JP2007095840A - Chemical mechanical polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chemical mechanical polishing method for continuously polishing a conductive film and a barrier metal film with a same pad with excellent processing efficiency, concerning a process for polishing the metal wiring of copper or an alloy with the copper as a main component, etc., in a semiconductor wiring manufacturing process. <P>SOLUTION: The chemical mechanical polishing method is the method for polishing a semiconductor integrated circuit having the barrier metal film and the conductive film arranged on the former film. The barrier metal film and the conductive film are continuously polished on the same polishing pad. A polishing solution A for polishing the conductive film contains an oxidizer but does not contain inorganic abrasive grains. A polishing solution B for polishing the barrier metallic film contains the oxidizer and the inorganic abrasive grains. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a chemical mechanical polishing method for semiconductor devices. More particularly, the present invention relates to a chemical mechanical polishing method capable of efficient processing during polishing of a semiconductor device.

  Copper is a low resistance material in the formation of semiconductor integrated circuits where miniaturization and high density are accelerated, and in recent years, it has attracted much attention as a very useful electrical connection material. Currently, the formation of wiring using copper and an alloy containing copper as a main component is generally formed as follows.

  That is, after forming recesses such as grooves and connection holes in the insulating film, forming a barrier metal film, a copper film is formed by plating so as to fill the recesses, and then chemical mechanical polishing (hereinafter referred to as chemical mechanical polishing) The surface of the insulating film other than the recess is polished by CMP until the surface is completely exposed, and the surface is flattened to form an electrical connection portion such as a buried copper wiring, via plug, or contact plug in which copper is embedded in the recess.

  Hereinafter, a method for forming a buried copper wiring will be described with reference to FIGS. A lower wiring layer 1 made of an insulating film having a lower wiring (not shown) is formed on a silicon substrate (not shown). As shown in FIG. 1A, a silicon nitride film 2 is chemically formed on the lower wiring layer 1. The insulating film 3 is formed in this order by a chemical vapor deposition (CVD) method or a coating method by vapor deposition (CVD). Next, a recess having a wiring pattern shape and reaching the silicon nitride film 2 is formed in the insulating film 3 as shown in FIG. Subsequently, as shown in FIG. 1C, a barrier metal film 4 is formed by a sputtering method. Subsequently, as shown in FIG. 1D, a copper film 5 is formed on the entire surface by electrolytic plating so that the concave portions are embedded. Thereafter, as shown in FIG. 1E, the copper film 5 is polished by CMP to flatten the substrate surface. Subsequently, as shown in FIG. 1F, polishing by CMP is continued until the barrier metal on the silicon oxide film 3 is completely removed.

  A general method of CMP is to rotate a circular polishing platen (platen) to which a polishing pad is attached while dripping and holding the polishing liquid on the surface of the polishing pad, and further to the surface of the substrate (wafer) on the pad surface. The substrate is rotated with a predetermined pressure (polishing pressure) applied from the back surface thereof, and the surface of the substrate is flattened by mechanical friction generated by the relative movement between the polishing platen and the substrate.

  The metal polishing solution used for CMP generally contains abrasive grains (for example, alumina and silica) and an oxidizing agent (for example, hydrogen peroxide and persulfuric acid).

  However, when CMP is performed using a metal polishing liquid containing such solid abrasive grains, scratches (scratches), a phenomenon in which the entire polished surface is polished more than necessary (thinning), and the polished metal surface is dish-shaped. In some cases, a phenomenon of depression (dishing), an insulator between metal wirings is polished more than necessary, and a phenomenon that a plurality of wiring metal surfaces are recessed on a plate (erosion) may occur. Further, in order to remove the polishing liquid remaining on the surface of the substrate, which is the surface to be polished, after polishing, a step of washing by dropping / supplying ultrapure water continuously after the polishing liquid is required after polishing ( Called water polishing).

  Further, during polishing, solid abrasive grains and polishing scraps (polishing products) are deposited on the polishing pad, reducing the holding power of the polishing liquid on the polishing pad surface, resulting in a decrease in polishing efficiency. Furthermore, this deposit also causes scratches on the surface to be polished, which is a serious problem in polishing.

  Therefore, it is necessary to remove the accumulated solid abrasive grains and polishing scraps before performing the next polishing, which is called dressing or conditioning (hereinafter referred to as conditioning). For the conditioning of the pad, a grindstone called a pad conditioner is generally used. For example, there is one disclosed in Patent Document 1. In this pad conditioner, an abrasive layer in which diamond abrasive grains are fixed with a metallic binder phase such as nickel is formed on the surface of a substantially disk-shaped substrate made of iron or stainless steel. The abrasive layer is formed so as to extend radially from the vicinity of the center of the surface of the substrate toward the outer peripheral side. Then, by pressing the surface of the substrate against the surface of the pad rotated about the axis line with a constant load, the substrate rotates in accordance with the rotational movement of the pad, and the abrasive grains on the surface The surface of the pad is cut by the layer to remove surface deposits.

