JP2015029001A - Polishing liquid for cmp, and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid for CMP by which the occurrence of an organic residue can be reduced.SOLUTION: A polishing liquid for CMP comprises (A) benzotriazole, (B) a citric acid, the amount of which is 3.0 or more times that of the benzotriazole, and (C) an oxidant.

Description

  Embodiments described herein relate generally to a polishing liquid for CMP and a polishing method.

  In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (hereinafter referred to as “LSI”). One of them is a chemical mechanical polishing (hereinafter referred to as “CMP”) method. The CMP method is a technique frequently used in planarization of an interlayer insulating film, formation of a metal plug, formation of a buried wiring, etc. in an LSI manufacturing process, particularly in a multilayer wiring forming process.

  Recently, in order to improve the performance of LSIs, attempts have been made to use copper or copper alloys among metals as conductive materials used in wiring portions. However, it has been difficult to finely process copper or a copper alloy by a dry etching method used for forming a conventional aluminum alloy wiring.

  Therefore, a so-called damascene method is mainly employed as a technique for forming the wiring. In the damascene method, first, a conductive material such as copper or a copper alloy is deposited on an interlayer insulating film in which concave portions (groove portions) and convex portions (protruded portions) are formed in advance on the surface, and the conductive material is embedded in the concave portions. . Next, the conductive material (other than the concave portion) deposited on the convex portion is removed by CMP to form a buried wiring made of the conductive material.

  In general, a barrier conductor layer (hereinafter referred to as “barrier layer”) is formed under the conductive material to prevent diffusion of the conductive material into the interlayer insulating film and improve adhesion. Yes. The barrier layer is a layer made of a conductor such as tantalum, a tantalum alloy, or tantalum nitride.

  FIG. 1 is a schematic cross-sectional view showing an example of a wiring forming process by a damascene method. As shown in FIG. 1A, the substrate 100 before polishing is configured to follow the interlayer insulating film 1 having unevenness formed by recesses and protrusions formed on the surface, and the surface unevenness of the interlayer insulating film 1. And a conductive material portion 3 deposited so as to fill the unevenness.

  For the barrier layer 2, a conductor having a higher hardness than that of a conductive material is usually used. Therefore, even if a polishing material for a conductive substance is combined in the polishing slurry for CMP, a sufficient polishing rate cannot be obtained for the barrier layer, and the flatness of the surface to be polished may deteriorate. Therefore, in the wiring formation by the damascene method, a polishing method having a two-step polishing process generally including a first polishing process for polishing the conductive material portion 3 and a second polishing process for polishing the barrier layer 2 is generally used. Used.

  That is, first, as shown in FIG. 1B, in the first polishing step, the conductive material portion is exposed with the polishing liquid for the conductive material until the barrier layer 2 on the convex portion of the interlayer insulating film 1 is exposed. 3 is polished. Next, as shown in FIG. 1C, as a second polishing step, the barrier layer 2 is polished with a polishing liquid for the barrier layer until the protrusions of the interlayer insulating film 1 are exposed, and the substrate after polishing is polished. Get 200.

  By the way, as a method for increasing the polishing rate by CMP, it is effective to add a metal dissolving agent to the polishing liquid for CMP. However, if a metal solubilizer is used, the etching of the conductive material portion 3 progresses, and a phenomenon that the central portion of the surface of the embedded conductive material portion becomes depressed like a dish after polishing (dishing) occurs, resulting in flattening. The effect may be impaired.

  In order to prevent this, a method using a polishing slurry for CMP containing benzotriazole (hereinafter referred to as “BTA”) as a metal anticorrosive has been proposed (see, for example, Patent Document 1). In order to further improve the flatness, a polishing slurry for CMP using a specific imidazole, pyrazole, thiazole, triazole or guanidine in combination with BTA has been proposed (see, for example, Patent Document 2). ).

Japanese Patent Laid-Open No. 08-083780 JP 2008-270826 A

  BTA used as a metal anticorrosive is known to form an insoluble metal complex by reaction with a metal, particularly copper. The insoluble metal complex remains as an organic residue on the embedded wiring (metal wiring) even after the cleaning process, which may affect the subsequent process. For example, there are problems such as inaccurate pattern layout in the upper layer and inducing a short circuit between metal wirings.

  In recent years, the scaling of wiring has further progressed due to the LSI having a multilayer wiring structure. Such LSIs are required to reduce organic residues in order to deteriorate device characteristics even with a small amount of organic residues.

  Embodiments of the present invention are intended to solve the above-described problems, and provide a polishing liquid for CMP that can reduce the generation of organic residues, and also provide a polishing method that can reduce the generation of organic residues. With the goal.

  Various embodiments of the present invention use a polishing slurry for CMP containing 3.0 times or more of citric acid with respect to BTA, thereby forming a complex containing a conductive substance and BTA (hereinafter referred to as a “conductive substance complex”). ")") Was found to be water-soluble.

  That is, the present invention includes an embodiment relating to a polishing slurry for CMP containing (A) BTA, (B) citric acid of 3.0 times or more with respect to BTA, and (C) an oxidizing agent.

  (A) As for content of BTA, 0.01-2 mass parts is preferable with respect to 100 mass parts of polishing liquid for CMP.

  The content of (B) citric acid is preferably 8.0 parts by mass or less with respect to 100 parts by mass of the polishing slurry for CMP.

  (C) As the oxidizing agent, for example, at least one selected from the group consisting of hydrogen peroxide, periodate, persulfate, hypochlorite, and ozone can be used.

