (first polishing composition) and when a known abrasive is further added as an abrasive (second polishing composition). Two usages are described. In the case of the first polishing composition, when the heteropolyacid is used alone as an etching agent for polishing a metal film, the heteropolyacid is soluble in water and thus acts as a liquid oxidizing agent. Both performances cannot be satisfied. That is, when the concentration of the heteropolyacid is increased in order to increase the polishing rate, etching progresses simultaneously and dishing occurs. On the other hand, when a basic substance such as ammonia is allowed to act on the heteropolyacid to be used as a heteropolyacid salt, etching is suppressed, but at the same time, the polishing rate is reduced. Therefore, for the purpose of increasing the polishing rate, it has been proposed that this type of first polishing composition contains an abrasive to form a second polishing composition, which is mechanically polished by using the abrasive. In order to increase the polishing rate, a high polishing load is required. Therefore, it does not meet the purpose of obtaining a high polishing rate with a low load.

US Pat. No. 4,702,792 US Pat. No. 4,944,836 US Pat. No. 5,209,816 Japanese Patent Laid-Open No. 06-313164 Japanese Patent Laid-Open No. 08-083780 JP-A-11-195628 JP 2000-252242 A Japanese Translation of National Publication No. 09-505111 JP 2000-119639 A Toshiro Tohi et al., “Semiconductor planarization CMP technology”, first edition, published by Industrial Research Council, July 15, 1998, page 235 Edited by Chemical Society of Japan, “Chemistry of Polyacids”, First Edition, Society Publishing Center, August 25, 1993, 86-87, 112-123 A. Rothschild, C.I. Debemme-Chouvy, A.M. Etcheberry, “Studyoftheinteractionatrepotentialbetweensilicotungstichiopolystyrenesolution and GaAs surface”, Applied Surface Science, Oct. 8, 1998, vol. 135, no. 1/4, pp65-70

  In the present invention, a metal film on a semiconductor substrate can be polished at a high speed even under a low load, and the etching property causing dishing is controlled to a low level, and at the same time, scratch and erosion (the metal film 4 in FIG. 1D) are controlled. 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, such as a phenomenon in which the insulating film 2 around the substrate is polished), and the like An object of the present invention is to provide a method for polishing a metal film on a semiconductor substrate and a method for manufacturing a semiconductor substrate.

As a result of diligent studies to solve the above problems, the present inventors have found that an aqueous dispersion for metal polishing containing composite particles formed from a polyoxoacid, a nonionic surfactant, and an anionic surfactant However, it has been found that the present invention makes it possible to achieve both the suppression of etching and dishing, which has been difficult in the past, and the high polishing rate under a low load, and is effective in polishing a metal film on a substrate. That is, the present invention is as follows.
1) An aqueous dispersion for polishing metal comprising composite particles formed from a polyoxoacid, a nonionic surfactant, and an anionic surfactant.
2) The metal-polishing aqueous dispersion according to 1), wherein the polyoxoacid is a heteropolyacid.
3) An aqueous dispersion for metal polishing according to the invention of 1) or 2), wherein the anionic surfactant is in acid form.
4) The aqueous dispersion for metal polishing according to any one of 1) to 3), wherein two or more kinds of nonionic surfactants having different HLBs are used in combination as the nonionic surfactant.
5) The water-based dispersion for metal polishing according to any one of 1) to 4), which comprises a water-soluble polymer compound and / or a polyhydric alcohol compound.
6) An aqueous dispersion for metal polishing according to any one of 1) to 5), which comprises an organic compound having both a nitrogen atom and a carboxyl group in the molecule.
7) The aqueous dispersion for metal polishing according to any one of 1) to 6), which is substantially free of abrasive grains.
8) A method for polishing a metal film on a semiconductor substrate, comprising using the metal polishing aqueous dispersion according to any one of 1) to 7).
9) A method for producing a semiconductor substrate, comprising using the metal polishing aqueous dispersion according to any one of 1) to 7).

  According to the aqueous dispersion for metal polishing of the present invention, it is possible to polish a metal film such as a copper film at high speed even under a low load while suppressing etching and dishing, which has been difficult with the prior art. The present invention has found a material having extremely useful performance in polishing a metal film on a semiconductor substrate, and has a great industrial utility value.