  As described above, water polishing and conditioning of the polishing pad are necessary after polishing, and it is desirable to omit these steps when considering the efficiency of the polishing process. Furthermore, in the conventional main method, the CMP is divided into two stages, that is, Cu-CMP corresponding to FIGS. 1D to 1E and barrier CMP corresponding to FIGS. 1E to 1F. Polishing is performed with different polishing liquids and pads (polish rooms) (see also FIG. 3 described later).

  The main reason is that the optimum polishing pad type and pad conditioning conditions differ depending on the polishing liquid. The term “optimal” as used herein refers to a state in which polishing characteristics such as polishing speed, flattening characteristics, and the presence or absence of scratches are comprehensively adjusted.

  In this specification, the polishing liquid used in FIGS. 1D to 1E is called a conductive film polishing liquid, which changes from the state of FIG. 1D to the state of FIG. This is a polishing liquid used for the purpose, and is not necessarily a polishing liquid that cannot polish the barrier metal film. Similarly, the polishing liquid used in FIGS. 1E to 1F is referred to as a barrier polishing liquid, which is used to change from the state of FIG. 1E to the state of FIG. This is not necessarily a polishing liquid that cannot polish the conductor film.

As described above, it is not preferable to perform Cu-CMP and barrier CMP separately in terms of transport time between chambers, cleaning time of each chamber, conditioning time, and the like, and improving the efficiency of CMP processing. .
Japanese Patent Laid-Open No. 10-193269

  The present invention aims to solve the above problems. That is, the present invention is excellent in processing efficiency in the step of polishing a metal wiring such as copper and a copper-based alloy in the semiconductor wiring manufacturing process, and the conductor film and the barrier metal film (barrier film) are the same pad. It is an object of the present invention to provide a chemical mechanical polishing method in which polishing is continuously performed with the above method.

  As a result of intensive studies, the present inventor has found that the above problem can be solved by appropriately using a polishing liquid that does not contain inorganic abrasive grains and a polishing liquid that contains inorganic abrasive grains, and has achieved the object. That is, the present invention is as follows.

(1) A chemical mechanical polishing method for polishing a semiconductor integrated circuit having a barrier metal film and a conductor film thereon, wherein the barrier metal film and the conductor film are continuously formed on one polishing pad. The polishing liquid A that polishes and polishes the conductor film is a polishing liquid that contains an oxidizing agent and does not contain inorganic abrasive grains, and the polishing liquid B that polishes the barrier metal film contains an oxidizing agent and inorganic abrasive grains. A chemical mechanical polishing method, characterized by being a polishing liquid.

(2) The method further includes a conditioning process for removing solid abrasive grains and polishing debris deposited on the polishing pad, wherein the pressing load applied to the pad of the conditioner used in the conditioning process is 60 hPa or more (1) The chemical mechanical polishing method described in 1.
(3) The inorganic abrasive grains of the polishing liquid B are particles selected from the group consisting of fumed silica, colloidal silica, synthetic silica, ceria, alumina, titania, zirconia, germania, manganese oxide, and silicon carbide. (1) The chemical mechanical polishing method according to (1).
(4) The oxidizing agent of the polishing liquid A and the oxidizing agent of the polishing liquid B are hydrogen peroxide, peroxide, nitrate, iodate, periodate, hypochlorite, chlorite, respectively. Any one selected from the group consisting of chlorate, perchlorate, persulfate, dichromate, permanganate, ozone water, silver (II) salt and iron (III) salt (1) The chemical mechanical polishing method according to (1).

  In the present invention, since the polishing liquid A does not substantially contain abrasive grains, clogging due to abrasive grains in the polishing pad holes during polishing of the conductive film is suppressed, and the polishing rate does not decrease. In addition, the occurrence of scratches on the polished surface can be suppressed by suppressing the clogging. Furthermore, it becomes possible to reduce the conditioning load by controlling clogging. Therefore, even if Cu-CMP and barrier CMP are continuously performed in the same chamber (pad), high-quality polishing with few scratches can be achieved without increasing the processing time and reducing the life of the consumable member. Can be done. In general, as shown in FIG. 3, after Cu-CMP is performed, the wafer is transferred to a different pad and then barrier CMP is performed. In the present invention, as shown in FIG. CMP and barrier CMP are continuously performed. Therefore, the conveyance time can be shortened, the processing time can be shortened, the consumable members can be unified, the consumable member life can be extended, and the process can be simplified.

  According to the present invention, in the process of polishing metal wiring such as copper and copper-based alloy in the semiconductor wiring manufacturing process, the processing efficiency is excellent, and the conductor film and the barrier film are continuously polished with the same pad. A chemical mechanical polishing method is provided.

  The metal polishing liquid used in the chemical mechanical polishing method of the present invention will be described below.