  In one embodiment, the CMP polishing liquid may further contain (D) abrasive grains. (D) The abrasive preferably contains at least one selected from the group consisting of silica particles, alumina particles, ceria particles, titania particles, zirconia particles, germania particles, and modified products thereof.

  In one embodiment, the CMP polishing liquid may further contain (E) a metal dissolving agent. (E) The metal solubilizer preferably contains at least one selected from the group consisting of organic acids, organic acid esters, ammonium salts of organic acids, inorganic acids, and ammonium salts of inorganic acids.

  In one embodiment, the CMP polishing liquid may further contain (F) a water-soluble polymer.

  Furthermore, in one embodiment, the polishing slurry for CMP may further contain (G) an organic solvent. (G) The organic solvent contains at least one selected from the group consisting of carbonate esters, lactones, glycols, alcohols, ethers, ketones, esters, amides, sulfolanes, and derivatives of glycols. It is preferable.

  The present invention also includes an embodiment relating to a polishing method for polishing an object to be polished using the CMP polishing liquid.

  In one embodiment, a polishing method includes an interlayer insulating film having a ridge and a groove on a surface, a barrier layer that covers the interlayer insulating film along the surface, and a conductive material portion that covers the barrier layer, A first polishing step of polishing the conductive material portion of the substrate having a surface to expose a barrier layer located on the raised portion of the interlayer insulating film, and the CMP of the barrier layer exposed by the first polishing step And a second polishing step in which the raised portions of the interlayer insulating film are exposed by polishing with a polishing slurry.

  The conductive material portion preferably contains at least one selected from the group consisting of copper, copper alloys, copper oxides, and copper alloy oxides. The barrier layer preferably contains at least one selected from the group consisting of tantalum, tantalum compounds, titanium, titanium compounds, tungsten, tungsten compounds, ruthenium, ruthenium compounds, cobalt, and cobalt compounds.

  By using the CMP polishing liquid according to the embodiment of the present invention, the generation of organic residues can be reduced. Moreover, generation | occurrence | production of an organic residue can be reduced with the grinding | polishing method which is embodiment of this invention.

FIG. 1 is a schematic cross-sectional view showing an example of a wiring forming process by a damascene method.

Hereinafter, embodiments of the present invention will be described in detail.
[CMP polishing liquid]
The CMP polishing liquid according to the embodiment of the present invention contains at least (A) BTA, (B) 3.0 times or more citric acid with respect to BTA, and (C) an oxidizing agent.

  The CMP polishing liquid of this embodiment can make the complex of the conductive substance water-soluble. The mechanism by which the complex of the conductive substance becomes water-soluble when the CMP polishing liquid of this embodiment is used is estimated as follows, for example.

  That is, conventionally, a complex composed of a conductive substance (metal) and BTA shows insolubility because the hydrophobic benzene ring is located outside the complex when the nitrogen atom of BTA binds to the metal. This is considered to be caused by the fact that Metals have electrons in the d orbital, but the electrons themselves are not enough to become closed nuclei. Therefore, the metal attracts electrons from the lone pair of nitrogen atoms in BTA, forms a closed nucleus state in a form that satisfies the 18-electron rule, and stabilizes. That is, BTA binds to the metal so that the metal is covered with the nitrogen atom inside, so that a benzene ring exists outside the metal complex. In addition, there is a possibility that the complexes are bonded to each other by the interaction between the benzene rings, and a metal complex having a large molecular weight is formed. As a result, the metal complex becomes insoluble and appears as an organic residue on the metal wiring after CMP.

  In contrast, the CMP polishing liquid of this embodiment contains citric acid in excess of BTA, so that a metal complex is formed by metal, BTA, and citric acid. At this time, water-soluble citric acid is appropriately coordinated with the metal to form a closed nucleus, and as a result, the affinity of the metal complex for water increases. Furthermore, when a metal complex is formed with a metal, BTA, and citric acid, the coupling | bonding of complexes is suppressed and the molecular weight of a metal complex is suppressed small. Although the detailed reaction mechanism is not clear, it is presumed that when the metal complex is water-soluble, the metal complex is removed by cleaning the substrate after CMP, and the organic residue on the metal wiring is reduced.

[(A) component: BTA]
The polishing liquid for CMP of this embodiment contains BTA. BTA acts as a metal anticorrosive, and the inclusion of BTA can suppress etching and roughening of the surface to be polished.

  The content of BTA is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the CMP polishing liquid from the viewpoint of suppression of etching of the metal wiring and suppression of roughness of the surface to be polished, and more preferably 0. 02 parts by mass or more, more preferably 0.05 parts by mass or more. Further, the content of BTA is preferably 2 parts by mass or less, more preferably 1 part by mass or less, still more preferably 0.5 parts by mass or less, particularly preferably from the viewpoint of suppressing a reduction in polishing rate. Is 0.3 parts by mass or less.

[(B) component: citric acid of 3.0 times or more relative to BTA]
The CMP polishing liquid of the present embodiment contains citric acid that is 3.0 times or more the amount of BTA in order to reduce the generation of organic residues. “3.0 times or more” means that the mass ratio is 3.0 or more.

  The citric acid content is preferably 3.5 times or more, and more preferably 3.8 times or more. The upper limit of the citric acid content is not particularly limited, but is generally preferably 100 times or less, more preferably 50 times or less, and still more preferably 10 times or less the amount of BTA.