The present invention will be specifically described below.
In the present invention, low load means 150 g / cm ² or less, and high speed polishing means a polishing rate of 300 nm / min or more.
The metal polishing aqueous dispersion of the present invention comprises composite particles formed from a polyoxo acid, a nonionic surfactant, and an anionic surfactant. The aqueous dispersion for metal polishing of the present invention contains other components such as additives that are usually used within the range not inhibiting the effects of the present invention as described later, or depending on the purpose, but basically the above-mentioned It is a feature that the object of the present invention can be achieved with only three components. That is, the polishing composition of the present invention is characterized by exhibiting excellent polishing performance even when substantially free of abrasive grains. Here, “substantially free of abrasive grains” means that the ratio of the mass of abrasive grains in the total mass of the polishing composition is 0 to less than 1% (therefore, the abrasive grains are an optional component). Say.

The polyoxo acid used in the present invention is a condensate of an oxygen acid composed of elements such as Mo, V, W, Ti, Nb, Ta, etc., and an isopoly acid and a heteropoly acid correspond to this. The isopolyacid is a condensed oxygen acid composed of a single element among the constituent elements of the polyoxoacid, and examples thereof include polymolybdic acid, polyvanadic acid, polytungstic acid, polytitanic acid, polyniobic acid, and polytantalic acid. Of these, polymolybdic acid, polyvanadic acid, and polytungstic acid are preferable from the viewpoint of the ability to etch (oxidize and dissolve) metal in the present invention for the purpose of metal polishing.
The heteropolyacid is obtained by incorporating a heteroelement as a central element into the isopolyacid, and its structure is composed of a condensed coordination element, a central element and oxygen. Here, the condensed coordination element means a constituent element of the polyoxoacid, and among these, those containing at least one selected from the group consisting of Mo, W and V can be mentioned as preferred examples, and other Nb, Ta Or the like. The central element of the heteropolyacid is selected from the group consisting of P, Si, As, Ge, Ti, Ce, Mn, Ni, Te, I, Co, Cr, Fe, Ga, B, V, Pt, Be, and Zn. The atomic ratio of the condensed coordination element to the central element (condensed coordination element / central element) is 2.5-12.

  Specific examples of the heteropolyacids described above include phosphomolybdic acid, silicomolybdic acid, phosphovanadomolybdic acid, cayvanadomolybdic acid, phosphotungstomolybdic acid, cytongustomolybdic acid, phosphovanadotungstomolybdic acid, and cyvanadotungstomolybdenum. Acid, phosphovanadotungstic acid, cayvanadotungstic acid, phosphomolybdniobic acid, boromolybdic acid, borotungstomolybdic acid, borovanadomolybdic acid, borovanadotungstic acid, cobaltmolybdic acid, cobaltvanadotungstic acid, phosphotungsten Examples thereof include, but are not limited to, acid, silicotungstic acid, phosphovanadic acid, and silicovanadic acid. Among the polyoxoacids, heteropolyacids are preferable from the viewpoint of sufficient acid strength and oxidizing power sufficient for etching a metal for polishing purposes, and preferably phosphomolybdic acid, silicomolybdic acid, and phosphorous containing vanadium introduced therein. Examples thereof include nadmolybdic acid and caivanadomolybdic acid. The polyoxo acids may be used alone or in combination.

For the purpose of adjusting the acidity of the resulting metal polishing aqueous dispersion and controlling the polishing performance, a basic substance may be added to these polyoxoacids, and some or all of the polyoxoacids may be used as polyoxoacid salts. Is possible. Examples of the polyoxo acid salt include salts of the above polyoxo acid with metals, ammonium, and organic amines. However, from the viewpoint of the polishing rate of the metal polishing aqueous dispersion in the present invention, the polyoxo acid is preferably in acid form rather than forming a salt.
The content of the polyoxo acid in the polishing aqueous dispersion of the present invention is not particularly limited, but is preferably used in the range of 0.1 to 30% by mass, more preferably 0.5 to 15% by mass. % Range. A sufficient polishing rate is exhibited when the content is 0.1% by mass or more, and polishing performance is good when the content is 30% by mass or less.
By using the nonionic surfactant used in the present invention in combination with the polyoxo acid, it is possible to suppress the progress of etching while maintaining a high polishing rate even at a low load, and to control the occurrence of dishing. It becomes possible. Surprisingly, this effect is preferable since it is noticeable when a nonionic surfactant having an HLB in the range of 5 to 12 is used.