(Metal polishing liquid)
[Polishing liquid A (for conductor film polishing)]
The polishing liquid A used in the chemical mechanical polishing method of the present invention does not contain inorganic abrasive grains. That is, the polishing liquid A in the present invention reduces polishing scratches on the object to be polished because CMP proceeds by friction with a polishing pad that is much mechanically softer than solid abrasive grains, even if it does not contain solid abrasive grains. . The inorganic abrasive component may coexist as long as the effect of the present invention is not impaired, in other words, the inorganic abrasive particle does not substantially function. In this case, the inorganic abrasive concentration cannot be generally specified, but is generally 0.2 wt% or less.

  The polishing liquid A contains an oxidizing agent as an essential component. Specific examples of oxidizing agents include hydrogen peroxide, peroxide, nitrate, iodate, periodate, hypochlorite, chlorite, chlorate, perchlorate, persulfate , Dichromate, permanganate, ozone water, silver (II) salt and iron (III) salt, and hydrogen peroxide is more preferably used.

  The addition amount of the oxidizing agent is preferably 0.003 mol to 8 mol, more preferably 0.03 mol to 6 mol, and more preferably 0.1 mol to 4 mol in 1 liter of the metal polishing liquid used for polishing. It is particularly preferable to do this. That is, the addition amount of the oxidizing agent is preferably 0.003 mol or more from the viewpoint of sufficient metal oxidation and ensuring a high CMP rate, and is preferably 8 mol or less from the viewpoint of preventing roughening of the polished surface.

  Furthermore, it is preferable that the polishing liquid A contains an organic acid and an immobile film forming agent. Suitable organic acids are preferably water-soluble, such as amino acids and other acids. As the amino acid, one selected from the following group is more suitable.

  Glycine, L-alanine, β-alanine, L-2-aminobutyric acid, L-norvaline, L-valine, L-leucine, L-norleucine, L-isoleucine, L-alloisoleucine, L-phenylalanine, L-proline, Sarcosine, L-ornithine, L-lysine, taurine, L-serine, L-threonine, L-allothreonine, L-homoserine, L-tyrosine, 3,5-diodo-L-tyrosine, β- (3 4-dihydroxyphenyl) -L-alanine, L-thyroxine, 4-hydroxy-L-proline, L-cystine, L-methionine, L-ethionine, L-lanthionine, L-cystathionine, L-cystine, L-cysteic acid , L-aspartic acid, L-glutamic acid, S- (carboxymethyl) -L-cysteine, 4-aminobutyric acid, L Asparagine, L-glutamine, azaserine, L-arginine, L-canavanine, L-citrulline, δ-hydroxy-L-lysine, creatine, L-quinurenin, L-histidine, 1-methyl-L-histidine, 3-methyl -Amino acids such as L-histidine, ergothioneine, L-tryptophan, actinomycin C1, apamin, angiotensin I, angiotensin II and antipine.

  As organic acids other than amino acids, those selected from the following group are more suitable. Formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid , N-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, Examples thereof include tartaric acid, citric acid, lactic acid, hydroxyethyliminodiacetic acid, iminodiacetic acid, dihydroxyethylglycine, and salts such as ammonium salts and alkali metal salts thereof. Among these, malic acid, tartaric acid, citric acid, hydroxyethyliminodiacetic acid, iminodiacetic acid, dihydroxyethylglycine and the like are preferable in that the etching rate can be effectively suppressed while maintaining a practical CMP rate, Is preferred.

  The addition amount of the organic acid is preferably 0.0005 to 0.5 mol, more preferably 0.005 mol to 0.3 mol, and more preferably 0.01 mol to 1 mol in 1 L of the polishing liquid used for polishing. The amount is particularly preferably 0.1 mol. That is, the amount of acid added is preferably 0.5 mol or less from the viewpoint of suppressing etching, and 0.0005 mol or more is preferable for obtaining a sufficient effect.

  A suitable immobile film-forming agent to be contained in the polishing liquid A is a heterocyclic compound. A heterocyclic compound is a compound having a heterocyclic ring containing a hetero atom. The number of heteroatoms contained in the compound having a heterocycle is not limited, but is preferably 2 or more, more preferably 4 or more heteroatoms. In particular, it is preferable to use a heterocyclic compound containing 3 or more nitrogen atoms, and using a heterocyclic compound containing 4 or more nitrogen atoms is preferable because the remarkable effects of the present invention can be obtained.

  Further, the heterocyclic ring may be a single ring or a polycyclic ring having a condensed ring. The number of members in the case of a single ring is preferably 5 to 7, particularly preferably 5. In the case of having a condensed ring, the number of rings is preferably 2 or 3.

