JP2009290188A - Abrasive powder and polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide abrasive powder and polishing method employing the abrasive powder which polishes the projected part of a film to be polished, which incudes recesses and projections, at high speed and which reduces polishing scratch given to the film to be polished, in CMP technology employing ceria system abrasive powder. <P>SOLUTION: The abrasive powder contains at least four-valuent cerium oxide grain and four-valuent hydroxylate cerium grain as abrasive grain while containing at least water as a medium. In this case, the primary grain size of the cerium oxide grain and the primary grain size of the hydroxylate cerium grain are respectively not less than 1 nm and not more than 70 nm while the secondary grain size of the cerium oxide and the secondary grain size of the hydroxylate cerium grain in the abrasive powder are respectively not less than 10 nm and not more than 400 nm. In the polishing method, a film to be polished is polished employing the abrasive powder. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an abrasive and a polishing method used for manufacturing a semiconductor device, and more particularly to an abrasive and a polishing method for planarizing a film to be polished formed on a substrate by chemical mechanical polishing.

  Semiconductor devices typified by large-scale integrated circuits (LSIs) achieve high performance by reducing circuit dimensions for each generation. For this reason, various high-precision processing techniques are required in the semiconductor device manufacturing process. Above all, planarization by chemical mechanical polishing (CMP) is indispensable for the current manufacturing process of semiconductor devices, forming shallow trench isolation, planarizing premetal insulating film and interlayer insulating film, contact plug and copper. Widely used for forming damascene wiring.

  In general, in a CMP process, polishing is performed by sliding a semiconductor substrate on which a film to be polished is pressed against a polishing pad while sliding each other. At this time, a polishing agent is continuously dropped onto the polishing pad, and this polishing agent is an important factor that determines CMP characteristics such as polishing rate, flatness, and defect density of a film to be polished. In particular, the CMP characteristics change greatly by changing the type and concentration of abrasive grains contained in the abrasive.

  The most commonly used abrasive for CMP is an abrasive containing silica abrasive such as fumed silica or colloidal silica. Silica-based abrasives are characterized by high versatility, and a wide variety of films can be polished regardless of whether they are insulating films or conductive films by appropriately selecting the abrasive concentration, pH, additives, etc. .

  On the other hand, the application of abrasives containing ceria abrasive grains mainly for insulating films such as silicon oxide films is also expanding. A ceria-based abrasive is characterized in that it can polish a silicon oxide film at a high speed with a lower abrasive concentration than a silica-based abrasive. Further, it is known that if an appropriate additive is added to the ceria-based polishing agent, the flatness after polishing of the film to be polished can be improved, or selectivity can be imparted to the polishing rate of different films to be polished. . The ceria type abrasive | polishing agent used for CMP process is disclosed by patent document 1 or patent document 2, for example.

  However, on the other hand, when using a cerium oxide abrasive, it is not always easy to achieve both a high polishing rate and a few polishing scratches. In the case of cerium oxide, it is considered that processing proceeds due to the chemical action by the chemical activity of cerium oxide itself and the mechanical removal action as particles, and if the mechanical removal action by particles is strong, there is a tendency to cause polishing scratches .

In order to eliminate polishing scratches caused by particles in the abrasive, focusing on polishing with the chemical action of the particles and making the mechanical action as small as possible, particles of tetravalent metal hydroxide, or An abrasive containing any one of cerium compound particles having a density of ³ to 6 g / cm ³ and an average particle size of secondary particles of 1 to 300 nm is known. For example, tetravalent metal hydroxide particles When a blanket substrate made of a silicon oxide film is polished using a polishing agent containing only silicon, it is shown that there are no polishing flaws by observation with an optical microscope (see Patent Document 3).

JP-A-8-22970 Japanese Patent Laid-Open No. 10-106994 Republished patent WO2002 / 067309

  As circuit dimensions of semiconductor devices become finer, polishing scratches generated in the CMP process have become a serious problem. In order to solve this problem, attempts have been made to reduce the polishing scratches by reducing the primary particle size of the abrasive grains as described in Patent Document 3, but along with recent technological advances, Further, there is a demand for reduction of polishing scratches at a high level.

  If the primary particle size of the abrasive grains is reduced, polishing flaws tend to be reduced, but at the same time the mechanical action is also reduced. For this reason, a so-called blanket substrate with no irregularities on the surface can be polished, but a new problem arises that the polishing rate of the projections of the so-called pattern substrate with irregularities on the surface (hereinafter referred to as the pattern polishing rate) decreases. I found out that For example, the polishing agent described in Patent Document 3 describes that the polishing rate for the blanket substrate (hereinafter, blanket polishing rate) is good, but does not mention the polishing rate for the pattern substrate at all.

  In addition, when the ratio of the pattern polishing rate to the blanket polishing rate decreases due to the decrease in the pattern polishing rate, the variation in the polishing rate due to the difference in pattern density of the film to be polished tends to increase. That is, when polishing a surface to be polished having a difference in pattern density within the same plane, the polishing amount varies depending on the location. Therefore, there is a demand for an abrasive that can be stably polished without depending on the pattern density.