Examples of such nonionic surfactants include those described in Table 2, page 2, page 52, "Sanyo Kasei Kogyo Co., Ltd." issued on November 1, 1985, "Introduction to New Surfactants". Any polyethylene glycol type and polyhydric alcohol type nonionic surfactant can be applied. Examples of the polyethylene glycol type nonionic surfactant include those obtained by adding a hydrophilic group by adding ethylene oxide to various hydrophobic groups, such as higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, fatty acid ethylene. Oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, higher alkylamine ethylene oxide adducts, fatty acid amide ethylene oxide adducts, fat and oil ethylene oxide adducts, polypropylene glycol ethylene oxide adducts, and the like. On the other hand, polyhydric alcohol type nonionic surfactants are those in which a hydrophobic fatty acid is bound to a hydrophilic polyhydric alcohol via an ester or amide group. The fatty acid ester of glycerol or the fatty acid ester of pentaerythritol. , Fatty acid esters of sorbitol and sorbitan, fatty acid esters of sucrose, fatty acid amides of alkanolamines, and the like.
Among these nonionic surfactants, those used in the present invention are preferably those having an HLB (hydrophile-balance balance) in the range of 5 to 12, but having an HLB of 5 or more. The hydrophobicity is appropriate, the dispersibility is good, and there are no problems such as sedimentation of particles and layer separation. On the other hand, when it is 12 or less, the hydrophilicity is appropriate, and it is effective for the formation of particles and has a good etching suppression effect.

  The nonionic surfactant of the present invention is preferably a polyoxyethylene ether of a higher alcohol having 8 to 24 carbon atoms, a polyoxyethylene ether of an alkylphenol, or a polyoxyethylene of polypropylene glycol classified as the polyethylene glycol type surfactant. Although oxyethylene ether (pluronic type) is mentioned, Polyoxyethylene ether of a higher alcohol having 8 to 24 carbon atoms is particularly preferable. Further, the polyoxyethylene ethers of the higher alcohols having 8 to 24 carbon atoms include an unsaturated type containing a carbon-carbon double bond in the molecule, such as an oleyl group, and a saturated type containing no carbon at all. However, a saturated higher alcohol polyoxyethylene ether is preferable because the saturated group is not easily affected by oxidation and does not deteriorate over time. Such as, for example, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene 2-ethylhexyl ether, polyoxyethylene tridecyl ether, polyoxyethylene Examples include isostearyl ether, polyoxyethylene synthetic alcohol ether (carbon number 12 to 15 in synthetic alcohol), and the like.

  Only one kind of these nonionic surfactants may be used, but by using two or more kinds of HLBs different from each other, the excellent performance of the aqueous dispersion for metal polishing of the present invention, that is, the generation is generated. High dispersibility and low etching property of abrasive particles, high-speed polishing property under a low load, and the like can be easily expressed. Furthermore, when two or more kinds of nonionic surfactants having different HLBs are used in combination, it is possible to mix each of them in advance or simultaneously with polyoxoacids, but preferably the HLB is high first. If one is mixed with polyoxoacid first, then the one with the lower HLB is mixed and adjusted, the low dispersibility of the generated abrasive particles is maintained and the high polishing performance at a low load is maintained. This is advantageous for expression.

The content of the nonionic surfactant used in the metal polishing aqueous dispersion of the present invention varies depending on the type and the type and amount of the polyoxo acid used, but is preferably in the range of 0.1 to 50% by mass. More preferably, it is the range of 0.5-25 mass%. When the content is 0.1% by mass or more, a sufficient anti-enching effect is exhibited and the occurrence of dishing can be controlled. Further, at 50% by mass or less, there is no problem such as an increase in viscosity, and handling is easy.
By including an anionic surfactant in the metal polishing aqueous dispersion of the present invention, it becomes possible to stably maintain the polishing performance of the aqueous dispersion (such as suppression of polishing rate and dishing), and the aqueous dispersion The storage stability of can be greatly improved. Even if an anionic surfactant is added to an aqueous polyoxoacid solution without adding the above-mentioned nonionic surfactant, a complex (fine particles) described later is not formed. That is, by adding an anionic surfactant after the addition of a nonionic surfactant, the effect of suppressing etching due to the formation of the composite (fine particles) described later is exhibited, and the storage stability of the aqueous dispersion for metal polishing is improved. It has been found that there is a significant improvement effect.