  Specific examples of these heterocyclic rings include the following. That is, pyrrole ring, thiophene ring, furan ring, pyran ring, thiopyran ring, imidazole ring, pyrazole ring, thiazole ring, isothiazole ring, oxazole ring, isoxazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, pyrrolidine Ring, pyrazolidine ring, imidazolidine ring, isoxazolidine ring, isothiazolidine ring, piperidine ring, piperazine ring, morpholine ring, thiomorpholine ring, chroman ring, thiochroman ring, isochroman ring, isothiochroman ring, indoline ring, isoindoline ring , Pyridine ring, indolizine ring, indole ring, indazole ring, purine ring, quinolidine ring, isoquinoline ring, quinoline ring, naphthyridine ring, phthalazine ring, quinoxaline ring, quinazoline ring, cinnoline ring, pteridine ring, Kridine ring, perimidine ring, phenanthroline ring, carbazole ring, carboline ring, phenazine ring, anti-lysine ring, thiadiazole ring, oxadiazole ring, triazine ring, triazole ring, tetrazole ring, benzimidazole ring, benzoxazole ring, benzthiazole ring Benzthiadiazole ring, benzfuroxan ring, naphthimidazole ring, benztriazole ring, tetraazaindene ring and the like, more preferably triazole ring and tetrazole ring.

  Examples of the substituent that can be introduced into the heterocyclic compound used in the present invention include the following.

  Examples of the substituent that the heterocyclic ring may have include, for example, a halogen atom, an alkyl group (a linear, branched or cyclic alkyl group, and an active methine group, even a polycyclic alkyl group such as a bicycloalkyl group). Or an alkenyl group, an alkynyl group, an aryl group, an amino group, or a heterocyclic group. Furthermore, two or more of a plurality of substituents may be bonded to each other to form a ring, and for example, an aromatic ring, an aliphatic hydrocarbon ring, a heterocyclic ring, or the like can be formed.

  Specific examples of the heterocyclic compound that can be particularly preferably used in the present invention include, but are not limited to, the following. That is, 1,2,3,4-tetrazole, 5-amino-1,2,3,4-tetrazole, 5-methyl-1,2,3,4-tetrazole, 1,2,3-triazole, 4- Amino-1,2,3-triazole, 4,5-diamino-1,2,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3,5-diamino- 1,2,4-triazole and benzotriazole.

  The heterocyclic compounds used in the present invention may be used alone or in combination of two or more. Moreover, the heterocyclic compound used by this invention can be synthesize | combined according to a conventional method, and may use a commercial item. The total amount of the heterocyclic compound used in the present invention is the metal polishing liquid used for polishing (that is, the metal polishing liquid after dilution when diluted with water or an aqueous solution. In 1 L of “the metal polishing liquid”, 0.0001 to 0.1 mol is preferable, more preferably 0.0005 to 0.05 mol, and still more preferably 0.0005 to 0.01 mol. is there.

  The polishing liquid A of the present invention may further contain other components, and examples thereof include a surfactant, a hydrophilic polymer, and other additives.

  Both the surfactant and the hydrophilic polymer have the action of reducing the contact angle of the surface to be polished and the action of promoting uniform polishing. As the surfactant and the hydrophilic polymer used, those selected from the following groups are suitable.

  Examples of the anionic surfactant include carboxylate, sulfonate, sulfate ester salt and phosphate ester salt. Examples of the cationic surfactant include aliphatic amine salt, aliphatic quaternary ammonium salt, benzalkonium chloride. Salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and amphoteric surfactants include carboxybetaine type, aminocarboxylate, imidazolinium betaine, lecithin, alkylamine oxide, nonionic interface Examples of the activator include an ether type, an ether ester type, an ester type, and a nitrogen-containing type, and also include a fluorine-based surfactant.

  Furthermore, examples of the hydrophilic polymer include polyglycols such as polyethylene glycol, polysaccharides such as polyvinyl alcohol, polovinyl pyrrolidone, and alginic acid, and carboxylic acid-containing polymers such as polymethacrylic acid.

  Of the above, the acid or its ammonium salt is preferably free from contamination by alkali metals, alkaline earth metals, halides and the like. Among the above exemplified compounds, cyclohexanol, polyacrylic acid ammonium salt, polyvinyl alcohol, succinic acid amide, polo vinyl pyrrolidone, polyethylene glycol, and polyoxyethylene polyoxypropylene block polymer are more preferable.

  The weight average molecular weight of these surfactants and hydrophilic polymers is preferably from 500 to 100,000, particularly preferably from 2,000 to 50,000.

  The total amount of the surfactant and / or hydrophilic polymer added is preferably 0.001 to 10 g and preferably 0.01 to 5 g in 1 liter of the metal polishing slurry used for polishing. Is more preferably 0.1 to 3 g.

