JP2015137350A - Polishing liquid and polishing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid capable of improving surface flatness of a film to be polished in a chemical mechanical polishing (CMP) technology for polishing the film to be polished formed on a surface of a substrate and a polishing method using the same.SOLUTION: There is provided a polishing liquid containing particles containing cerium oxide, a flattening agent, an organic acid compound, a pH adjustment agent, and water, where the flattening agent is an acrylic acid-based polymer, the organic acid compound is an organic compound having a sulfo group and an amino group, and pH is 4.0 to 6.0. The blended amount of the flattening agent is 0.01 to 1 mass% based on the total mass of the polishing liquid, the flattening agent is a single polymer of acrylic acid or methacrylic acid, or at least one kind selected from a copolymer of acrylic acid and methacrylic acid and a copolymer of acrylic acid or methacrylic acid and other copolymerizable monomer, and the organic acid compound is at least one kind selected from 4-aminobenzene sulfonic acid (sulfanilic acid) and amidosulfuric acid (sulfamic acid) of 0.001 to 1 mass% based on the total mass of the polishing liquid.

Description

  The present invention relates to a polishing liquid and a polishing method using the polishing liquid. More specifically, the present invention relates to a polishing liquid for polishing a substance used as an insulating material and a polishing method using the polishing liquid.

  In the current ULSI semiconductor device manufacturing process, processing techniques for increasing the density and miniaturization of semiconductor devices are being researched and developed. CMP (Chemical Mechanical Polishing) technology, which is one of the processing technologies, includes planarization of interlayer insulating material, shallow trench isolation (STI) formation, plug and embedded metal wiring formation, etc. in the semiconductor device manufacturing process. In doing so, it has become an indispensable technique.

  Conventionally, in a semiconductor device manufacturing process, an inorganic insulating film such as a silicon oxide film is formed by a method such as plasma CVD (chemical vapor deposition) or low pressure CVD (chemical vapor deposition). As a chemical mechanical polishing liquid for planarizing the inorganic insulating film, it has been generally studied to use a fumed silica-based polishing liquid. The fumed silica-based polishing liquid is produced by adjusting the pH of the polishing liquid containing particles obtained by grain growth by a method such as thermal decomposition of silicon tetrachloride. However, such a fumed silica-based polishing liquid has a technical problem that the polishing rate is low.

  On the other hand, a cerium oxide polishing liquid containing cerium oxide particles is used as a polishing liquid for glass surfaces such as photomasks and lenses. Cerium oxide particles have a lower hardness than silica particles and alumina particles, and are difficult to scratch on the polished surface during polishing, and thus are useful for finish mirror polishing. Further, the cerium oxide polishing liquid has an advantage that the polishing rate is faster than the silica polishing liquid such as fumed silica type or colloidal silica type.

  As a cerium oxide polishing liquid, the following Patent Document 1 describes a semiconductor CMP polishing liquid using high-purity cerium oxide abrasive grains. Patent Document 2 below describes a technique of adding an additive to control the polishing rate of a cerium oxide polishing liquid and improve global flatness.

Japanese Patent Laid-Open No. 10-106994 Japanese Patent No. 3278532

  However, with the progress of miniaturization of design rules for wiring and STI, further improvement in flatness is required for the cerium oxide polishing liquid as described above.

  The present invention has been made in view of the above circumstances, and in a CMP technique for polishing a film to be polished formed on the surface of a substrate, a polishing liquid capable of improving the surface flatness of the film to be polished and the polishing liquid An object of the present invention is to provide a polishing method using a polishing liquid.

  The polishing liquid according to the present invention contains particles containing cerium oxide, a planarizing agent, an organic acid compound, a pH adjusting agent, and water, and the planarizing agent is an acrylic acid polymer, The organic acid compound is an organic compound having at least one selected from the group consisting of a sulfonic acid group and a sulfonic acid group as a functional group, and a polishing liquid having a pH of 4.0 or more and 6.0 or less.