This invention is made in view of the said problem, and makes it a subject to achieve the following objectives.
SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing agent capable of polishing a convex portion of a film to be polished having irregularities at a high speed and reducing polishing scratches on the film to be polished in a CMP technique using a ceria-based polishing agent. It is providing the grinding | polishing method using this.
Another object of the present invention is to provide a polishing agent capable of reducing the difference in polishing amount depending on the location when polishing a surface to be polished having a difference in pattern density, and a polishing method using this polishing agent. There is to do.

The above problems are solved by the present invention described below.
(1) An abrasive containing at least tetravalent cerium oxide particles and tetravalent cerium hydroxide particles as abrasive grains, and containing at least water as a medium,
The primary particle size of the cerium oxide particles is 1 nm or more and 70 nm or less,
The primary particle size of the cerium hydroxide particles is 1 nm or more and 70 nm or less,
A polishing agent, wherein a secondary particle size of the cerium oxide particles and a secondary particle size of the cerium hydroxide particles in the polishing agent are 10 nm or more and 400 nm or less, respectively.

(2) The abrasive according to (1), wherein the cerium hydroxide particles are contained in an amount of 5% by weight to 95% by weight with respect to the total amount of the abrasive grains.

(3) The abrasive according to (1) or (2), wherein the abrasive grains are contained in an amount of 0.01% by weight to 10% by weight with respect to the abrasive.

(4) The abrasive according to any one of (1) to (3), wherein the cerium hydroxide particles are obtained by mixing a tetravalent cerium salt and an alkali solution.

(5) The abrasive according to any one of (1) to (4), further comprising an additive.

(6) A two-component abrasive obtained by dividing the abrasive according to (5) into a slurry containing at least the abrasive grains and an additive containing at least the additive.

(7) The substrate on which the film to be polished is formed is pressed against the polishing pad and pressurized, and the abrasive according to any one of (1) to (5) is supplied between the film to be polished and the polishing pad. A polishing method comprising polishing a film to be polished by sliding a substrate and a polishing pad relative to each other.

(8) The substrate on which the film to be polished is formed is pressed against the polishing pad and pressurized, and then supplied between the film to be polished and the polishing pad in a state where the two-component abrasive described in (6) above is mixed. A polishing method comprising polishing a film to be polished by sliding a substrate and a polishing pad against each other.

  According to the present invention, in a CMP process using a ceria-based polishing agent, it is possible to polish a convex portion of a film to be polished having irregularities at high speed while achieving reduction of polishing scratches on the film to be polished. Further, it is possible to provide an abrasive having a large ratio of the pattern polishing rate to the blanket polishing rate and a small rate of fluctuation of the polishing rate due to the presence / absence ratio of the unevenness of the film to be polished. As a result, the throughput of the CMP process can be improved, and the yield of semiconductor devices can be improved by reducing defects resulting from the CMP process.

<Abrasive>
The abrasive of the present invention is an abrasive containing at least tetravalent cerium oxide particles and tetravalent cerium hydroxide particles as abrasive grains, and containing at least water as a medium, and the primary particle diameter of the cerium oxide particles is 1 nm or more and 70 nm or less, the primary particle diameter of the cerium hydroxide particles is 1 nm or more and 70 nm or less, the secondary particle diameter of the cerium oxide particles in the abrasive and the secondary particle diameter of the cerium hydroxide particles However, it is characterized by each being 10 nm or more and 400 nm or less.
Below, each component of this invention is explained in full detail.

(Abrasive grains)
In the abrasive of the present invention, the abrasive grains include at least tetravalent cerium oxide particles and tetravalent cerium hydroxide particles. In addition, other particles can be included as necessary to the extent that the effect of the abrasive of the present invention is not impaired.

(Tetravalent cerium oxide particles)
In general, tetravalent cerium oxide particles (hereinafter simply referred to as cerium oxide particles) are obtained by oxidizing cerium compounds such as carbonates, nitrates, sulfates and oxalates. As the oxidation method, firing or oxidation using hydrogen peroxide or the like can be used. In the case of firing, the firing temperature is preferably 350 ° C. or higher and 900 ° C. or lower. Moreover, a hydrothermal synthesis method can also be used as a method for producing cerium oxide particles. For example, the method of heating precursors, such as cerium hydroxide, in water at 100 degreeC or more can be mentioned.

  Commercially available ceria particles can also be used as the cerium oxide particles. Examples thereof include those sold by Nanophase Technologies, Ferro, Advanced Nano Products, Rhodia Electronics & Catalysis, CI Kasei Co., Ltd., and the like.