  The anionic surfactant used in the present invention is not particularly limited, but fatty acid or a salt thereof, alkylsulfonic acid or a salt thereof, alkylbenzenesulfonic acid or a salt thereof, alkylsulfosuccinic acid or a salt thereof, polyoxyethylene alkylsulfuric acid or Salt thereof, polyoxyethylene alkylaryl sulfate or salt thereof, p-styrenesulfonic acid or salt thereof, alkylnaphthalenesulfonic acid or salt thereof, naphthalenesulfonic acid or salt thereof, naphthenic acid or salt thereof, alkyl ether carboxylic acid or salt thereof Salt, α-olefin sulfonic acid or its salt, N-acylmethyl taurine, alkyl ether sulfuric acid or its salt, polyoxyethylene alkylphenyl ether sulfuric acid or its salt, alkyl ether phosphoric acid ester or its salt, Alkyl phosphoric acid ester, or a salt thereof, acylated peptides, formalin polycondensate, condensate of higher fatty acids and amino acids, monoglysulfate, secondary higher alcohol ethoxy sulfates, and the like dialkyl sulfosuccinate salts. In the present invention, a saturated type containing no carbon-carbon double bond (excluding a benzene ring) is preferable since it is not easily affected by oxidation and does not deteriorate in performance over time, alkylsulfonic acid or a salt thereof, Alkylbenzenesulfonic acid or a salt thereof, alkylsulfosuccinic acid or a salt thereof, polyoxyethylene alkylsulfuric acid or a salt thereof, polyoxyethylene alkylarylsulfuric acid or a salt thereof is preferably used. More preferably, alkylsulfonic acid, alkylbenzenesulfonic acid, alkylsulfosuccinic acid, polyoxyethylene alkylsulfuric acid, and polyoxyethylenealkylarylsulfuric acid are used.

In the present invention, from the viewpoint of polishing rate, the anionic surfactant is preferably an acid type rather than a salt.
In the present invention, the anionic surfactants can be used alone or in combination of two or more thereof.
The content of the anionic surfactant used in the metal polishing aqueous dispersion of the present invention varies depending on the type and the type and amount of the polyoxo acid and nonionic surfactant used, but preferably 0.1%. It is used in the range of ˜50 mass%, more preferably in the range of 0.3 to 20 mass%. When the amount is 0.1% by mass or more, a sufficient stabilizing effect of the composition is exhibited, and when it is 50% by mass or less, dishing is small, or there is no inconvenience such as an increase in viscosity.

The metal polishing aqueous dispersion of the present invention usually uses water as a medium. The polyoxoacid, nonionic surfactant and anionic surfactant are usually dissolved or dispersed by stirring, but a method of sufficiently dispersing using a homogenizer, ultrasonic wave, wet medium mill or the like is preferably used.
The aqueous dispersion for metal polishing prepared in this way is incorporated into micelles formed by the nonionic surfactant and the anionic surfactant due to the interaction between the polyoxoacid and the nonionic surfactant. A composite (fine particle) having such a structure is preferably present in a highly dispersed state in water. Basically, the composite here can be measured by a wet particle size analyzer as described later, and preferably has a number average particle size of 5 nm to 1 μm measured by a wet particle size analyzer. That is, from the viewpoint of smoothness of the polished surface obtained as a result of polishing using the metal polishing aqueous dispersion of the present invention, the particle size of the composite is preferably 1 μm or less, and from the viewpoint of polishing rate, 5 nm or more. It is preferable that

  Although the details of the polishing mechanism in the metal-based polishing aqueous dispersion of the present invention are not clear, composites (fine particles) formed by the interaction of polyoxoacid, nonionic surfactant and anionic surfactant are formed. , Acts as abrasive particles that develop a chemical polishing action (etching) due to the pressure generated between the polishing pad and the projection on the surface of the object to be polished, and maintains low etching properties in depressions where the pressure is low, thereby suppressing dishing It is considered that a very flat polished surface can be obtained by having the effect of. That is, the composite (fine particles) is considered to be in a state where polyoxo acid having a strong etching action is covered with a protective film of a nonionic surfactant and an anionic surfactant. Therefore, the composite (fine particles) is essentially different in character from the abrasive grains conventionally used for the purpose of mechanical polishing. The settling of abrasive grains is eliminated.