  According to the polishing liquid of the present invention, in a CMP technique for polishing a film to be polished (for example, an interlayer insulating film, a BPSG film (boron, phosphorus-doped silicon dioxide film), an STI film) formed on the surface of a substrate. The surface flatness after polishing of the polishing film can be improved.

  The blending amount of the leveling agent is preferably 0.01 to 1% by mass with respect to the total mass of the polishing liquid.

  The leveling agent may be a homopolymer of acrylic acid or methacrylic acid, a copolymer of acrylic acid and methacrylic acid, and acrylic acid or methacrylic acid and other copolymerizable monomers. It may be at least one selected from the group consisting of copolymers.

  It is preferable that the compound which has a sulfo group and an amino group is 0.001-1 mass% with respect to the total mass of polishing liquid.

  The compound having a sulfo group and an amino group is preferably at least one selected from 4-aminobenzenesulfonic acid (sulfanilic acid) and amidosulfuric acid (sulfamic acid).

  In the polishing method according to the present invention, at least a part of the insulating material is removed by CMP using the polishing liquid.

  According to the present invention, in a CMP technique for polishing a film to be polished (for example, an STI film) formed on the surface of a substrate, the polishing liquid capable of improving the surface flatness after polishing of the film to be polished and this polishing A method for polishing a substrate using a liquid can be provided.

It is a schematic cross section which shows one Embodiment of the grinding | polishing method.

  Hereinafter, embodiments of the present invention will be described in detail.

<Polishing liquid>
The polishing liquid according to the present embodiment includes a step of mixing particles containing cerium oxide, a leveling agent, a compound having a sulfo group and an amino group, a pH adjusting agent, and water, A polymer obtained by polymerizing at least one selected from the group consisting of acrylic acid and methacrylic acid, wherein the compound having a sulfo group and an amino group is at least selected from the group consisting of a sulfonic acid group and a sulfonic acid group It is an organic compound having one type as a functional group, and is a polishing liquid having a pH of 4.0 or more and 6.0 or less.

(Cerium oxide particles)
There is no restriction | limiting in particular as a cerium oxide particle, A well-known thing can be used. In general, cerium oxide particles can be obtained by oxidizing cerium salts such as carbonates, nitrates, sulfates and oxalates. Examples of the method for producing the cerium oxide particles include a firing method by firing, an oxidation method using hydrogen peroxide, and the like.

  When cerium oxide particles are used for polishing a silicon oxide film formed by TEOS-CVD or the like, the larger the crystallite diameter (crystallite diameter) of the cerium oxide particles and the smaller the crystal distortion (that is, the crystal The higher the property, the faster the polishing is possible, but the material to be polished tends to have polishing scratches. From this point of view, the cerium oxide particles are preferably composed of two or more crystallites, particles having a crystal grain boundary, and more preferably particles having a crystallite diameter of 5 to 300 nm.

  The content of alkali metal and halogens in the cerium oxide particles is preferably 10 mass ppm or less because it is suitably used for polishing in the manufacture of semiconductor elements.

  The average particle diameter of the cerium oxide particles is preferably 10 to 500 nm, more preferably 20 to 400 nm, and still more preferably 50 to 300 nm. If the average particle size of the cerium oxide particles is 10 nm or more, a good polishing rate tends to be obtained, and if it is 500 nm or less, the material to be polished tends to be hardly damaged.

  Here, the average particle diameter of the cerium oxide particles is a laser diffraction particle size distribution meter (for example, manufactured by Horiba, Ltd., trade name: LA-920, refractive index: 1.93, light source: He—Ne laser, absorption 0). ) (D50 value (median diameter of volume distribution, cumulative median value)). For the measurement of the average particle diameter, a sample in which the polishing liquid is diluted to an appropriate concentration (for example, a concentration at which the measurement transmittance (H) with respect to the He—Ne laser is 60 to 70%) is used. In addition, when the polishing liquid containing cerium oxide particles is stored separately as a cerium oxide polishing liquid in which cerium oxide particles are dispersed in water and an additive liquid in which additives are dissolved in water, as will be described later. The cerium oxide polishing liquid can be measured by diluting to an appropriate concentration.