  In addition, the content of citric acid is preferably 8.0 parts by mass or less, more preferably 4.0 parts by mass or less, with respect to 100 parts by mass of the polishing slurry for CMP, from the viewpoint of suppressing etching of the conductive substance part. 2.0 parts by mass or less is more preferable, and 1.0 part by mass or less is particularly preferable.

[(C) component: oxidizing agent]
The CMP polishing liquid of this embodiment contains an oxidizing agent. The oxidizing agent is not particularly limited, and can be selected from compounds having an oxidizing action on metals, such as hydrogen peroxide, periodate, persulfate (peroxosulfate), hypochlorite, Examples include ozone, and among them, hydrogen peroxide is preferable. Examples of the salt include salts with alkali metals such as sodium and potassium, salts with alkaline earth metals such as magnesium and calcium, and ammonium salts. These oxidizing agents are preferable from the viewpoint of obtaining a good polishing rate for the barrier layer while suppressing the occurrence of roughness of the surface to be polished.

  The oxidizing agent can be used as an aqueous solution. Moreover, an oxidizing agent can be used individually by 1 type or in mixture of 2 or more types.

  The content of the oxidizing agent is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more with respect to 100 parts by mass of the CMP polishing liquid, from the viewpoint of oxidizing the metal and improving the polishing rate. 0.05 mass part or more is still more preferable, and 0.1 mass part or more is especially preferable. Further, the content of the oxidizing agent is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 15 parts by mass or less from the viewpoint of suppressing the roughness of the surface to be polished. In particular, the content of the oxidizing agent is particularly preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and very preferably 3 parts by mass or less from the viewpoint of suppressing corrosion of the conductive substance part.

[(D) component: abrasive]
The CMP polishing liquid of this embodiment may further contain abrasive grains. By containing the abrasive grains, the mechanical polishing power is improved and the polishing rate tends to be improved. The abrasive grains are not particularly limited, and examples thereof include silica particles, alumina particles, ceria particles, titania particles, zirconia particles, germania particles, and modified products thereof. An abrasive grain can be used individually by 1 type or in mixture of 2 or more types.

  Examples of the modified product include those obtained by modifying the surface of particles such as silica particles, alumina particles, ceria particles, titania particles, zirconia particles, and germania particles with an alkyl group. The method for modifying the surface of the particle with an alkyl group is not particularly limited, and examples thereof include a method of reacting a hydroxyl group present on the surface of the particle with an alkoxysilane having an alkyl group. The alkoxysilane having an alkyl group is not particularly limited, but monomethyltrimethoxysilane, dimethyldimethoxysilane, trimethylmonomethoxysilane, monoethyltrimethoxysilane, diethyldimethoxysilane, triethylmonomethoxysilane, monomethyltriethoxysilane, dimethyl Examples include diethoxysilane and trimethylmonoethoxysilane. There is no restriction | limiting in particular as a reaction method, For example, particle | grains and alkoxysilane are made to react in a dispersion liquid or polishing liquid at room temperature or under heating.

  Among the abrasive grains, silica particles or alumina particles are preferable in that they are excellent in dispersion stability in a polishing liquid for CMP and the number of occurrence of polishing scratches (scratches) generated by CMP is reduced, and colloidal silica or colloidal alumina. Is more preferable.

  The average particle size of the abrasive grains is preferably 10 nm or more, more preferably 20 nm or more, and further preferably 30 nm or more from the viewpoint of the polishing rate. The average particle size of the abrasive grains is preferably 200 nm or less, more preferably 150 nm or less, and still more preferably 120 nm or less, from the viewpoint of reducing polishing flaws.

The average particle diameter of the abrasive grains can be measured with a light diffraction / scattering particle size distribution meter (for example, COULTER Electronics, trade name: COULTER N4SD). For example, the measurement conditions of a light diffraction / scattering particle size distribution meter are: measurement temperature 20 ° C., solvent refractive index 1.333 (corresponding to the refractive index of water), particle refractive index Unknown (setting), solvent viscosity 1.005 mPa · s ( Equivalent to the viscosity of water), Run Time 200 sec, laser incident angle 90 °. Further, Intensity (scattering intensity, corresponds to turbidity) is to fall in the range of ^{5 × 10 4 ~4 × 10 5} , is higher than 4 × 10 ⁵ is measured by diluting with water.

  When the abrasive grains are contained, the content thereof is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, with respect to 100 parts by mass of the CMP polishing liquid, from the viewpoint of improving the polishing rate. More preferably, it is 0.05 mass part or more. The content of abrasive grains is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less, from the viewpoint of suppressing the generation of polishing flaws.

[(E) component: metal dissolving agent]
The CMP polishing liquid of this embodiment may further contain a metal dissolving agent. (B) Citric acid can also be a metal solubilizing agent, but a more practical polishing rate can be achieved by including a further metal solubilizing agent. In addition, the metal dissolving agent which is (E) component shall not contain a citric acid.

  The metal solubilizer is not particularly limited, and examples thereof include organic acids, organic acid esters, ammonium salts of organic acids, inorganic acids, ammonium salts of inorganic acids, and the like. For example, formic acid, acetic acid, propionic acid, butyric acid, Herbic 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-ethylhexane Acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, p-toluenesulfonic acid, aspartic acid , Organic acids such as glutamic acid, glycine and histidine; these organic acid esters and ammonium salts of these organic acids; hydrochloric acid, sulfuric acid, nitric acid, chlorine Inorganic acids such as acid, ammonium chloride, ammonium persulfate, ammonium nitrate, and ammonium salts of inorganic acids such as ammonium chromate acid. Among these, formic acid, malonic acid, malic acid, tartaric acid, salicylic acid, adipic acid and the like are preferable in that the etching rate can be effectively suppressed while maintaining a practical polishing rate. A metal dissolving agent can be used individually by 1 type or in mixture of 2 or more types.