  The metal polishing liquid is preferably added with an alkali / acid or a buffer so as to have a predetermined pH. Alkali / acid or buffering agents include organic ammonium hydroxides such as ammonium hydroxide and tetramethylammonium hydroxide, nonmetallic alkaline agents such as alkanolamines such as diethanolamine, triethanolamine, triisopropanolamine, water Alkali metal hydroxides such as sodium oxide, potassium hydroxide and lithium hydroxide, inorganic acids such as nitric acid, sulfuric acid and phosphoric acid, carbonates such as sodium carbonate, phosphates and borates such as trisodium phosphate, Preferable examples include tetraborate and hydroxybenzoate. Particularly preferred alkali agents are ammonium hydroxide, potassium hydroxide, lithium hydroxide and tetramethylammonium hydroxide.

The addition amount of the alkali / acid or buffer may be an amount that can maintain the pH within a preferable range, and should be 0.0001 mol to 1.0 mol in 1 L of the metal polishing slurry used for polishing. Is preferably 0.003 mol to 0.5 mol.
3-12 are preferable, as for pH of the metal polishing liquid at the time of using for grinding | polishing, More preferably, it is 4-9, and 5-8 are especially preferable. Within this range, the metal liquid of the present invention exhibits particularly excellent effects.

  The polishing liquid A may contain a chelating agent as necessary in order to reduce adverse effects such as mixed polyvalent metal ions. As a chelating agent, a general-purpose hard water softening agent that is a precipitation inhibitor of calcium or magnesium or an analogous compound thereof can be used, and two or more of these may be used in combination as necessary. The addition amount of the chelating agent may be an amount sufficient to sequester metal ions such as mixed polyvalent metal ions. For example, 0.0003 mol to 0 in 1 L of a metal polishing liquid used for polishing. 0.07 mol is added.

  In the present invention, depending on the adsorptivity and reactivity to the polishing surface, the solubility of the polishing metal, the electrochemical properties of the surface to be polished, the dissociation state of the compound functional group, the stability as a liquid, etc. It is preferable to set the amount, pH, and dispersion medium.

  In addition, it is preferable that the compounding quantity of the thing with the solubility with respect to the solvent in room temperature among the components added at the time of preparation of the concentrated liquid of polishing liquid is less than twice the solubility with respect to the solvent at room temperature. More preferably, it is within 5 times. If this addition amount is twice or more, it becomes difficult to prevent precipitation when the concentrate is cooled to 5 ° C.

[Polishing liquid B (for barrier metal film polishing)]
The polishing liquid B contains an oxidizing agent as an essential component. As the oxidizing agent to be used, the same ones exemplified in the above polishing liquid A can be used. Moreover, the thing similar to the thing illustrated by the above-mentioned polishing liquid A can be used as another component.

  The polishing liquid B of the present invention contains inorganic abrasive grains. Examples of preferable abrasive grains include silica (precipitated silica, fumed silica, colloidal silica, synthetic silica), ceria, alumina, titania, zirconia, germania, manganese oxide, silicon carbide, polystyrene, polyacryl, polyterephthalate, and the like. It is done.

  Among these, particles selected from the group consisting of fumed silica, colloidal silica, synthetic silica, ceria, alumina, titania, zirconia, germania, manganese oxide, and silicon carbide are preferable. In particular, when colloidal silica is used, the remarkable effect of the present invention is obtained, which is preferable.

  As addition amount of an abrasive grain, it is preferable to contain 0.05-20g abrasive grain in 1L of metal polishing liquids at the time of use, and when 0.2-5g abrasive grain is included especially, the effect of this invention is included. Remarkably obtained and preferred. The abrasive grains preferably have an average particle diameter of 5 to 200 nm, and particularly when abrasive grains having an average particle diameter of 20 to 70 nm are used, the effects of the present invention are remarkably obtained, which is preferable.

[Wiring metal raw materials]
In the present invention, the object to be polished is preferably a wiring made of a copper metal and / or a copper alloy in a semiconductor such as LSI, and a copper alloy is particularly preferable. Furthermore, the copper alloy containing silver is preferable among copper alloys. The silver content contained in the copper alloy is preferably 40% by mass or less, particularly 10% by mass or less, more preferably 1% by mass or less, and most preferably in the range of 0.00001 to 0.1% by mass. Exhibits excellent effects.

[Wiring thickness]
In the present invention, the semiconductor to be polished is, for example, a DRAM device system having a half pitch of 0.15 μm or less, particularly 0.10 μm or less, more preferably 0.08 μm or less, while MPU device system is 0.12 μm or less. In particular, an LSI having a wiring of 0.09 μm or less, more preferably 0.07 μm or less is preferable. The polishing liquid of the present invention exhibits particularly excellent effects on these LSIs.

[Barrier metal]
In the present invention, a barrier layer for preventing diffusion of copper is provided between a wiring made of a copper metal and / or a copper alloy of the semiconductor and the interlayer insulating film. As the barrier layer, a low-resistance metal material is preferable, and TiN, TiW, Ta, TaN, W, WN, and Ru are particularly preferable, and Ta and TaN are particularly preferable.