  The content of the cerium oxide particles is preferably 0.1 to 20% by mass, more preferably 0.1 to 15% by mass, and 0.5 to 10% by mass based on the total mass of the polishing liquid. More preferably. If the content of the cerium oxide particles is 0.1% by mass or more, a good polishing rate tends to be obtained. If the content is 20% by mass or less, the aggregation of particles is suppressed and the material to be polished is damaged. There is a tendency to become difficult.

(Flattening agent)
The leveling agent is an acrylic acid polymer. Here, the acrylic polymer is defined as a polymer having a structure obtained by polymerizing at least one selected from the group consisting of acrylic acid and methacrylic acid, and the production method thereof is not particularly limited.

  The leveling agent may be a homopolymer of acrylic acid or methacrylic acid, a copolymer of acrylic acid and methacrylic acid, and other copolymerizable monomers (acrylic acid or acrylic acid or methacrylic acid). It may be at least one selected from the group consisting of copolymers with acid and methacrylic acid. The “other copolymerizable monomer” in the copolymer may be any monomer that can be copolymerized with acrylic acid and / or methacrylic acid, and examples thereof include styrene, ethylene, and propylene.

  The leveling agent is preferably a homopolymer of acrylic acid. A flattening agent can be used individually by 1 type or in combination of 2 or more types.

  The content of the leveling agent in the polishing liquid is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, and still more preferably 0.05% or more with respect to the total mass of the polishing liquid. The content of the leveling agent is preferably 1% by mass or less, more preferably 0.75% by mass or less, and still more preferably 0.5% by mass or less with respect to the total mass of the polishing liquid. When the content of the planarizing agent is 0.01% by mass or more and 1% by mass or less, the polishing rate of the film to be polished can be improved and the surface flatness after polishing can be improved.

  Although there is no restriction | limiting in particular in the weight average molecular weight of a planarizing agent, It is preferable that it is 100-150,000, and it is more preferable that it is 1000-80000. If the weight average molecular weight of the dispersant is 100 or more, a good polishing rate tends to be easily obtained when a material to be polished such as a silicon oxide film or a silicon nitride film is polished. If the weight average molecular weight of the dispersant is 150,000 or less, the storage stability of the polishing liquid tends to be difficult to decrease. The weight average molecular weight is a value measured by GPC (gel permeation chromatography) and converted to standard polyoxyethylene.

(Compound having sulfo group and amino group)
The polishing liquid according to this embodiment contains a compound having a sulfo group (—SO ₃ H) and an amino group (—NH ₂ , —NHR or —NRR ′). Thereby, it becomes easy to improve the flatness of the material to be polished (for example, a silicon oxide film) after the polishing of the film to be polished. More specifically, in addition to shortening the polishing time when polishing a surface to be polished having irregularities, it becomes easy to suppress the phenomenon that a part is excessively polished and recessed like a dish, so-called dishing. . The compound having a sulfonic acid group and an amino group may form a salt. The compound which has a sulfonic acid group and an amino group can be used individually by 1 type or in combination of 2 or more types.

Examples of the compound having a sulfo group and an amino group include 3-aminobenzenesulfonic acid, 4-aminobenzenesulfonic acid (sulfanilic acid), aminomethanesulfonic acid, 1-aminoethanesulfonic acid, 2-amino-1-ethane. Examples thereof include aminosulfonic acids such as sulfonic acid (taurine) and 1-aminopropane-2-sulfonic acid, sulfamic acids such as amidosulfuric acid (sulfamic acid), N-methylsulfamic acid, phenylsulfamic acid, and N-cyclohexylsulfamic acid. Among them, those having a primary amino group (—NH ₂ ) are preferable, benzenesulfonic acids such as 3-aminobenzenesulfonic acid and 4-aminobenzenesulfonic acid, and amidosulfuric acid are more preferable, and 4-aminobenzenesulfonic acid and Amidosulfuric acid is particularly preferred.