  When the metal solubilizer is contained, the content thereof is preferably 0.001 part by mass or more with respect to 100 parts by mass of the polishing slurry for CMP from the viewpoint of improving the polishing rate of the conductive substance part and the barrier layer. Preferably it is 0.01 mass part or more, More preferably, it is 0.05 mass part or more. In addition, the content of the metal solubilizer is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, particularly preferably from the viewpoint of suppressing etching and suppressing roughness of the surface to be polished. It is 3 parts by mass or less, and very preferably 1 part by mass or less.

[(F) component: water-soluble polymer]
The CMP polishing liquid of this embodiment may further contain (F) a water-soluble polymer. Here, “water-soluble” means that 0.01 g or more is dissolved in 100 g of water at 25 ° C. The water-soluble polymer can be preferably used from the viewpoint that the occurrence of roughness of the surface to be polished can be effectively suppressed.

  The water-soluble polymer is not particularly limited, and examples thereof include polycarboxylic acids and derivatives thereof, polysaccharides, and vinyl polymers. Polycarboxylic acid derivatives include polycarboxylic acid salts, polycarboxylic acid esters, polycarboxylic acid amides, and the like.

Examples of water-soluble polymers include:
Polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, polyglyoxyl Acid, polymethacrylic acid ammonium salt, polymethacrylic acid sodium salt, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, polyamic acid ammonium salt, polyamic acid sodium salt, polyaspartic acid ester, polyglutamic acid ester, polymethacrylic acid ester, Polycarboxylic acids such as polyamic acid ester, polymaleic acid ester, polyfumaric acid ester, polyacrylic acid ester and derivatives thereof;
Polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan, pullulan;
Examples thereof include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and polyacrolein.
One type of water-soluble polymer can be used alone, or two or more types can be mixed and used.

  The weight average molecular weight (Mw) of the water-soluble polymer is preferably 500 or more, more preferably 1500 or more, and still more preferably 5000 or more, from the viewpoint of obtaining a high polishing rate. The upper limit of the weight average molecular weight of the water-soluble polymer is not particularly limited, but is preferably 5 million or less from the viewpoint of solubility. More preferably, it is 1,000,000 or less, More preferably, it is 200,000 or less, Especially preferably, it is 100,000 or less, Very preferably, it is 50,000 or less, Very preferably, it is 20,000 or less. The weight average molecular weight of the water-soluble polymer can be measured by gel permeation chromatography.

When the water-soluble polymer is other than “polycarboxylic acid and derivatives thereof”, the weight average molecular weight can be measured, for example, by measuring the following conditions and reading the value obtained as “Mw”.
Sample: 10 μL
Standard polystyrene: Standard polystyrene manufactured by Tosoh Corporation (molecular weight: 190000, 17900, 9100, 2980, 578, 474, 370, 266)
Detector: manufactured by Hitachi, Ltd., RI-monitor, trade name “L-3000”
Integrator: Hitachi, Ltd., GPC integrator, product name “D-2200”
Pump: Hitachi, Ltd., trade name “L-6000”
Degassing device: Showa Denko Co., Ltd., trade name "Shodex DEGAS"
Column: Hitachi Chemical Co., Ltd., trade names “GL-R440”, “GL-R430”, “GL-R420” connected in this order and used as eluent: tetrahydrofuran (THF)
Measurement temperature: 23 ° C
Flow rate: 1.75 mL / min Measurement time: 45 minutes

When the water-soluble polymer is “polycarboxylic acid and derivatives thereof”, the weight average molecular weight can be measured, for example, by measuring under the following conditions and reading the value obtained as “Mw”.
Equipment used (detector): Hitachi, Ltd., L-3300 differential refractometer for liquid chromatograph Pump: Hitachi, Ltd., L-7100 type liquid chromatograph Data processing: Hitachi, Ltd. D-2520 type GPC integrator column: Showa Denko KK, Shodex Asahipak GF-710HQ, inner diameter 7.6 mm × 300 mm
Eluent: 50 mM Na ₂ HPO ₄ aqueous solution / acetonitrile = 90/10 (v / v)
Flow rate: 0.6 mL / min Sample: Adjust with a solution having the same composition as the eluent so that the resin concentration is 2%, and filter with a 0.45 μm polytetrafluoroethylene filter Injection volume: 0.4 μL
Calibration standard material: Polymer Laboratories, low molecular weight sodium polyacrylate

  The content of the water-soluble polymer is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, and more preferably 0.005 parts by mass or more with respect to 100 parts by mass of the CMP polishing liquid, from the viewpoint of suppressing the roughness of the surface to be polished. Preferably it is 0.01 mass part or more. The content of the water-soluble polymer is preferably 15 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 1 part by mass or less, particularly from the viewpoint of keeping the CMP polishing liquid low in viscosity and easy to handle. Preferably it is 0.5 mass part or less.