  Furthermore, in a conventional polishing composition that requires mechanical polishing with abrasive grains, it is known that the polishing rate is proportional to the polishing pressure. However, when the metal polishing aqueous dispersion of the present invention is used, polishing is performed. The speed is not proportional to the polishing pressure. The polishing does not proceed below a certain threshold of the polishing pressure, and a high polishing speed can be obtained at a polishing pressure exceeding the threshold. The threshold value varies depending on the composition of the metal polishing aqueous dispersion of the present invention. By selecting a composition having a low threshold value, a high polishing rate can be obtained at a low polishing pressure. Problems such as damage to the substrate are eliminated. In the present invention, it is preferable to contain an organic compound having both a nitrogen atom and a carboxyl group in the molecule from the viewpoint of suppressing dishing. Organic compounds having nitrogen and carboxyl groups in the molecule include cystine, glycine, glutamic acid, aspartic acid, quinaldic acid, quinolinic acid, picolinic acid, nicotinic acid, histidine, benzotriazole carboxylic acid, glutamine, glutathione, glycylglycine , Alanine, γ-aminobutyric acid, ε-aminocaproic acid, arginine, titrulline, tryptophan, threonine, cysteine, N-acetylcysteine, oxyproline, isoleucine, leucine, lysine, methionine, phenylalanine, phenylglycine, proline, serine, tyrosine, Preferred examples include valine, and more preferred examples include quinaldic acid and histidine.

The addition amount of the organic compound having both a nitrogen atom and a carboxyl group in the molecule is 0 to 5000 ppm, preferably 0 to 1000 ppm, more preferably 0 to 200 ppm, from the viewpoint of polishing rate and from the viewpoint of expression of dishing suppression effect. It is as follows.
Including the water-soluble polymer compound and / or polyhydric alcohol compound in the metal polishing aqueous dispersion of the present invention is preferable from the viewpoint of improving the polishing uniformity of the resulting polished surface.
Examples of water-soluble polymers used in the present invention include ethers such as polyethylene glycol, polypropylene glycol, and polyethylene glycol alkyl ether; vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrolein; polyacrylic acid, polymethacrylic acid, poly Polycarboxylic acids such as acrylamide, polyamic acid, ammonium polyacrylate and salts thereof; polysaccharides such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, cellulose acetate, cellulose nitrate, cellulose sulfate, pectin, gelatin in others; Starch, albumin, and the like are preferable examples. Polyethylene glycol, hydroxyethyl cellulose, hydroxypropyl Cellulose, carboxymethyl cellulose, but are mentioned as more preferable examples.

In the present invention, the polyhydric alcohol compound is a low molecular compound other than the above water-soluble polymer compound, and means a compound having a plurality of hydroxyl groups in one molecule, such as ethylene glycol, glycerin, propanediol, pentaerythritol, and fructose. Sucrose, diethylene glycol, triethylene glycol and the like are preferable examples, and ethylene glycol, glycerin, diethylene glycol and triethylene glycol are more preferable examples.
The content of the water-soluble polymer compound and / or polyhydric alcohol compound used in the metal polishing aqueous dispersion of the present invention varies depending on the type and the type and amount of the polyoxo acid used, but is preferably 0.01. It is the range of -50 mass%, More preferably, it is the range of 0.1-20 wt%. That is, 0.01% by mass or more is preferable from the viewpoint of the effect of addition, and 50% by mass or less is preferable from the viewpoint of increase in viscosity due to addition.

  Since the metal polishing aqueous dispersion of the present invention has a very low etching property of the metal film that causes dishing, it is usually not necessary to use a protective film forming agent, but it does not substantially reduce the polishing rate. If necessary, it is also possible to add a compound that forms a chelate or complex with the metal film to further suppress the etching property. In particular, 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. Other examples of the anticorrosive include benzotriazole derivatives such as tolyltriazole and benzotriazole carboxylic acid, cystine, haloacetic acid, glucose, dodecyl mercaptan and the like. The amount of these anticorrosives added is 0 to 100 ppm or less, preferably 0 to 50 ppm or less, and a very small amount is sufficient as compared with the amount used in conventional abrasives. On the other hand, if the amount added is large, the polishing rate is lowered and the desired polishing performance cannot be obtained, which is not preferable.

The metal-dispersed aqueous dispersion of the present invention may contain a known oxidizing agent within a range that does not cause excessive etching for the purpose of further improving the polishing rate of the metal film. Examples of the oxidizing agent to be contained include known oxidizing agents such as peroxides such as hydrogen peroxide, perchloric acid, perchlorate, periodic acid, periodate, persulfuric acid, persulfate, and nitrate. Can be mentioned.
The metal-polishing aqueous dispersion in the present invention may contain an acid if necessary, and the polishing performance of the metal film can be controlled by the type of acid used and the pH of the obtained metal-polishing aqueous dispersion. . Examples of the acid contained include known inorganic acids such as sulfuric acid, phosphoric acid, and nitric acid, or known organic acids such as oxalic acid, citric acid, malic acid, and acetic acid.
A water-soluble alcohol such as methanol, ethanol, n-propanol, iso-propanol, ethylene glycol, glycerin or the like can be added to the metal polishing aqueous dispersion of the present invention as necessary.