  The content of the compound having a sulfo group and an amino group is preferably 0.001 to 1% by mass, and more preferably 0.01 to 0.5% by mass with respect to the total mass of the polishing liquid. If the content is 0.001% by mass or more, the flatness of the material to be polished (eg, silicon oxide film) after polishing tends to be improved. There is a tendency to sufficiently improve the polishing rate.

(PH adjuster)
The polishing liquid according to this embodiment can be adjusted to a desired pH by adding a pH adjuster as necessary. The pH adjuster is not particularly limited, and examples thereof include acid components such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, and acetic acid; base components such as sodium hydroxide, ammonia, potassium hydroxide, and calcium hydroxide. Is mentioned. When the polishing liquid is used for semiconductor polishing, ammonia and an acid component are preferably used. As the pH adjuster, an ammonium salt of a water-soluble polymer that has been partially neutralized with ammonia in advance can also be used.

(water)
Although it does not restrict | limit especially as water, Deionized water, ion-exchange water, ultrapure water, etc. are preferable. The water content is not particularly limited as long as it is the remainder of the content of each of the above-described components and is contained in the polishing liquid. The polishing liquid may further contain a solvent other than water, for example, a polar solvent such as ethanol or acetone, as necessary.

(PH)
The pH (25 ° C.) of the polishing liquid is preferably 4.0 to 6.0, and more preferably 4.5 to 5.5. When the pH is 4.0 or more and 6.0 or less, the polishing rate of the film to be polished can be improved and the surface flatness after polishing can be improved.

  The pH of the polishing liquid can be measured using a pH meter (for example, Model PH81 (trade name) manufactured by Yokogawa Electric Corporation). For example, after calibrating two points using a standard buffer solution (phthalate pH buffer solution pH: 4.21 (25 ° C.), neutral phosphate pH buffer solution pH: 6.86 (25 ° C.)), the electrode Is put into a polishing liquid, and the value after being stabilized at 25 ° C. for 2 minutes or more is measured.

(Other additives)
The polishing liquid according to this embodiment may contain a compound other than the planarizing agent, the compound having a sulfo group and an amino group, and a pH adjuster as an additive. Examples of such additives include water-soluble polymer compounds, water-soluble cationic compounds, water-soluble anionic compounds, water-soluble nonionic compounds, and water-soluble amphoteric compounds.

  Examples of water-soluble polymer compounds include polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan and pullulan; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polyamic acid, ammonium polyamic acid, sodium polyamic acid Examples thereof include salts and polycarboxylic acids such as polyglyoxylic acid and salts thereof; vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and polyacrolein.

  Examples of the water-soluble cationic compound include polyvinyl pyrrolidone, coconut amine acetate, stearyl amine acetate and the like.

  Examples of the water-soluble anionic compound include lauryl sulfate triethanolamine, ammonium lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and a special polycarboxylic acid type polymer compound.

  Examples of water-soluble nonionic compounds include polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2-hydroxyethyl Methacrylate, alkyl alkanolamide and the like can be mentioned.

  Examples of the water-soluble amphoteric compound include lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine and the like.

  These additives can be used alone or in combination of two or more.

  The content of the other additives is preferably 0.01 to 5% by mass based on the total mass of the polishing liquid.

  The constituents of the polishing liquid may be stored in two or more liquids so as to be the polishing liquid. For example, the cerium oxide polishing liquid containing cerium oxide particles and water and the additive liquid containing an additive and water may be stored separately.