[(G) component: organic solvent]
The polishing slurry for CMP of this embodiment may further contain (G) an organic solvent. Although there is no restriction | limiting in particular as an organic solvent, A water-soluble organic solvent is preferable. Here, “water-soluble” means that 0.1 g or more dissolves in 100 g of water at 25 ° C. The use of an organic solvent tends to improve the wettability of the polishing liquid for CMP to the surface to be polished, particularly the interlayer insulating film, and improve the polishing rate.

  Examples of the organic solvent include carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; lactones such as butyrolactone and propiolactone; ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, Glycols such as triethylene glycol, tripropylene glycol, polyethylene glycol; alcohols such as methanol, ethanol, propanol, n-butanol, n-pentanol, n-hexanol, isopropanol, 3-methoxy-3-methyl-1-butanol (Monoalcohols); ethers such as tetrahydrofuran, dioxane, dimethoxyethane (excluding derivatives of glycols); Acetone, ketones such as methyl ethyl ketone, ethyl acetate, (excluding such carbonic esters and lactones) esters such as ethyl lactate; dimethylformamide, amides such as N- methyl pyrrolidone; and sulfolane such as sulfolane.

  The organic solvent may be a derivative of glycols. For example, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, diethylene glycol monoethyl ether , Dipropylene glycol monoethyl ether, triethylene glycol monoethyl ether, tripropylene glycol monoethyl ether, ethylene glycol monopropyl ether, propylene glycol monopropyl ether, diethylene glycol monopropyl ether, dipropylene glycol monopropyl ether Glycol monoethers such as triethylene glycol monopropyl ether, tripropylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol monobutyl ether, triethylene glycol monobutyl ether, tripropylene glycol monobutyl ether Class: ethylene glycol dimethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, triethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol diethyl ether Ter, diethylene glycol diethyl ether, dipropylene glycol diethyl ether, triethylene glycol diethyl ether, tripropylene glycol diethyl ether, ethylene glycol dipropyl ether, propylene glycol dipropyl ether, diethylene glycol dipropyl ether, dipropylene glycol dipropyl ether, triethylene Glycol diethers such as glycol dipropyl ether, tripropylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dibutyl ether, diethylene glycol dibutyl ether, dipropylene glycol dibutyl ether, triethylene glycol dibutyl ether, tripropylene glycol dibutyl ether And glycol ether esters such as ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, and propylene glycol monomethyl ether acetate.

  Among these, carbonate esters, glycols, alcohols, and derivatives of glycols are preferable, and alcohols are more preferable. An organic solvent can be used individually by 1 type or in mixture of 2 or more types.

  In the case of containing an organic solvent, the content is preferably 0.1 parts by mass or more with respect to 100 parts by mass of the CMP polishing liquid, from the viewpoint of improving the wettability of the CMP polishing liquid to the surface to be polished. Preferably it is 0.5 mass part or more, More preferably, it is 0.8 mass part or more. In addition, the content of the organic solvent is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 10 parts by mass with respect to 100 parts by mass of the polishing slurry for CMP from the viewpoint of suppressing a decrease in dispersibility. Or less, particularly preferably 5 parts by mass or less.

[(H) component: water]
The CMP polishing liquid of this embodiment may contain water. The water content may be the balance of the above-mentioned components.

[(I) component: metal anticorrosive]
The CMP polishing liquid of this embodiment may further contain a water-soluble metal anticorrosive. Here, “water-soluble” means that 0.01 g or more is dissolved in 100 g of water at 25 ° C. Examples of water-soluble metal anticorrosives include triazole compounds, pyridine compounds, pyrazole compounds, pyrimidine compounds, imidazole compounds, guanidine compounds, thiazole compounds, tetrazole compounds, and triazine compounds. A metal anticorrosive can be used individually by 1 type or in mixture of 2 or more types. Here, “compound” is a general term for compounds having the skeleton, and for example, a triazole compound means a compound having a triazole skeleton. In addition, BTA is not contained in the metal anticorrosive which is (I) component.

[PH]
The pH of the CMP polishing liquid of this embodiment is not limited as long as a practical polishing rate is obtained. The pH is preferably 1.0 or more from the viewpoint of securing the polishing rate of the conductive substance part and / or the barrier layer. Similarly, the pH is preferably 12.0 or less, more preferably 6.0 or less, from the viewpoint of securing the polishing rate of the conductive material part and / or the barrier layer.

  In the case of using abrasive grains, the pH is preferably 1.5 or more, and more preferably 2.0 or more, from the viewpoint of the zeta potential, stability, etc. of the abrasive grains. Moreover, 4.0 or less is preferable from the same viewpoint, and 3.5 or less is more preferable.

  The pH of the polishing slurry for CMP can be measured with a pH meter (for example, “Model pH81” manufactured by Yokogawa Electric Corporation, “Model F-51” manufactured by Horiba, Ltd.).

[Preservation method]
The CMP polishing liquid of this embodiment may be stored as a one-part CMP polishing liquid containing all the components used, but the above components may be prepared and stored in a plurality of liquids. Good. A plurality of liquids are mixed so that each has a predetermined concentration immediately before polishing, and used as a polishing liquid for CMP. Depending on the component, if mixed in advance, the stability may decrease or the abrasive grains may aggregate. Storage in a plurality of liquids is preferable from the viewpoint of solving these problems. For example, (C) an aqueous solution of an oxidizing agent and a solution (or dispersion) containing other components may be divided into two liquids. (C) When hydrogen peroxide is used as an oxidizing agent, In this aspect, it is preferable to store and / or transport the aqueous solution of hydrogen peroxide and the solution (or dispersion) containing other components as two liquids and mix them before polishing.