The aqueous dispersion for metal polishing 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 metal film for wiring, plug, contact metal layer, barrier metal layer, for example, aluminum, copper, tungsten, titanium, tantalum, aluminum alloy, copper alloy And a metal film selected from the group consisting of titanium nitride, tantalum nitride, and the like. In particular, application to a metal film made of copper or a copper alloy, which has a low surface hardness and is liable to cause defects such as scratches and dishing, is recommended.
As shown in FIG. 1C, for the semiconductor substrate obtained by embedding the wiring metal film 4, as shown in FIG. 1D, an extra metal film other than the groove or opening is formed on the polyoxoacid. It is removed and flattened by polishing with a metal polishing aqueous dispersion containing composite particles formed from a nonionic surfactant and a nonionic surfactant.

The method for producing a semiconductor substrate of the present invention comprises polishing a metal film on a semiconductor substrate such as a silicon substrate containing composite particles formed from a polyoxoacid, a nonionic surfactant and a nonionic surfactant. It comprises a process of polishing with an aqueous dispersion. Hereinafter, a method for manufacturing the semiconductor substrate will be described.
First, as shown in FIG. 1A, after an insulating film 2 is formed on a semiconductor substrate 1 such as a silicon substrate, a groove for metal wiring or a connection wiring is formed in the insulating film 2 by a photolithography method and an etching method. An opening 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, as shown in FIG. 1C, a metal film 4 for wiring is embedded so that the thickness is equal to or greater than the height of the groove or opening formed in the insulating film 2. Next, as shown in FIG. 1 (D), a metal containing composite particles in which an extra metal film other than a groove or an opening is formed from a polyoxo acid, a nonionic surfactant, and an anionic surfactant. It is removed by a method of polishing using a polishing aqueous dispersion. Furthermore, by forming an insulating film on the obtained flattened surface and repeating the above method as many times as necessary, a semiconductor substrate having a multilayer wiring structure as an electronic component can be obtained.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not restrict | limited by these.
The particle diameter measurement and polishing performance evaluation of the metal polishing aqueous dispersion were performed by the following methods.
<Particle size measurement>
(1) Fine (less than 5 μm) particles: Measured using a wet particle size analyzer Nikkiso Co., Ltd. Microtrac UPA-9230).
(2) Coarse (5 μm or more) particles: Measured using a wet particle size analyzer, Horiba LA-700.
In addition, the average particle diameter shown after this means the particle diameter by a number average.
<Polishing speed measurement>
The change in each film thickness before and after polishing was calculated by dividing by the polishing time.
The polishing conditions were: polishing pressure 50 g / cm ² , relative speed between substrate and polishing pad 50 m / min, IC1400A21 (Rodel Nitta Co., Ltd.) dressed with a No. 100 dresser as a polishing pad, and metal on the polishing pad A silicon wafer with a copper film (thickness: 1 μm) was polished for 1 minute while dropping a polishing aqueous dispersion at 200 ml / min.

<Evaluation of surface defects (scratches)>
After the silicon wafer polished by the above <Polishing speed measurement> was washed and dried, a spotlight was applied to the surface of the semiconductor wafer in a dark room, and the presence or absence of scratch was visually determined.
<Dishing performance evaluation by etching rate measurement>
By evaluating wet etching, which is the cause of dishing, alternative evaluation of dishing was made. That is, dishing is caused by the erosion of the metal film due to excessive chemical action (wet etching) of the polishing composition, so the etching rate of the polishing composition, which is the main cause of dishing, is reduced. Evaluation here results in evaluation of dishing performance.