<Manufacturing method of polishing liquid>
The manufacturing method of the polishing liquid according to the present embodiment includes, for example, a cerium oxide production process and a dispersion process. In the cerium oxide production step, cerium oxide particles are produced by a firing method, an oxidation method, or the like. For example, cerium salt is fired to obtain cerium oxide particles (firing step). In the dispersion step, cerium oxide particles, a dispersant, and water are mixed to disperse the cerium oxide particles in water. The blending amount of the dispersant is adjusted so as to obtain a polishing liquid having the above-described dispersant content, and is preferably 0.001 to 4% by mass with respect to the total mass of the cerium oxide particles.

<Polishing method>
In the polishing method according to this embodiment, at least a part of the insulating material is removed by CMP using the polishing liquid. In the polishing method according to the present embodiment, for example, a substrate having an insulating material on the surface is polished (substrate polishing method). The polishing method according to the present embodiment includes, for example, a preparation process, a substrate arrangement process, and a polishing process. In the preparation step, a substrate having an insulating material on the surface is prepared. In the substrate placement step, the substrate is placed so that the insulating material faces the polishing cloth. In the polishing step, for example, at least a part of the insulating material is removed. In the polishing step, for example, a polishing liquid is supplied between the polishing cloth and the insulating material in a state where the insulating material of the substrate on which the insulating material is formed is pressed against the polishing cloth of the polishing surface plate, so that the substrate and the polishing plate are fixed. At least a part of the insulating material is polished by moving the board relatively. The shape of the insulating material is not particularly limited, and is, for example, a film shape (insulating film).

  As a substrate, an insulating material (for example, an inorganic insulating material) on a semiconductor substrate such as a substrate related to semiconductor element manufacture, for example, a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed, or a semiconductor substrate at a stage where a circuit element is formed A substrate on which is formed. Examples of the insulating material include inorganic insulating materials such as a silicon oxide film, a silicon nitride film, and a composite film of a silicon oxide film. By polishing the insulating material formed on such a semiconductor substrate with the polishing liquid according to the present embodiment, unevenness on the surface of the insulating material can be eliminated, and a smooth surface can be obtained over the entire surface of the semiconductor substrate. Further, the polishing liquid according to the present embodiment can also be used for shallow trench isolation.

  Hereinafter, the polishing method will be described in more detail by taking the case of a semiconductor substrate on which an insulating material is formed as an example. FIG. 1 is a schematic cross-sectional view showing an example of a polishing method. First, as shown in FIG. 1 (A), a substrate 100 having a wafer 1 having concave and convex portions formed on its surface and a silicon nitride film 2 formed on the convex portion of the wafer 1. Prepare. Next, as shown in FIG. 1B, a silicon oxide film 3 is deposited by plasma TEOS or the like so as to fill the irregularities on the surface of the wafer 1 to obtain a substrate 200.

  Then, using the polishing liquid, the silicon oxide film 3 is polished and removed until the silicon nitride film 2 on the convex portion of the wafer 1 is exposed. In the substrate after polishing, as shown in FIG. 1C, it is preferable that the dishing amount 6 that is a value obtained by subtracting the thickness 5 of the silicon oxide film 3 in the trench portion from the depth 4 of the trench portion is small. .

  The polishing apparatus generally includes a holder for holding a semiconductor substrate having a material to be polished and a polishing surface plate to which a motor capable of changing the number of rotations is attached and to which a polishing cloth (pad) can be attached. A typical polishing apparatus can be used. As a polishing apparatus, for example, a polishing apparatus manufactured by Ebara Manufacturing Co., Ltd., model number: EPO-111, manufactured by Applied Materials, trade name: MIRRA, Reflexion (“MIRRA”, “Reflexion” are registered trademarks), etc. can be used. .

  As the polishing cloth, a general nonwoven fabric, foamed polyurethane, porous fluororesin and the like can be used without particular limitation. Moreover, it is preferable that the polishing cloth is subjected to groove processing so that the polishing liquid is accumulated.