  In addition, a single polishing liquid for CMP and a plurality of liquids in the case of two liquids are concentrated in terms of facilitating storage, transportation, etc., or in that the amount of each component can be adjusted according to the application. May be. Although there is no restriction | limiting in particular as a concentration ratio, About 2 to 10 times is preferable from the viewpoint of aiming at coexistence of the advantage of concentration and the density | concentration of the grade which a component does not precipitate. Concentration means that it is used after being diluted. In order to concentrate, in addition to evaporating a predetermined amount of water from the CMP polishing liquid, there is a method of reducing the amount of water in advance.

[Polishing method]
A polishing method according to an embodiment of the present invention includes a step of polishing an object to be polished using the CMP polishing liquid of the above embodiment. Examples of the polishing object include a semiconductor substrate, a magnetic head substrate, and a magnetic disk substrate.

  The polishing method of this embodiment is preferably applicable to the formation of metal wiring (wiring layer) in a semiconductor device. For example, a semiconductor substrate having a conductive material portion, a barrier layer, and an interlayer insulating film is polished by the polishing method of this embodiment. In the polishing under the same conditions, the polishing rate ratio of the conductive material part / barrier layer / interlayer insulating film is preferably 0.1 / 2/1 / 0.1-2.

  The polishing method of the present embodiment includes an interlayer insulating film having a raised portion (convex portion) and a groove portion (concave portion) on the surface (surface to be polished), a barrier layer that covers the interlayer insulating film along the surface, and the barrier A first polishing step of polishing the conductive material portion of the substrate having a conductive material portion covering the layer to expose a barrier layer located on the raised portion of the interlayer insulating film; And a second polishing step for exposing the raised portion of the interlayer insulating film by polishing the barrier layer exposed by the polishing step using the CMP polishing liquid of the above embodiment. The conductive material portion may cover the barrier layer so as to fill the groove portion of the interlayer insulating film.

  The CMP polishing liquid of the above embodiment is preferably used in the second polishing step for polishing the barrier layer, and the generation of organic residues on the metal wiring after the second polishing step can be reduced. When the generation of the organic residue is reduced, the accuracy of the pattern layout of the upper layer portion is improved and the occurrence of a short circuit between the metal wirings can be prevented.

  Examples of the interlayer insulating film include at least one selected from a silicon-based film and an organic polymer film. Silicon-based coatings: organosilicate glasses obtained using silicon dioxide, fluorosilicate glass, trimethylsilane, dimethoxydimethylsilane and the like as starting materials; silica-based coatings such as silicon oxynitride and silsesquioxane hydride; silicon carbide films And a silicon nitride film. Examples of the organic polymer film include wholly aromatic low dielectric constant films. Among these, a silicon dioxide film is particularly preferable. The interlayer insulating film can be formed by CVD, spin coating, dip coating, spraying, or the like. Specific examples of the interlayer insulating film include an interlayer insulating film in an LSI manufacturing process, particularly a multilayer wiring forming process.

  Examples of the constituent material of the conductive substance part include copper, copper alloy, copper oxide, copper alloy oxide, tungsten, tungsten alloy, a substance mainly composed of metal such as silver, gold, etc. Substances containing copper as the main component, such as copper, copper alloys, copper oxides, and copper alloy oxides, are preferred. As the conductive material portion, a film in which the material is formed by a known sputtering method, plating method or the like can be used.

  The barrier layer is formed in order to prevent the conductive material from diffusing into the interlayer insulating film and to improve the adhesion between the interlayer insulating film and the conductive material portion. The barrier layer is made of tantalum; tantalum compounds such as tantalum nitride and tantalum alloys; titanium; titanium compounds such as titanium nitride and titanium alloys; tungsten; tungsten compounds such as tungsten nitride and tungsten alloys; ruthenium; ruthenium such as ruthenium nitride and ruthenium alloys. Compound; Cobalt; Cobalt compound such as cobalt nitride and cobalt alloy is preferably included, and tantalum or a tantalum compound is more preferable. The barrier layer may have a single layer structure made of one of these or a laminated structure made of two or more layers.

  As a polishing apparatus, for example, when polishing with a polishing pad, the polishing apparatus includes a holder that can hold a substrate to be polished, and a polishing platen that is connected to a motor that can change the number of rotations and to which a polishing pad can be attached. A general polishing apparatus can be used. There is no restriction | limiting in particular as a polishing pad, A general nonwoven fabric, a foaming polyurethane, a porous fluororesin, etc. can be used.

  The polishing conditions are not limited, but the rotation speed of the surface plate is preferably a low rotation of 200 times / minute or less so that the substrate does not jump out. The pressure for pressing the surface to be polished of the substrate against the polishing pad is preferably 1 to 100 kPa, and 2 to 50 kPa is more preferable in order to satisfy the uniformity within the surface to be polished and the flatness of the pattern. During polishing, preferably, the polishing slurry for CMP of the above embodiment is continuously supplied to the polishing pad by a pump or the like. Although there is no restriction | limiting in this supply amount, For example, the quantity which can always coat | cover the surface of a polishing pad with polishing liquid is preferable.

  The substrate after polishing is preferably washed in running water and then dried after removing water droplets adhering to the substrate using spin drying or the like. Further, as a cleaning method, a known cleaning method can be applied in which a commercially available cleaning liquid is allowed to flow on the surface of the substrate to be polished and a brush made of polyurethane is rotated to remove deposits on the substrate by pressing with a constant pressure. .