Specifically, the etching rate referred to in the present invention refers to a substrate on which a metal film is formed in a test solution prepared by dissolving a substance to be tested in advance so as to have a predetermined concentration. Is the thickness of the metal film that disappears after a certain period of time. Specifically, 800 ml of polishing liquid is filled in a cylindrical container having an inner diameter of 10 cm, and a homogenizer ULTRA-TURRAX T8 (shaft S8N-8G) manufactured by IKA-WERKE is placed in the center of the cylindrical container and stirred at 25000 rpm. In a test solution, a 5 mm square substrate piece with a metal film formed on a Si wafer is placed vertically, fixed at a position where both ends of the substrate piece are in contact with the wall of the container, and immersed for about 3 minutes. The thickness of the film (metal film on the surface at the center of the container) was measured, the thickness of the metal film disappeared per unit time was calculated to determine the etching rate, and the dishing property was evaluated according to the following criteria (◎ to ×). The slower the etching rate, the weaker the wet etching property and the less likely dishing occurs.
A: Less than 3 nm / min etching rate B: Etching rate 3-10 nm / min Δ: Etching rate 10 nm / min to 50 nm / min X: Etching rate 50 nm / min

<Evaluation of storage stability of aqueous dispersion for metal polishing>
As the storage stability evaluation after leaving the aqueous metal dispersion for metal polishing at room temperature for 1 month, the following determination was made.
○: Change rate of polishing rate and etching rate is less than 5% Δ: Change rate of polishing rate and etching rate is 5% or more and less than 20% ×: Change rate of polishing rate and etching rate is 20% or more <In-plane uniformity Evaluation>
After cleaning and drying the silicon wafer polished in the above <Polishing speed measurement>, a spotlight was applied to the wafer surface in a dark room, and the uniformity of the polishing state of the entire wafer surface was visually determined.
◎: Very good uniformity ○: Good uniformity △: Partially non-uniform polishing state is confirmed ×: Poor uniformity

[Example 1]
As the polyoxoacid, 12 g of phosphovanadmolybdic acid: PVMo (trade name: PVM-1-11 manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) (hereinafter referred to as PVMo) was dissolved in 176 g of water and stirred with a homogenizer. After adding 8 g of polyoxyethylene synthetic alcohol ether: SF-1 (trade name BLAUNON DAL-5, HLB = 10.7, manufactured by Aoki Yushi Kogyo Co., Ltd.) (hereinafter referred to as SF-1), an anionic surfactant 4 g of dodecylbenzenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added to obtain an aqueous dispersion for metal polishing. The average particle size of this composition measured by UPA-9230 was about 100 nm. The evaluation results are shown in Table 1.
[Example 2]
Example 1 except that polyoxyethylene oleyl ether: SF-2 (trade name: BLAUNON EN-905, HLB = 8.9, manufactured by Aoki Yushi Kogyo Co., Ltd.) is used as a nonionic surfactant instead of SF-1. In the same manner as above, an aqueous dispersion for metal polishing was obtained. The average particle size of this composition measured by UPA-9230 was about 80 nm. The evaluation results are shown in Table 1.

[Example 3]
0.02 g of histidine (manufactured by Wako Pure Chemical Industries, Ltd.) was added to and mixed with the metal polishing aqueous dispersion obtained in Example 2 to obtain a metal polishing aqueous dispersion. The average particle size of this composition as measured by UPA-9230 was about 80 nm as in the case of the metal polishing aqueous dispersion obtained in Example 2. The evaluation results are shown in Table 1.
[Example 4]
An aqueous metal polishing dispersion was obtained in the same manner as in Example 1 except that silmomolybdic acid: SiMo (trade name SM, manufactured by Nippon Inorganic Chemical Industry Co., Ltd.) was used as the polyoxo acid. The average particle diameter of this composition measured by UPA-9230 was about 70 nm. The evaluation results are shown in Table 1.

[Example 5]
Instead of SF-1 as a nonionic surfactant, polyoxyethylene synthetic alcohol ether: SF-3 (trade name BLAUNON OX-20, HLB = 5.7, manufactured by Aoki Yushi Kogyo Co., Ltd.) (hereinafter referred to as SF-3) ) A metal-polishing aqueous dispersion was obtained in the same manner as in Example 1 except that 8 g was used. The average particle diameter of this composition measured by UPA-9230 was about 200 nm. The evaluation results are shown in Table 1.
[Example 6]
12 g of PVMo as a polyoxo acid was dissolved in 176 g of water, and 4 g of SF-1 as a nonionic surfactant was added thereto while stirring with a homogenizer. Next, a nonionic surfactant: SF-3 was added thereto. Then, 4 g of dodecylbenzenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an anionic surfactant and mixed to obtain an aqueous dispersion for metal polishing. The average particle size of this composition measured by UPA-9230 was about 30 nm. The evaluation results are shown in Table 1.