(Tetravalent cerium hydroxide particles)
In general, tetravalent cerium hydroxide particles (hereinafter simply referred to as cerium hydroxide particles) are obtained by a method in which a cerium salt and an alkali liquid are mixed to precipitate cerium hydroxide particles. This method is described in, for example, “Science of rare earth” (edited by Adachi Ginya, Kagaku Dojin, 1999), pages 304-305. As the cerium salt, for example, Ce (SO ₄ ) ₂ , Ce (NH ₄ ) ₂ (NO ₃ ) ₆ , Ce (NH ₄ ) ₄ (SO ₄ ) _{4 and the} like are preferable. As the alkaline solution, ammonia water, potassium hydroxide aqueous solution, sodium hydroxide aqueous solution or the like can be used. From the viewpoint of using the abrasive for semiconductor device production, aqueous ammonia containing no alkali metal is preferred. The cerium hydroxide particles synthesized by the above method can be washed to remove metal impurities. As a washing method, a method of repeating solid-liquid separation several times by centrifugation or the like can be used.
Moreover, since it uses for grinding | polishing which concerns on manufacture of a semiconductor device, it is preferable to suppress the content rate of an alkali metal and halogens to 10 ppm or less in a cerium hydroxide particle.

  In this invention, an abrasive grain is obtained by mixing a cerium oxide particle, a cerium hydroxide particle, and another particle as needed. At this time, there is no particular limitation on the mixing method, a method of mixing each dry powder, a method of mixing one of the other dry powders in a dispersion in which one of them is dispersed in a medium, a method of mixing each dispersion, etc. Can be mentioned.

  Further, a dispersion liquid of cerium oxide particles, a cerium salt, and an alkali liquid may be mixed to precipitate cerium hydroxide particles in the dispersion liquid of cerium oxide particles. Alternatively, the cerium hydroxide particles may be heated in water to convert part of the cerium hydroxide particles into cerium oxide particles.

  Further, the cerium oxide particles and the cerium hydroxide particles in the abrasive may or may not be bonded. In the case of bonding, the bonding form is not particularly limited, and examples thereof include covalent bond, van der Waals force, electrostatic attraction, dipole-dipole interaction, hydrophobic bond, and hydrogen bond.

  In the present invention, the abrasive grains may be mechanically pulverized in order to improve the dispersibility of the abrasive grains. As the pulverization method, dry pulverization using a jet mill or the like, or wet pulverization using a planetary bead mill or the like is preferable.

  Further, when the abrasive grains are dispersed in water, there is no particular limitation on the dispersion method. A homogenizer, an ultrasonic disperser, a wet ball mill or the like can be used in addition to the dispersion treatment with a normal stirrer. As the dispersion method and the particle size control method, for example, the method described in the complete collection of dispersion technologies (Information Organization, July 2005) can be used.

  The larger the primary particle size of the cerium oxide particles and cerium hydroxide particles, the higher the speed of polishing possible, but there is a tendency for polishing flaws to occur. Therefore, the primary particle diameters of the cerium oxide particles and the cerium hydroxide particles used in the present invention are 1 nm or more and 70 nm or less, respectively. When the primary particle size of at least one of the particles is smaller than 1 nm, there is a tendency that a practical polishing rate cannot be obtained, and when the primary particle size of any one of the particles is larger than 70 nm, polishing scratches become remarkable. Tend. The primary particle size is preferably 1 nm to 70 nm, more preferably 2 nm to 50 nm, and still more preferably 3 nm to 15 nm.

(Primary particle size)
In the present invention, primary particles refer to particles of a minimum unit corresponding to a crystallite observed when observed in a powder state with, for example, a transmission electron microscope (TEM). In the present invention, when a transmission electron microscope (TEM) photograph is taken and the primary particle is sandwiched between two parallel lines, the value of the portion with the smallest interval is the minor axis, the value of the largest portion is the major axis, The average of the minor axis and the major axis was defined as the crystallite grain size. And the particle size of 100 crystallites selected at random is measured, and the arithmetic average is taken as the primary particle size.

  The cerium oxide particles obtained by firing the cerium compound may form a polycrystal composed of a plurality of crystallites surrounded by crystal grain boundaries depending on the firing conditions. A polycrystalline body is different from an aggregate in which a plurality of primary particles are simply aggregated. In this case, the primary particle refers to one crystallite surrounded by a crystal grain boundary, not one polycrystal.

(Secondary particle size)
If the secondary particle size of the abrasive grains (aggregate particle size in the abrasive) is too small, the surface energy of the particles becomes high and the particles tend to aggregate. As a result, the secondary particle size fluctuates in the abrasive and the CMP characteristics such as the polishing rate tend to become unstable. Further, if the secondary particle size of the abrasive grains is too large, the weight of the particles increases and the particles tend to settle in the abrasive, and therefore the effective number of abrasive grains contributing to polishing tends to decrease and the polishing rate tends to decrease. There is.
Therefore, the secondary particle size of the abrasive grains used in the present invention is 10 nm or more and 400 nm or less. If the secondary particle size is 10 nm or more, a decrease in the stability of the secondary particle size can be suppressed in the abrasive, and if the secondary particle size is 400 nm or less, particles are precipitated in the abrasive. There is a tendency to be able to suppress. From such a viewpoint, the secondary particle size is preferably 40 nm or more and 300 nm or less, and more preferably 60 nm or more and 200 nm or less.