The polishing conditions are not limited, but the rotation speed of the surface plate is preferably a low rotation of 200 min ⁻¹ or less so that the semiconductor substrate does not pop out, and the pressure (working load) applied to the semiconductor substrate is scratched after polishing. 100 kPa or less is preferable so that it does not occur. During polishing, the polishing liquid is continuously supplied to the polishing cloth with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of polishing cloth is always covered with polishing liquid.

  The semiconductor substrate after polishing is preferably washed in running water and then dried by removing water droplets adhering to the semiconductor substrate using a spin dryer or the like.

  By polishing the insulating material, which is the material to be polished, with the polishing liquid in this manner, surface irregularities can be eliminated and a smooth surface can be obtained over the entire surface of the semiconductor substrate. After the flattened shallow trench is formed, aluminum wiring is formed on the insulating material, the insulating material is formed again between the wirings and on the wiring, and then the insulating material is polished using the polishing liquid. Get a smooth surface. By repeating this step a predetermined number of times, a semiconductor substrate having a desired number of layers can be manufactured.

  Examples of the insulating material polished by the polishing liquid according to the present embodiment include inorganic insulating materials such as a silicon oxide film and a silicon nitride film. The silicon oxide film may be doped with an element such as phosphorus or boron. As a method for manufacturing the inorganic insulating material, a low pressure CVD method, a plasma CVD method, or the like can be given.

The silicon oxide film formation by the low pressure CVD method uses monosilane: SiH ₄ as the Si source and oxygen: O ₂ as the oxygen source. A silicon oxide film can be obtained by performing this SiH ₄ —O ₂ -based oxidation reaction at a low temperature of 400 ° C. or lower. In some cases, the silicon oxide film obtained by CVD is heat-treated at a temperature of 1000 ° C. or lower. In order to planarize the surface by high-temperature reflow, when doping silicon: P with phosphorus: P, it is preferable to use a SiH ₄ —O ₂ —PH ₃ -based reactive gas.

The plasma CVD method has an advantage that a chemical reaction requiring a high temperature can be performed at a low temperature under normal thermal equilibrium. There are two plasma generation methods, capacitive coupling type and inductive coupling type. The reaction gases, SiH ₄ as an Si source, an oxygen source as _{N 2} O was used was _SiH 4 -N ₂ O-based gas and TEOS-O-based gas using tetraethoxysilane (TEOS) in an Si source (TEOS-plasma CVD method). The substrate temperature is preferably 250 to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa.

Silicon nitride film formation by the low pressure CVD method uses dichlorosilane: SiH ₂ Cl ₂ as a Si source and ammonia: NH ₃ as a nitrogen source. A silicon nitride film is obtained by performing this SiH ₂ Cl ₂ —NH ₃ -based oxidation reaction at a high temperature of 900 ° C. Examples of the reaction gas used for forming the silicon nitride film by the plasma CVD method include SiH ₄ —NH ₃ gas using SiH ₄ as the Si source and NH ₃ as the nitrogen source. The substrate temperature is preferably 300 to 400 ° C.

  The polishing liquid and the polishing method according to the present embodiment can be applied not only to the insulating material formed on the semiconductor substrate but also to various semiconductor device manufacturing processes. The polishing liquid and the polishing method according to this embodiment include, for example, an inorganic insulating material such as a silicon oxide film, glass, and a silicon nitride film formed on a wiring board having a predetermined wiring, polysilicon, Al, Cu, Ti, and TiN. , W, Ta, TaN films, optical glasses such as photomasks, lenses, and prisms, inorganic conductive films such as ITO, optical integrated circuits composed of glass and crystalline materials, optical switching elements, optical waveguides Polishing optical fiber end faces, scintillator and other optical single crystals, solid state laser single crystals, blue laser LED sapphire substrates, semiconductor single crystals such as SiC, GaP, and GaAs, glass substrates for magnetic disks, magnetic heads, etc. Can also be applied.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to these Examples.