  In order to perform CMP with the surface state of the polishing pad always the same, it is preferable to add a polishing pad conditioning step before polishing. For example, using a dresser with diamond particles, the polishing pad is conditioned with a liquid containing at least water. Subsequently, the polishing method of this embodiment is performed.

  Hereinafter, the polishing method of this embodiment will be further described by taking the formation of a wiring layer in a semiconductor device as an example.

  First, an interlayer insulating film made of silicon dioxide or the like is laminated on a silicon substrate. Next, a groove portion having a predetermined pattern is formed on the surface of the interlayer insulating film by a known means such as resist layer formation or etching to obtain an interlayer insulating film having a raised portion and a groove portion. A barrier layer made of tantalum or the like is formed on the interlayer insulating film by vapor deposition or CVD, and a barrier layer that covers the interlayer insulating film along the surface irregularities is obtained. Further, a conductive material portion made of copper or the like that fills the concave portion and covers the barrier layer is formed by vapor deposition, plating, CVD, or the like. The thickness of each layer is appropriately determined according to the type of the semiconductor device. For example, the thickness of the interlayer insulating film is preferably about 0.01 to 2.0 μm, and the thickness of the barrier layer is 0.01. The thickness of the conductive material portion is preferably about 0.01 to 3.0 μm.

  Next, for example, the conductive material portion on the surface of the substrate is polished by CMP using a polishing slurry for the conductive material having a sufficiently large polishing rate ratio of the conductive material portion / barrier layer (first polishing). Process). As a result, a desired wiring pattern in which the barrier layer located on the raised portion of the interlayer insulating film is exposed on the surface and the conductive material remains in the groove portion is obtained. As this polishing proceeds, a part of the barrier layer located on the raised portion of the interlayer insulating film may be polished simultaneously with the conductive material portion. The wiring pattern surface obtained by the first polishing process is polished using the CMP polishing liquid of the above embodiment as a surface to be polished in the second polishing process.

  In the second polishing step, while the polishing surface of the obtained substrate is pressed against the polishing pad, the polishing surface plate and the substrate are supplied while supplying the CMP polishing liquid of the above embodiment between the polishing pad and the polishing surface. The barrier layer exposed by the first polishing step is polished by relatively moving. The CMP polishing liquid of the above embodiment can polish the conductive material portion, the barrier layer, and the interlayer insulating film, but in the second polishing step, at least the exposed barrier layer is polished.

  Desired pattern in which all the raised portions of the interlayer insulating film covered with the barrier layer are exposed, the conductive material portion that becomes the wiring layer is left in the groove portion, and the cross section of the barrier layer is exposed at the boundary between the raised portion and the groove portion Polishing is finished when

  In order to ensure excellent flatness at the end of polishing, an amount including a part of the raised portion of the interlayer insulating film may be further polished by overpolishing. For example, when the time until a desired pattern is obtained in the second polishing step is 100 seconds, polishing may be performed by adding 50 seconds in addition to the polishing for 100 seconds.

  A passivation layer, an interlayer insulating film, a barrier layer, and a second conductive material portion are further formed on the wiring layer formed in this way, and polished to obtain a smooth surface over the entire surface of the semiconductor substrate. And By repeating this step a predetermined number, a semiconductor device having a desired number of wiring layers can be manufactured.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples without departing from the technical idea of the present invention. For example, the kind of polishing liquid material and the blending ratio thereof may be other than the kind and blending ratio described in the present embodiment.

[Example 1]
BTA 0.10 parts by mass, citric acid 0.4 parts by mass, 30% by mass hydrogen peroxide solution 1.0 part by mass, tartaric acid 0.1 parts by mass, polyacrylic acid (weight average molecular weight 8,000) 0.1 parts by mass Then, 1.0 part by mass of methanol and 97.3 parts by mass of water were stirred and mixed to prepare a polishing slurry for CMP (1). The CMP polishing liquid (1) had a pH of 2.3.
In order to facilitate the confirmation of the presence or absence of “precipitates” described later, no abrasive grains were blended in the CMP polishing liquid (1). The same applies to the following polishing liquids for CMP (2) to (8).

<Measurement method of pH>
A pH meter (manufactured by Horiba, Ltd., “Model F-51”) was used for pH measurement. Standard buffer (phthalate pH buffer pH: 4.21 (25 ° C.), neutral phosphate pH buffer pH 6.86 (25 ° C.), borate pH buffer pH: 9.04 (25 ° C. )), The electrode was put in a CMP polishing liquid (25 ° C.), and the value after 3 minutes had passed and stabilized was measured.

[Examples 2 to 4]
The components shown in Table 1 were mixed and operated in the same manner as in Example 1 to prepare CMP polishing liquids (2) to (4).

[Comparative Example 1]
0.10 parts by mass of BTA, 1.0 part by mass of 30% aqueous hydrogen peroxide, 0.1 part by mass of tartaric acid, 0.1 part by mass of polyacrylic acid (weight average molecular weight 8,000), 1.0 part by mass of methanol and water 97.7 parts by mass of the mixture was stirred and mixed to prepare a polishing slurry for CMP (5). The pH of the polishing slurry for CMP (5) was 2.8.

[Comparative Examples 2 to 4]
The components shown in Table 1 were mixed and operated in the same manner as in Comparative Example 1 to prepare CMP polishing liquids (6) to (8).