  In the present invention, the average particle size of the tetravalent metal hydroxide particles refers to Z-average Size obtained by cumulant analysis using a dynamic light scattering method. For example, Zetasizer Nano S (Malvern Instruments Co., Ltd.) can be used for the measurement, and the abrasive can be diluted with water to the extent that multiple scattering does not occur in the dynamic light scattering measurement. Specifically, for example, the abrasive is diluted with water so that the abrasive concentration is 0.05% by weight, the refractive index of the dispersion medium is 1.33, the viscosity is 0.887, and the measurement is performed at 25 ° C. And read the value displayed as Z-average Size.

(Content of cerium hydroxide particles)
In this invention, it is preferable that 5 weight% or more of cerium hydroxide particle | grains are contained with respect to the abrasive grain whole quantity at the point which can improve a pattern polishing rate. By containing 5% by weight or more of cerium hydroxide, the effect of accelerating the pattern polishing rate can be significantly obtained as compared with the case where cerium oxide particles are used alone. The content is more preferably 10% by weight or more, further preferably 15% by weight or more, and extremely preferably 20% by weight or more in that the pattern polishing rate is further improved.

When the cerium hydroxide particles are added, the pattern polishing rate tends to be accelerated as compared with the case where the cerium oxide particles are used alone. However, if the addition amount exceeds a certain amount, the pattern polishing rate is not further accelerated. Tend. Moreover, there is a tendency that the blanket polishing rate is gradually improved by increasing the addition amount of the cerium hydroxide particles. For this reason, when a large amount of cerium hydroxide particles is added, the ratio of the pattern polishing rate to the blanket polishing rate tends to be small.
In this respect, the content of the cerium oxide is preferably 95% by weight or less, more preferably 90% by weight or less, and 85% by weight or less with respect to the total amount of the abrasive grains. More preferably, it is particularly preferably 80% by weight or less, particularly preferably 75% by weight or less, and most preferably 70% by weight or less.

As a method for identifying the content of cerium hydroxide particles in the abrasive grains contained in the final abrasive, thermogravimetric analysis can be cited (see "Science of rare earths" above). For example, as disclosed in US Pat. No. 5,389,352, cerium oxide particles obtained by calcination of a cerium salt and cerium hydroxide obtained by mixing a cerium salt and an alkali solution at 40 ° C., respectively. Thermogravimetric analysis after drying for 15 hours. At this time, the weight loss up to 1000 ° C. is 3% by weight in the case of cerium oxide particles and 17 to 26% by weight in the case of cerium hydroxide particles. The chemical formula of the cerium hydroxide particles is expressed as Ce (OH) ₄ or CeO ₂ .2H ₂ O, and the difference in weight reduction from the cerium oxide particles is crystal water. For example, when cerium hydroxide particles are contained in an amount of 5% by weight with respect to the total amount of abrasive grains, the weight loss of the abrasive grains measured by the above method is 3.7 to 4.2% by weight, and the weight of cerium oxide particles alone. It can be distinguished from a decrease (3% by weight). For example, when 95 weight% of cerium hydroxide particles are contained with respect to the abrasive grains, the weight loss of the abrasive grains measured by the above method is 16.3 to 24.9 weight%, and the cerium hydroxide particles alone Distinguishable from weight loss (17-26% by weight).

  In the present invention, the zeta potential of the abrasive grains in the polishing agent is preferably a positive potential. Thereby, the polishing speed of the convex part of the film to be polished having irregularities is increased as compared with the case where the zeta potential during polishing of the abrasive grains is a negative potential. For the zeta potential measurement, for example, the brand name Zeta Sizer 3000HS (Malvern Instruments Co., Ltd.) can be used, and the abrasive is diluted with water so that the amount of scattered light (500 to 2000 KCts) recommended for Zeta Sizer 3000HS is measured. can do.

(Other particles)
On the other hand, particles other than cerium oxide particles and cerium hydroxide particles can be included as abrasive grains, and the particles include inorganic particles such as silica particles, alumina particles, titania particles, zirconia particles, diamond particles, and carbon particles. And organic resin particles such as urethane resin particles, acrylic resin particles, methacrylic resin particles, styrene resin particles, and epoxy resin particles.
When other abrasive grains are contained, the content is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, and more preferably 15 to 85% by weight with respect to the total amount of the abrasive grains. More preferably.

  If the concentration of the abrasive grains in the abrasive is too low, the polishing rate is low, and if it is too high, the particles tend to aggregate and the polishing rate tends to decrease. Therefore, the content of the abrasive grains is preferably 0.01% by weight or more and 10% by weight or less, more preferably 0.05% by weight or more and 5% by weight or less, and more preferably 0.1% by weight or more and 1% by weight or less. More preferably, it is less than wt%.