(Chemical mechanical polishing method)
The chemical mechanical polishing method of the present invention is a method for polishing a semiconductor integrated circuit having a barrier metal film and a conductor film thereon, wherein the barrier metal film and the conductor film are continuously formed on one polishing pad. Then, the conductor film is polished with the polishing liquid A described above, and the barrier metal film is polished with the polishing liquid B described above. Hereinafter, the term “polishing liquid” means each of the polishing liquid A and the polishing liquid B.

  The polishing liquid is a concentrated liquid that is diluted by adding water when used, or mixed in the form of an aqueous solution described in the next section for each component, and diluted by adding water as necessary. In some cases, it may be used as a working solution or prepared as a working solution. The polishing method using the polishing liquid A and the polishing liquid B can be applied to both cases, and the polishing liquid is supplied to the polishing pad on the polishing surface plate and brought into contact with the surface to be polished to thereby connect the surface to be polished and the polishing pad. This is a polishing method in which polishing is performed by relative movement.

  As an apparatus for polishing, there is a general polishing apparatus having a polishing surface plate with a holder for holding a semiconductor substrate having a surface to be polished and a polishing pad attached (a motor etc. capable of changing the number of rotations is attached). Can be used. As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used, and there is no particular limitation. The pressure applied to the polishing pad of the semiconductor substrate having the surface to be polished (film to be polished) is preferably 0.68 to 34.5 KPa, which satisfies the uniformity of the polishing surface within the wafer surface and the flatness of the pattern. Therefore, it is more preferable that it is 3.40-20.7 KPa.

  During polishing, a polishing liquid is continuously supplied to the polishing pad with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with polishing liquid. The semiconductor substrate after polishing is thoroughly washed in running water, and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like. In the polishing method of the present invention, the aqueous solution to be diluted is the same as the aqueous solution described below. The aqueous solution is water containing at least one of an oxidizing agent, an acid, an additive, and a surfactant in advance, and the total amount of the components contained in the aqueous solution and the components of the polishing liquid to be diluted is the polishing liquid. Use it as a component when polishing. When diluted with an aqueous solution and used, components that are difficult to dissolve can be blended in the form of an aqueous solution, and a more concentrated polishing liquid can be prepared.

  As a method of diluting by adding water or an aqueous solution to the concentrated polishing liquid, the pipe for supplying the concentrated polishing liquid and the pipe for supplying the water or the aqueous solution are joined together and mixed, and mixed and diluted. There is a method of supplying a polishing pad to a polishing pad. Mixing is a method in which liquids collide with each other through a narrow passage under pressure, a method in which a filling such as a glass tube is filled in a pipe, and the flow of liquid is repeatedly separated and merged. Conventional methods such as a method of providing blades that rotate in the above can be employed.

  The supply rate of the polishing liquid is preferably 10 to 1000 ml / min, and more preferably 170 to 800 ml / min in order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern.

  As a method of diluting the concentrated polishing liquid with water or an aqueous solution and polishing, a pipe for supplying the polishing liquid and a pipe for supplying water or an aqueous solution are provided independently, and a predetermined amount of liquid is supplied from each to the polishing pad. In this method, the polishing pad and the surface to be polished are mixed while being mixed by relative movement. Alternatively, there is a method in which a predetermined amount of concentrated polishing liquid and water or an aqueous solution are mixed in one container, and then the mixed polishing liquid is supplied to a polishing pad for polishing.

  According to another aspect of the present invention, the chemical mechanical polishing method divides the components to be contained in the polishing liquid into at least two constituent components and, when using them, dilutes by adding water or an aqueous solution to polish the polishing composition. This is a method in which polishing is performed by supplying a polishing pad on a board and bringing the surface to be polished into contact with the surface to be polished and moving the surface to be polished and the polishing pad relative to each other. For example, an oxidizing agent is one component (A), an acid, an additive, a surfactant, and water are one component (B), and when they are used, the component (A) The component (B) is diluted before use.

  Further, an additive having low solubility is divided into two components (A) and (B), and an oxidizing agent, an additive (a component other than abrasive grains, an oxidizing agent, an acid, and a surfactant) and a surfactant are combined into one component. Constituent component (A), acid, additive, surfactant and water are one constituent component (B), and when using them, water or an aqueous solution is added to add constituent component (A) and constituent component (B). Dilute and use. In the case of this example, three pipes for supplying the component (A), the component (B), and water or an aqueous solution are required, and dilution mixing is performed on one pipe that supplies the three pads to the polishing pad. There is a method of combining and mixing in the pipe. In this case, it is also possible to combine two pipes and then connect another pipe.