(Production of cerium oxide powder)
40 kg of commercially available cerium carbonate hydrate was placed in an alumina container and baked in air at 830 ° C. for 2 hours to obtain 20 kg of yellowish white powder. When the phase of this powder was identified by the X-ray diffraction method, it was confirmed to be cerium oxide. 20 kg of the obtained cerium oxide powder was dry-ground using a jet mill to obtain a cerium oxide powder containing cerium oxide particles.

Example 1
Mixing 200.0 g of the cerium oxide prepared above and 795.0 g of deionized water, adding 5 g of an aqueous solution of ammonium polyacrylate (weight average molecular weight: 8000, 40 mass%), and ultrasonically dispersing while stirring To obtain a cerium oxide dispersion. Ultrasonic dispersion was performed at an ultrasonic frequency of 400 kHz and a dispersion time of 20 minutes.

  Thereafter, 1 kg of a cerium oxide dispersion was placed in a 1 liter container (height: 170 mm) and allowed to stand to perform sedimentation classification. After 15 hours of classification time, the supernatant above a depth of 13 cm from the water surface was pumped up. The obtained supernatant cerium oxide dispersion was then diluted with deionized water to obtain a cerium oxide slurry so that the solid content concentration was 5% by mass.

  In order to measure the average particle diameter (D50) of cerium oxide in the cerium oxide slurry, the slurry was diluted so that the measurement transmittance (H) with respect to the He—Ne laser was 60 to 70%, did. When this measurement sample was measured with a laser diffraction particle size distribution analyzer (for example, manufactured by HORIBA, Ltd., trade name: LA-920, refractive index: 1.93, light source: He—Ne laser, absorption 0), the value of D50 was measured. Was 100 nm.

  As a compound having a sulfo group and an amino group, 18.2 g of 4-aminobenzenesulfonic acid and 700 g of deionized water are mixed, and a terminal group having a weight average molecular weight of 4000 and 40% by mass is used as a leveling agent. 8.75 g of an aqueous polyacrylic acid solution was added, and aqueous ammonia (25% by mass) was added to adjust the pH to 4.5. Further, deionized water was added to make the total amount of 750 g as an additive solution.

  Here, 200 g of the cerium oxide slurry is added, ammonia water (25% by mass) is added to adjust to pH 5.0, deionized water is further added to make the total amount 1000 g, and a cerium oxide polishing liquid ( (Cerium oxide solid content: 1.0% by mass).

  Further, a measurement sample was prepared in the same manner as described above, and the average particle size of the particles in the polishing liquid was measured with a laser diffraction particle size distribution meter. As a result, the value of D50 was 100 nm.

(Insulating film polishing)
As the polishing test wafer, a trade name: pattern wafer 864 (diameter: 200 mm) manufactured by SEMATECH was used. The polishing test wafer and a method for evaluating polishing characteristics using the wafer will be described with reference to FIG.

  FIG. 1A is an enlarged schematic cross-sectional view of a part of the wafer 1. A plurality of grooves are formed on the surface of the wafer 1, and a silicon nitride film 2 having a thickness of 150 nm is formed on the convex surface of the wafer 1. The depth of the groove (step difference from the surface of the convex portion to the bottom surface of the concave portion) is 500 nm. Hereinafter, the convex portion is referred to as an active portion, and the concave portion is referred to as a trench portion. The wafer 1 is formed with trench / active portions of 100 μm / 100 μm, 20 μm / 80 μm, and 80 μm / 20 μm.

  FIG. 1B is an enlarged schematic cross-sectional view of a part of a polishing test wafer. In the polishing test wafer, the silicon oxide film 3 is formed in the active region and the trench portion by the plasma TEOS method so that the thickness of the silicon oxide film 3 from the surface of the active region becomes 600 nm. In the polishing test, the silicon oxide film 3 of the polishing test wafer is polished and planarized.