(Medium)
In the abrasive of the present invention, the medium contains at least water. Further, if necessary, a medium other than water can be contained. Specifically, for example, methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, t-butyl In addition to alcohols such as alcohol and hydrocarbons such as hexane, cyclohexane and heptane, ethers, ketones, esters and the like can be mentioned.

(Abrasive pH)
In the present invention, the pH of the abrasive is preferably 3.0 to 9.0 in that a good polishing rate can be obtained and the aggregation of particles can be suppressed. In terms of excellent polishing rate, the pH is more preferably 4.0 or more, and even more preferably 5.0 or more. Further, the pH is more preferably 8.0 or less, and even more preferably 7.0 or less, from the viewpoint of easily suppressing particle aggregation.

  The pH can be adjusted with a known pH adjusting agent. Although it does not specifically limit as a pH adjuster, The thing which can mainly contribute to adjustment of pH and does not have a bad influence on a grinding | polishing characteristic is preferable. From such a viewpoint, examples of the pH adjuster include acids such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, and boric acid, and alkaline components such as ammonia, sodium hydroxide, tetramethylammonium hydroxide, and imidazole. . A buffer may be added to stabilize the pH. Examples of such a buffer solution include an acetate buffer solution and a phthalate buffer solution.

  The pH of the abrasive can be measured by a pH meter using a general glass electrode. Specifically, for example, Model pH81 manufactured by Yokogawa Electric Corporation was used. Use phthalate pH buffer solution (pH 4.21) and neutral phosphate pH buffer solution (pH 6.86) as standard buffers, calibrate the pH meter at two points, and then place the pH meter electrode in the abrasive. Then, it can be obtained by measuring the value after 2 minutes or more has passed and stabilized. At this time, the liquid temperature of the standard buffer solution and the abrasive can be set to 25 ° C., for example.

(Additive)
In the present invention, the abrasive may contain an additive. Here, the additive refers to a substance contained in addition to the abrasive grains and the medium. By adding an additive, the dispersibility and storage stability of the abrasive can be adjusted. In addition, the polishing characteristics can be adjusted, such as improving the polishing rate of the film to be polished, improving the flatness after polishing, and imparting selectivity to the polishing rate of different films to be polished. Note that an acid component or an alkali component for adjusting the pH of the abrasive can also be regarded as an additive.

  The additive used in the present invention may be a monomer or a polymer, and may be used alone or in combination. The addition amount of these additives is preferably 0.01% by weight or more and 30% by weight or less with respect to the abrasive. Usually, when the addition amount is too small, it is difficult to obtain a sufficient effect of adjusting the polishing characteristics, and when the addition amount is too large, the particles tend to settle.

  Examples of the additive that is a monomer include carboxylic acid, amino acid, amphoteric surfactant, anionic surfactant, nonionic surfactant, and cationic surfactant. .

  The carboxylic acid is not particularly limited as long as it has solubility in water, and examples thereof include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and lactic acid.

  Examples of the amino acid include arginine, lysine, aspartic acid, glutamic acid, asparagine, glutamine, histidine, proline, tyrosine, tryptophan, serine, threonine, glycine, alanine, β-alanine, methionine, cysteine, phenylalanine, leucine, valine, An isoleucine is mentioned.

  Examples of the amphoteric surfactant include betaine, β-alanine betaine, lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, amidopropyl laurate. Examples include betaine, coconut oil fatty acid amidopropyl betaine, and lauryl hydroxysulfobetaine.

  Examples of the anionic surfactant include lauryl sulfate triethanolamine, ammonium lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and a special polycarboxylic acid type polymer dispersant.

  Examples of the nonionic surfactant include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether, polyoxyethylene Ethylene nonylphenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxy Ethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, tetraoleic acid polio Siethylene sorbit, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2-hydroxyethyl methacrylate, alkylalkanolamide Etc.

  Examples of the cationic surfactant include coconut amine acetate and stearylamine acetate.

  Of these additives, carboxylic acids, amino acids, and amphoteric surfactants are preferable from the viewpoint of excellent dispersibility and polishing rate. Furthermore, an amphoteric surfactant is more preferable in terms of excellent stability of the abrasive, and betaine, β-alanine betaine, and amidopropyl betaine laurate are particularly preferable.

  As an additive, a water-soluble polymer can be used to improve the polishing rate. Specifically, for example, polysaccharides such as alginic acid, pectinic acid, carboxymethylcellulose, agar, curdlan and pullulan; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, polyfumaric acid (P-styrene carboxylic acid), polyamic acid ammonium salt, polyamic acid sodium salt, polycarboxylic acid such as polyglyoxylic acid and salts thereof; vinyl polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyacrolein; polyacrylamide, polydimethyl Examples thereof include acrylic polymers such as acrylamide, polyethylene glycol, and the like. The molecular weight of these water-soluble polymers is preferably 500 or more.