  For example, it is a method in which a component containing an additive that is difficult to dissolve is mixed with another component, a mixing path is lengthened to ensure a dissolution time, and then a pipe for water or an aqueous solution is further combined. Other mixing methods are as described above, in which the three pipes are each guided directly to the polishing pad and mixed by the relative movement of the polishing pad and the surface to be polished, and the three components are mixed in one container. The diluted polishing liquid is supplied to the polishing pad. In the above polishing method, one constituent component containing an oxidizing agent is made 40 ° C. or lower, the other constituent components are heated in the range of room temperature to 100 ° C., and one constituent component and another constituent component or water or an aqueous solution When the mixture is diluted and used, it can be adjusted to 40 ° C. or lower after mixing. Since the solubility increases when the temperature is high, this is a preferable method for increasing the solubility of the raw material having a low solubility of the polishing liquid.

  A raw material in which other components not containing an oxidizing agent are heated and dissolved in the range of room temperature to 100 ° C. is precipitated in the solution when the temperature is lowered. It is necessary to dissolve what is deposited by heating. For this, a means for feeding a heated component solution and a means for stirring the liquid containing the precipitate, feeding the liquid, and heating and dissolving the pipe can be employed. When the temperature of one component containing an oxidant is increased to 40 ° C. or higher, the oxidant may be decomposed. Therefore, the heated component and the oxidation for cooling the heated component When mixed with one component containing an agent, the temperature is set to 40 ° C. or lower.

  In the present invention, as described above, the components of the polishing liquid may be divided into two or more parts and supplied to the polishing surface. In this case, it is preferable to divide and supply the component containing an oxide and the component containing an acid. Alternatively, the polishing liquid may be a concentrated liquid, and diluted water may be separately supplied to the polishing surface.

〔pad〕
The polishing pad (polishing pad) may be a non-foamed structure pad or a foamed structure pad. The former uses a hard synthetic resin bulk material like a plastic plate for a pad. Further, the latter further includes three types of a closed foam (dry foam system), a continuous foam (wet foam system), and a two-layer composite (laminated system), and a two-layer composite (laminated system) is particularly preferable. Foaming may be uniform or non-uniform.

  Further, it may contain abrasive grains (for example, ceria, silica, alumina, resin, etc.) used for polishing. In addition, the hardness may be either soft or hard, and either may be used. In the laminated system, it is preferable to use a different hardness for each layer. The material is preferably non-woven fabric, artificial leather, polyamide, polyurethane, polyester, polycarbonate or the like. In addition, the surface contacting the polishing surface may be subjected to processing such as lattice grooves / holes / concentric grooves / helical grooves.

[Conditioning process]
In the present invention, it is preferable to include a conditioning process for removing solid abrasive grains and polishing debris deposited on the polishing pad. By providing this step, polishing stability can be exhibited.

  In the conditioning of the polishing pad, the pressing load against the pad of the conditioner is preferably 60 hPa or more, and more preferably 70 to 500 hPa. By being 60 hPa or more, it is possible to suppress a reduction in polishing rate and generation of scratches.

[Wafer]
The target wafer to be subjected to CMP with the polishing liquid of the present invention preferably has a diameter of 200 mm or more, particularly preferably 300 mm or more. The effect of the present invention is remarkably exhibited when the thickness is 300 mm or more.

  Although the apparatus which can implement the polishing method of the present invention is not particularly limited, Mirror Mesa CMP, Reflexion CMP (Applied Materials), FREX200, FREX300 (Ebara Manufacturing), NPS3301, NPS2301 (Nikon), A-FP-310A, A -FP-210A (Tokyo Seimitsu), 2300 TERES (ram research), Momentum (novelas), etc. can be mentioned.

  Hereinafter, the present invention will be described by way of examples. The present invention is not limited to these examples.

(Preparation of polishing liquid)
<Cu-CMP polishing liquid>
Abrasive (Colloidal silica) ... Concentrations listed in Table 1 below Hydrogen peroxide (oxidant) ... 90 g / L
DL-malic acid 2g / L
Benzotriazole 3 g / L (in terms of solid content)
Ammonium polyacrylate ... 5g / L
pH (adjusted with ammonia water and nitric acid) 4.0

  A polishing liquid A was prepared by mixing the materials shown above and adding pure water so that the material had the concentration shown above to make the total volume 1000 mL.

<Barrier metal polishing liquid>
Abrasive (Colloidal Silica) ... Concentrations listed in Table 1 below (solid content conversion)
Hydrogen peroxide (oxidant) ... 3g / L
Oxalic acid dihydrate 2g / L
Benzotriazole: 1 g / L (in terms of solid content)
pH (adjusted with aqueous ammonia and nitric acid) ... 3.0
A polishing liquid B was prepared by mixing the materials shown above and adding pure water so that the material had the concentration shown above to make the total amount 1000 mL.

  Polishing liquid A (polishing liquid for conductive film) and polishing liquid B (polishing liquid for barrier metal) were combined as shown in Table 1 to give Examples 1 to 11 and Comparative Examples 1 to 8, and the following polishing tests were performed.

(Polishing test)
An apparatus “FREX-300” manufactured by Ebara Corporation was used as a polishing apparatus, and polishing was performed under the following conditions. The results are shown in Table 1 below.