  FIG. 1C is a schematic cross-sectional view in which a part of a polishing test wafer after polishing the silicon oxide film 3 is enlarged. Polishing is completed on the surface of the silicon nitride film 2 in the active region, and the time required for polishing at this time is defined as polishing time, and a value obtained by subtracting the thickness 5 of the silicon oxide film 3 in the trench from the depth 4 of the trench. The dishing amount is 6. The dishing amount 6 should be small.

  A polishing apparatus (manufactured by Applied Materials, trade name: MIRRA) was used for polishing the polishing test wafer. A polishing test wafer was set in a holder on which a suction pad for mounting the substrate was attached. A polishing cloth made of porous urethane resin (groove shape = perforate type: manufactured by Rohm and Haas, model number: IC1010) was attached to the polishing surface plate of the polishing apparatus. Further, the holder was placed on the polishing surface plate with the insulating film (silicon oxide film) surface as the film to be polished facing down, and the processing load was set to 5 psi (34.5 kPa).

While the cerium oxide polishing liquid was dropped on the polishing platen at a rate of 150 ml / min, the polishing platen and the polishing test wafer were each operated at a rotational speed of 125 min ⁻¹ to polish the polishing test wafer. The polished test wafer after polishing was thoroughly washed with pure water and then dried.

  For the polished test wafer after polishing, the remaining film thickness of the trench part / active part: 100 μm / 100 μm is determined by using the interference type film thickness measuring device NanoSpec / AFT5100 manufactured by Nanometrics (trade name (“NanoSpec” is a registered trademark). ))) And the dishing amount was evaluated. The evaluation results are shown in Table 1.

  With respect to the polished test wafer after polishing, the remaining film thickness of the trench part / active part: 20 μm / 80 μm and 80 μm / 20 μm trench part is measured by the above-mentioned film thickness measuring apparatus, and the absolute value of the difference between the remaining film thicknesses at the two locations is obtained. It was defined as an index of wiring density dependence, and wiring density dependence was evaluated. The evaluation results are shown in Table 1. In addition, it is better that the wiring density dependency is small.

(Example 2 and Comparative Examples 1 to 3)
Similarly to Example 1, a cerium oxide polishing liquid was prepared so as to have the blending amount and pH shown in Table 1, and the polishing characteristics were evaluated. The evaluation results are shown in Table 1. From Table 1, it became clear that the polishing liquid provided by the present invention achieves the suppression of dishing and the dependency on the wiring density.

  DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Silicon nitride film, 3 ... Silicon oxide film, 4 ... Depth of trench of trench part, 5 ... Trench part silicon oxide film thickness after grinding | polishing, 6 ... Dishing amount, 100,200 ... Substrate.

Claims (7)

Containing particles containing cerium oxide, a leveling agent, an organic acid compound, a pH adjuster, and water;
The leveling agent is an acrylic acid polymer;
The organic acid compound is an organic compound having a sulfo group and an amino group,
Polishing liquid whose pH is 4.0 or more and 6.0 or less.   The polishing liquid according to claim 1, wherein the blending amount of the leveling agent is 0.01 to 1% by mass with respect to the total mass of the polishing liquid.   The polishing liquid according to claim 1 or 2, wherein the leveling agent is a homopolymer of acrylic acid or methacrylic acid.   The leveling agent is at least one selected from the group consisting of a copolymer of acrylic acid and methacrylic acid, and a copolymer of acrylic acid or methacrylic acid and another copolymerizable monomer. The polishing liquid according to claim 1 or 2.   The polishing liquid according to any one of claims 1 to 4, wherein the organic acid compound is 0.001 to 1% by mass relative to the total mass of the polishing liquid.   The polishing liquid according to claim 1, wherein the organic acid compound is at least one selected from 4-aminobenzenesulfonic acid (sulfanilic acid) and amidosulfuric acid (sulfamic acid).   A polishing method, wherein at least a part of an insulating material is removed by CMP using the polishing liquid according to claim 1.

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