  The molecular weight of the water-soluble polymer can be measured using a static light scattering method. Specifically, for example, using Zetasizer Nano (Malvern Instruments), the amount of scattered light of samples having different concentrations can be measured. And a Debye plot can be prepared and obtained. At this time, the refractive index concentration increment (dn / dC) can be measured using a differential refractometer (Otsuka Electronics DRM-3000). In any measurement, water is used at 25 ° C. as a solvent.

  In the present invention, the method for storing the abrasive is not particularly limited. You may preserve | save as 1 liquid type abrasive | polishing agent containing an abrasive grain, water, and an additive as needed. Further, for example, it may be divided into a slurry containing at least abrasive grains (hereinafter simply referred to as slurry) and an additive solution containing at least an additive and stored as a two-component abrasive. In any case, it may be stored as a concentrated abrasive, concentrated slurry, or concentrated additive solution with reduced water content and diluted with water during polishing.

  When polishing using a one-part abrasive containing abrasive grains, water, and, if necessary, an additive, as a method for supplying the abrasive, for example, a method of feeding and supplying the abrasive directly, concentrated polishing For example, a method of feeding the agent and water through separate pipes, joining them, mixing them and supplying them, a method of mixing concentrated abrasives and water in advance, and supplying them can be used.

  In the case of a two-component abrasive in which the abrasive grains and the additive solution are separated, the polishing characteristics can be adjusted by arbitrarily changing the composition of these two components. When polishing using a two-component abrasive, for example, a method of supplying the abrasive is a method in which the slurry and the additive liquid are fed through separate pipes, and these pipes are joined and mixed to be supplied. be able to. Further, it is also possible to use a method in which a concentrated slurry, a concentrated additive solution, and water are fed through separate pipes, and these are joined and mixed to be supplied. Further, a method of supplying a mixture of slurry and additive solution in advance can be used. Furthermore, a method of supplying a premixed slurry, concentrated additive solution, and water can be used.

  As described above, when a one-component concentrated abrasive is used, the secondary particle size of the abrasive grains in the concentrated abrasive is preferably 10 nm or more and 400 nm or less. This makes it easy to control the secondary particle size of the abrasive grains in the abrasive to 10 nm or more and 400 nm or less when the concentrated abrasive is diluted with water to adjust the abrasive.

  Similarly, also when it is set as a 2 liquid type abrasive | polishing agent, it is preferable that the secondary particle size of the abrasive grain in a slurry or concentrated slurry is 10 nm or more and 400 nm or less. In this way, when the slurry or concentrated slurry is mixed with the additive solution, the concentrated polishing solution, and water to adjust the polishing agent, the secondary particle size of the abrasive grains in the polishing agent is 10 nm or more and 400 nm or less. Easy to control.

<Polishing method>
As a polishing method for polishing a film to be polished using the polishing agent of the present invention, a conventionally known method can be used. For example, the substrate having a film to be polished is pressed against a polishing surface plate to which a polishing cloth is attached so that the film to be polished and the polishing cloth are in contact with each other, and this embodiment is interposed between the film to be polished and the polishing cloth. There is a method of polishing a film to be polished by moving a substrate and / or a polishing surface plate while supplying the CMP abrasive according to the above. This method is particularly suitable for a polishing process in which a substrate having a step on the surface is polished, thereby flattening the step.

  In the present invention, a polishing apparatus that can be used is not particularly limited, and a general polishing apparatus having a substrate holder capable of holding a substrate and a polishing surface plate to which a polishing pad can be attached can be used. A motor or the like whose rotation speed can be changed is attached to each of the substrate holder and the polishing surface plate. For example, EPO-111, EPO-222, FREX-200, FREX-300 manufactured by Ebara Manufacturing Co., Ltd., MIRRA, Reflexion manufactured by Applied Materials, etc. can be used as the polishing apparatus.

  The conditions for polishing by these polishing apparatuses are not particularly limited, but the rotation speed of the surface plate is preferably 200 rpm or less, and the pressure (polishing load) applied to the substrate is preferably 100 kPa or less so that the substrate does not come off the substrate holder. Moreover, there is no restriction | limiting in particular in the abrasive | polishing agent supply amount on a polishing pad, However, It is preferable that the surface of a polishing pad is always covered with the abrasive | polishing agent.

  In the present invention, the polishing pad that can be used is not particularly limited, and general nonwoven fabrics, non-foamed resins, foamed resins, porous resins, and the like can be used. Further, it is preferable that the polishing pad is subjected to groove processing so that an abrasive is accumulated.

  The material of the polishing pad is not particularly limited, and polyamides such as polyurethane, acrylic, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly-4-methylpentene, cellulose, cellulose ester, nylon, and aramid are used. Resin such as polyimide, polyimide amide, polysiloxane copolymer, oxirane compound, phenol resin, polystyrene, polycarbonate, epoxy resin can be used.