<Polishing conditions>
Table rotation speed: 78 rpm
Head rotation speed: 79 rpm
Polishing pressure: 210 hPa
Polishing pad: Part number IC-1400 (K-grv) + (A21) manufactured by Rodel Nitta Co., Ltd.
Slurry supply rate: 300 ml / min

<Conditioning conditions>
Conditioner: CMP-MC100A (Asahi Diamond)
Table rotation speed: 20 rpm
Conditioner rotation speed: 17rpm
Pressing pressure: 150 hPa
Pressing time: 30 seconds

<Conditioner>
A substrate in which an abrasive layer in which diamond abrasive grains are fixed with a metallic binder phase such as nickel is formed on the surface of a substantially disc-shaped substrate made of stainless steel. Diamond particles having a size of # 80 to # 325 were used. Here, # (count) representing the size of the particle represents the number of meshes per inch, and refers to the particle size passing through a mesh of this size.

<Polishing speed>
For 81 locations on the wafer surface, the thickness of the metal film before and after CMP was converted from the electrical resistance value, and the average polishing rate was determined. The results are shown in Table 1 below. The measurement conditions are as follows.

Wafer: 12-inch Cu blanket wafer (Cu film thickness 1500 nm / Ta film thickness 25 nm / oxide film thickness 200 nm)
Measuring device: DC 4 probe type sheet resistance measuring instrument VR-120 (Hitachi Kokusai Electric)
Polishing rate (nm / min) = (thickness of copper film before polishing−thickness of copper film after polishing) / polishing time

<Dishing>
A commercially available pattern wafer was polished, and the dishing amount of a 100 μm wiring portion on the wafer was measured. The results are shown in Table 1 below. The measurement conditions are as follows.

Object to be polished: 754 mask pattern wafer (atdf)
Measuring device: Contact type step measuring device Dektak V320Si (Veeco)
The polishing time was a time corresponding to 130% when the time when the barrier surface was exposed was 100% (30% overpolishing).

  In the embodiment, as shown in FIG. 2, after polishing the conductor film by supplying the Cu-CMP polishing liquid to one table, the barrier CMP polishing liquid is continuously supplied to polish the barrier metal film. The surface to be polished was cleaned with water polish.

  In the comparative example, as shown in FIG. 3, after supplying the Cu-CMP polishing liquid to the first table and polishing the conductor film, the surface is subsequently cleaned with water polish, and the next second After transporting to the table, the barrier metal film was polished by supplying a barrier polishing liquid, and then the surface to be polished was cleaned with water polish. In the comparative example, the mode in which the conductor film and the barrier film are polished separately by two tables is shown, but the present invention is not limited to this, for example, when polishing by three or more tables.

<Measurement of scratches>
Scratch evaluation was performed by polishing the exposed oxide film surface on the surface using a wafer surface defect inspection apparatus SP1-TBI manufactured by KLA Tencor and counting 0.2 μm or more scratches on the surface after polishing as described above. The results are shown in Table 1 below.

  From the results shown in Table 1, it is confirmed that all of the polishing methods of the examples are superior in processing efficiency and can continuously polish the conductor film and the barrier film with the same pad as compared with the comparative example. did it.

It is process drawing explaining the flow of the method of forming a buried copper wiring. It is a conceptual diagram explaining the grinding | polishing process of an Example. It is a conceptual diagram explaining the grinding | polishing process of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Lower wiring layer 2 ... Silicon nitride film 3 ... Insulating film 4 ... Barrier metal film 5 ... Copper film

Claims (4)

A chemical mechanical polishing method for polishing a semiconductor integrated circuit having a barrier metal film and a conductor film thereon,
The barrier metal film and the conductive film are continuously polished on a single polishing pad, and the polishing liquid A for polishing the conductive film is a polishing liquid that contains an oxidizing agent and does not contain inorganic abrasive grains, A chemical mechanical polishing method, wherein the polishing liquid B for polishing the barrier metal film is a polishing liquid containing an oxidizing agent and inorganic abrasive grains.   Furthermore, the pressing load with respect to the pad of the conditioner used for the said conditioning process is 60 hPa or more including the conditioning process which removes the solid abrasive grain and polishing waste deposited on the said polishing pad. Chemical mechanical polishing method.   The inorganic abrasive grains of the polishing liquid B are particles selected from the group consisting of fumed silica, colloidal silica, synthetic silica, ceria, alumina, titania, zirconia, germania, manganese oxide, and silicon carbide. The chemical mechanical polishing method according to claim 1.   Each of the oxidizing agent of the polishing liquid A and the oxidizing agent of the polishing liquid B is hydrogen peroxide, peroxide, nitrate, iodate, periodate, hypochlorite, chlorite, chloric acid. A salt, a perchlorate salt, a persulfate salt, a dichromate salt, a permanganate salt, ozone water, a silver (II) salt and an iron (III) salt. The chemical mechanical polishing method according to claim 1, wherein

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