[Example 7]
12 g of PVMo as polyoxo acid was dissolved in 168 g of water and stirred with a homogenizer. Polyoxyethylene cetyl ether: SF-4 (trade name BLAUNON CH-305, HLB = 9.4, as a nonionic surfactant was added thereto. Aoki Yushi Kogyo Co., Ltd.) (hereinafter referred to as SF-4) 8 g mixed with 52 g of pure water was added, and then polyoxyethylene 2-ethylhexyl ether: SF-5 (product) as a nonionic surfactant Name BLAUNON EH-2, HLB = 8.1, manufactured by Aoki Yushi Kogyo Co., Ltd.) 3 g mixed with 57 g of pure water was added, followed by dodecylbenzenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) as an anionic surfactant 3g is added, and further 20g of diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) is added and mixed. Got the body. The average particle size of this composition measured by UPA-9230 was about 230 nm. The evaluation results are shown in Table 1.

[Example 8]
As a polyoxoacid, 12 g of PVMo was dissolved in 168 g of water, and a mixture of 6 g of nonionic surfactant: SF-4 mixed with 54 g of pure water was added to this while stirring with a homogenizer. After adding 2 g of polyoxyethylene synthetic alcohol ether: SF-6 (trade name BLAUNON OX-20, HLB = 5.7, manufactured by Aoki Yushi Kogyo Co., Ltd.) as pure surfactant to 58 g of pure water, anion 3 g of dodecylbenzenesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) as a surfactant, and 5 g of polyethylene glycol (average molecular weight 8000, manufactured by Wako Pure Chemical Industries, Ltd.) are added and mixed to obtain an aqueous dispersion for metal polishing. Got. The average particle size of this composition measured by UPA-9230 was about 120 nm. The evaluation results are shown in Table 1.

[Comparative Example 1]
As a polyoxoacid, 12 g of PVMo was dissolved in 200 g of water to obtain a composition. This composition became a uniform solution, and the particle size could not be measured. The evaluation results are shown in Table 1.
[Comparative Example 2]
A composition was obtained in exactly the same manner as in Example 1 except that the same amount of lauryltrimethylammonium chloride: SF-7 was used as the cationic surfactant instead of the nonionic surfactant. The average particle diameter of this composition measured by LA-700 was about 5 μm. The evaluation results are shown in Table 1. In addition, sedimentation of the particles was confirmed after leaving this composition for 1 day.

[Comparative Example 3]
A composition was obtained in exactly the same manner as in Example 1 except that the anionic surfactant (dodecylbenzenesulfonic acid) was not added. The average particle size of this composition measured by UPA-9230 was about 300 nm. The evaluation results are shown in Table 1.
[Comparative Example 4] 6 g of citric acid was added to 162 g of water and dissolved, and a solution obtained by dissolving 0.4 g of benzotriazole (BTA) in 3 g of ethanol was added thereto. Further, colloidal silica (average particle size of 40 nm, 60 g of silica concentration 20%, manufactured by Nissan Chemical Industries, Ltd.) was added, and finally 28 g of hydrogen peroxide water (special grade reagent, 30% aqueous solution) was added to prepare an aqueous dispersion for metal polishing. The average particle diameter of this composition measured by UPA-9230 was about 40 nm. The evaluation results of this composition are shown in Table 1.

It is a schematic sectional drawing which shows the example of formation of the metal wiring using CMP technique.

Explanation of symbols

1 Semiconductor substrate 2 Insulating film 3 Barrier metal layer 4 Metal film

Claims (9)

  An aqueous dispersion for metal polishing comprising composite particles formed from a polyoxoacid, a nonionic surfactant, and an anionic surfactant.   The aqueous dispersion for metal polishing according to claim 1, wherein the polyoxo acid is a heteropoly acid.   The aqueous dispersion for metal polishing according to claim 1 or 2, wherein the anionic surfactant is in an acid form.   The aqueous dispersion for metal polishing according to any one of claims 1 to 3, wherein two or more kinds of nonionic surfactants having different HLBs are used in combination as the nonionic surfactant.   The water-based dispersion for metal polishing according to claim 1, comprising a water-soluble polymer compound and / or a polyhydric alcohol compound.   The aqueous dispersion for metal polishing according to any one of claims 1 to 5, comprising an organic compound having both a nitrogen atom and a carboxyl group in the molecule.   The aqueous dispersion for metal polishing according to any one of claims 1 to 6, which is substantially free of abrasive grains.   A method for polishing a metal film on a semiconductor substrate, comprising using the metal-based polishing aqueous dispersion according to claim 1.   A method for producing a semiconductor substrate, comprising using the metal polishing aqueous dispersion according to claim 1.

Images