  The surface of the polishing pad is preferably always in the same state even if the number of polishings is increased. For this reason, it is preferable to condition the polishing pad during polishing or after each polishing. For example, it can be conditioned using a dresser with diamond particles.

  The substrate after polishing is preferably washed well to remove particles adhering to the substrate. In addition to pure water, dilute hydrofluoric acid or ammonia water may be used in combination for cleaning, or a brush may be used in combination to increase cleaning efficiency. Further, after washing, it is preferable to dry after removing water droplets adhering to the substrate using a spin dryer or the like.

  The abrasive and the polishing method of the present invention can be widely applied to processes that require planarization of a film to be polished in the manufacture of semiconductor devices. For example, the present invention can be applied to a process for planarizing an insulating film for shallow trench isolation, a premetal insulating film, an interlayer insulating film, a process for forming a contact plug or a copper damascene wiring, and the like. In such a flattening step, the unevenness of the film to be polished is eliminated by the polishing method of the present invention, and a smooth surface is obtained over the entire surface of the substrate.

  There is no particular limitation on the film forming method that can be polished by the polishing agent and polishing method of the present invention, such as chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, coating method, thermal oxidation method, plating method and the like. Can be used.

  The material of the film to be polished is not particularly limited, and an insulating film, a semiconductor, and a metal can be polished. Among these, the polishing agent of the present invention can achieve both excellent polishing rate and suppression of polishing scratches in applications where a film to be polished containing a silicon compound is polished. Specific examples of silicon compounds include silicon insulating films such as silicon oxide films and silicon nitride films.

  Examples of silicon compound polishing films include amorphous silicon films, polysilicon films, silicon germanium films, metal silicide films, silicon oxide films, silicon nitride films, silicon carbide films, silicon oxynitride films, silicon carbonitride films, Examples thereof include a silicon carbonate film.

  As a method for forming a silicon oxide film, for example, a thermal CVD method in which monosilane and oxygen are thermally reacted, a quasi-atmospheric pressure CVD method in which tetraethoxysilane and ozone are thermally reacted, monosilane and nitrogen dioxide (or tetraethoxysilane and oxygen). A plasma CVD method in which a plasma reaction is performed, and a coating method in which a liquid raw material containing inorganic polysilazane, inorganic siloxane, or the like is applied onto a substrate. The silicon oxide film obtained by the method as described above may contain elements other than silicon and oxygen, such as hydrogen, boron, phosphorus, and carbon. Can be adjusted. Further, in order to stabilize the film quality of the silicon oxide film obtained by the above method, heat treatment may be performed at a temperature of 150 ° C. to 1000 ° C. as necessary after the film formation.

  As a method for forming a silicon nitride film, for example, a low pressure CVD method in which dichlorosilane and ammonia are thermally reacted, a plasma CVD method in which monosilane, ammonia and nitrogen are subjected to plasma reaction, and the like can be given.

  Examples of films to be polished other than silicon-based compounds include, for example, high dielectric constant films such as hafnium-based, titanium-based, and tantalum-based oxides, metal films such as copper, aluminum, tantalum, titanium, tungsten, and cobalt, germanium, Semiconductor films such as gallium nitride, gallium phosphide, gallium arsenide, organic semiconductors, phase change films such as germanium, antimony, and tellurium, inorganic conductive films such as indium tin oxide, polyimides, polybenzoxazoles, acrylics, and epoxys And a phenolic polymer resin film.

  The polishing agent and polishing method of the present invention are not limited to polishing film materials, and include various types such as glass, silicon, silicon carbide, silicon germanium, germanium, gallium nitride, gallium phosphide, gallium arsenide, sapphire, and plastic. It can also be applied to polishing of substrate material. Furthermore, the polishing agent and polishing method of the present invention are not limited to the production of semiconductor devices, but include image display devices such as liquid crystal and organic EL, photomasks, lenses, prisms, optical fibers, optical components such as single crystal scintillators, It can also be applied to the manufacture of optical storage elements such as optical switching elements, optical elements such as optical waveguides, light emitting elements such as solid state lasers and blue laser LEDs, magnetic disks, and magnetic heads.

(Measurement of polishing scratches)
The abrasive | polishing agent of this invention can make compatible the effect of suppression of a high grinding | polishing speed and a grinding | polishing damage | wound as demonstrated so far. Here, the polishing flaw is conventionally observed visually or with an optical microscope. Since the average magnification of the optical microscope is about 500 times, the size of the flaw observed as a clear flaw is at most. The order was several tens of μm.

  The abrasive of the present invention can reduce not only scratches of the size of several tens of μm but also fine scratches observed using a scanning electron microscope, for example, scratches of 0.2 μm or more. The number can be reduced. The number of scratches of 0.2 μm or more is preferably 20 or less, more preferably 10 or less, per 8 inch wafer. Although the detection limit of the scanning electron microscope is several tens of nm, it can be said that it is sufficient to detect a scratch of 0.2 μm or more from the viewpoint of measurement accuracy and characteristics.