<Evaluation of precipitate>
After adding 0.2 parts by mass of copper hydroxide (II) to 100 parts by mass of CMP polishing liquids (1) to (8), stirring, and allowing to stand for one day, The presence or absence was confirmed visually. When the complex is dissolved in water, no precipitate is observed. Conversely, when the complex is not dissolved in water, a precipitate (solid) appears in the CMP polishing liquid. The results are shown in Table 1.

  The “after standing for one day” means after 24 to 25 hours after adding the copper hydroxide (II).

  As shown in Table 1, insoluble copper complexes did not precipitate in CMP polishing liquids (1) to (4) containing citric acid of 3.0 times or more relative to BTA. In contrast, in the CMP polishing liquids (5) to (7) containing no citric acid, insoluble copper complexes were precipitated. Further, insoluble copper complex was also deposited in the polishing slurry for CMP (8) containing citric acid but having a content of less than 3.0 times that of BTA.

  That is, in the polishing slurry for CMP containing citric acid of 3.0 times or more with respect to BTA, insoluble copper complexes were not formed, and precipitates could be reduced.

  The effects of the embodiment of the present invention have been shown using the above examples. In addition to (A) benzotriazole and (B) benzotriazole used in the examples, 3.0 times or more of citric acid, and (C) an oxidizing agent, an abrasive such as an optional component, a metal dissolving agent, etc. Similarly, excellent effects can be obtained when used.

  It has been known that a complex of a conductive substance and BTA is insoluble in water, and many organic residues are generated. According to the polishing slurry for CMP that is an embodiment of the present invention, a complex of a conductive substance, BTA, and citric acid is formed and becomes water-soluble, so that the detergency is improved and the organic residue is reduced.

[Examples 5 to 8]
Polishing liquids for CMP (9) to (12) in which 5.0 parts by mass of colloidal silica particles were added to the polishing liquids for CMP (1) to (4) in Examples 1 to 4 and the same part by mass of water was reduced. Was created respectively. Using the obtained polishing liquids for CMP (9) to (12), the barrier layer was polished in the step of forming the embedded wiring on the semiconductor substrate (used in the second polishing step). It was confirmed that a part of the barrier layer and the interlayer insulating film layer was removed well, and organic residue was not observed on the surface to be polished by visual observation, and it became a CMP polishing liquid suitable for the second polishing step. It was.

DESCRIPTION OF SYMBOLS 1 Interlayer insulating film 2 Barrier conductor layer 3 Conductive substance part 100 Substrate before polishing 200 Substrate after polishing

Claims (15)

  A polishing slurry for CMP, comprising (A) benzotriazole, (B) citric acid at least 3.0 times the amount of benzotriazole, and (C) an oxidizing agent.   The polishing liquid for CMP according to claim 1, wherein the content of the (A) benzotriazole is 0.01 to 2 parts by mass with respect to 100 parts by mass of the polishing liquid for CMP.   The CMP polishing liquid according to claim 1 or 2, wherein the content of the (B) citric acid is 8.0 parts by mass or less with respect to 100 parts by mass of the CMP polishing liquid.   The (C) oxidizing agent includes at least one selected from the group consisting of hydrogen peroxide, periodate, persulfate, hypochlorite, and ozone. Polishing liquid for CMP as described in 2. above.   (D) Polishing liquid for CMP as described in any one of Claims 1-4 which further contains an abrasive grain.   The CMP (D) according to claim 5, wherein the abrasive grains (D) include at least one selected from the group consisting of silica particles, alumina particles, ceria particles, titania particles, zirconia particles, germania particles, and modified products thereof. Polishing fluid.   (E) CMP polishing liquid as described in any one of Claims 1-6 which further contains a metal dissolving agent.   The CMP agent according to claim 7, wherein the (E) metal solubilizer includes at least one selected from the group consisting of organic acids, organic acid esters, ammonium salts of organic acids, inorganic acids, and ammonium salts of inorganic acids. Polishing fluid.   (F) Polishing liquid for CMP as described in any one of Claims 1-8 which further contains a water-soluble polymer.   (G) Polishing liquid for CMP as described in any one of Claims 1-9 which further contains an organic solvent.   (G) The organic solvent is at least one selected from the group consisting of carbonate esters, lactones, glycols, alcohols, ethers, ketones, esters, amides, sulfolanes, and glycol derivatives. The polishing slurry for CMP according to claim 10, further comprising:   The grinding | polishing method which grind | polishes a grinding | polishing target object using the polishing liquid for CMP as described in any one of Claims 1-11. The conductive material of a substrate having an interlayer insulating film having a raised portion and a groove on the surface, a barrier conductor layer covering the interlayer insulating film along the surface, and a conductive material portion covering the barrier conductor layer A first polishing step of polishing a portion to expose a barrier conductor layer located on the raised portion of the interlayer insulating film;
The said 2nd grinding | polishing which polishes the said barrier conductor layer exposed by the 1st grinding | polishing process using the polishing liquid for CMP as described in any one of Claims 1-11, and exposes the protruding part of the said interlayer insulation film. A polishing method comprising: a step.   The polishing method according to claim 13, wherein the conductive substance part contains at least one selected from the group consisting of copper, a copper alloy, a copper oxide, and a copper alloy oxide.   The barrier conductor layer contains at least one selected from the group consisting of tantalum, a tantalum compound, titanium, a titanium compound, tungsten, a tungsten compound, ruthenium, a ruthenium compound, cobalt, and a cobalt compound. Polishing method.

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