  When measuring such a fine polishing flaw, a scanning electron microscope type defect inspection apparatus can be used, for example, SEMVision of Applied Materials can be used. Specifically, for example, the surface of the blanket evaluation substrate or pattern evaluation substrate after polishing is scanned with a laser to detect the position and size of the defect. Next, the minimum defect size to be detected is input to the apparatus, and a defect having a size larger than that is photographed with a scanning electron microscope. For example, if the thickness is 0.2 μm, all defects having a size of 0.2 μm are photographed on the image. However, not all of the photographed defects are polishing scratches, and foreign particles or abrasive grains in the abrasive may remain. Since the image of the photographed defect can be seen on the monitor, it is visually confirmed whether it is a scratch or a foreign object, and only the number of scratches is counted. In rare cases, there may be a defect that cannot be identified as a flaw or a foreign object even when the image is viewed. In that case, if the defect is observed with an electron microscope from three directions, three-dimensional information of the defect can be obtained. If it is concave with respect to the substrate to be polished, it is a polishing flaw, and if it is convex, it is not a flaw.

(Example 1)
(Preparation of abrasive)
Nanotek Ceria (trade name, hereinafter referred to as cerium oxide particle A), which is a commercially available cerium oxide particle, was mixed with water to prepare a suspension of 0.5% by weight of cerium oxide particle A. . When the powder obtained by sufficiently drying this suspension was observed with a TEM, the primary particle diameter of the cerium oxide particles was 14 nm.

Separately, 430 g of Ce (NH ₄ ) ₂ (NO ₃ ) ₆ was dissolved in 7300 g of pure water, and then 240 g of 25% by weight aqueous ammonia solution was mixed and stirred in this solution to obtain 160 g of cerium hydroxide. Particle B was obtained. The obtained cerium hydroxide particles B were subjected to solid-liquid separation by centrifugation (4000 rpm, 5 minutes). The liquid was removed, pure water was newly added, and centrifugation was again performed under the above conditions. Such an operation was repeated 5 times to wash the cerium hydroxide particles B. Finally, an appropriate amount of water was added to the cerium hydroxide particles B to obtain a suspension of 0.5 wt% cerium hydroxide particles B. When the powder obtained by sufficiently drying this suspension was observed with a TEM, the primary particle diameter of the cerium hydroxide particles B was 3 nm.

  The suspension of the cerium oxide particles A and the suspension of the cerium hydroxide particles B are mixed at a ratio of 4 to 1, and dispersed using an ultrasonic cleaner, and a 5 wt% aqueous ammonia solution is further added. The slurry 1 was added until the pH of the dispersion reached 6.0 to obtain an abrasive 1 containing 0.4 wt% cerium oxide particles and 0.1 wt% cerium hydroxide particles. In the abrasive 1, the cerium hydroxide particles are contained at 20% by weight with respect to the total amount of the abrasive grains.

  The abrasive 1 thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary grain size of the abrasive grains was used with Malvern Zeta Sizer 3000 Nano S. Was measured to be 85 nm. Further, the zeta potential was measured using a Malvern Zeta Sizer 3000HS and found to be +44 mV.

(Polishing evaluation)
A silicon substrate having a diameter of 200 mm was prepared, and a silicon oxide (SiO ₂ ) film having a thickness of 1000 nm was formed on the entire surface of the substrate by a plasma CVD method to obtain a blanket substrate on which the SiO ₂ film was formed. Hereinafter, this substrate is referred to as “SiO ₂ blanket evaluation substrate”.

Separately, a silicon substrate having a diameter of 200 mm was prepared, and a groove pattern having a groove width of 100 μm, a groove pitch of 200 μm, and a groove depth of 400 nm was formed on the entire surface of the substrate. For the formation of the groove pattern, well-known photolithography and dry etching were used as the semiconductor device manufacturing process. After the formation of the groove pattern, a SiO ₂ film having a thickness of 600 nm was formed on the entire surface of the substrate so as to fill the groove. In this way, a silicon substrate on which a SiO ₂ film having unevenness with a step of 400 nm was formed was obtained. Hereinafter, this substrate is referred to as “SiO ₂ pattern evaluation substrate”.

In the following, to a SiO ₂ film formed on the SiO ₂ blanket evaluation substrate is referred to as "blanket SiO ₂ film", the SiO ₂ film formed on the SiO ₂ pattern evaluation board "pattern SiO ₂ film " In Table 1, they are shown as SiO ₂ BTW and SiO ₂ PTW, respectively.

The SiO ₂ blanket evaluation substrate or the SiO ₂ pattern evaluation substrate was fixed to a substrate holder of a polishing apparatus (EPO-111 of Ebara Corporation). A polishing pad (IC-1000 manufactured by Rodel) made of porous urethane resin and having concentric grooves was attached to a polishing surface plate having a diameter of 600 mm. The substrate holder was pressed so that the evaluation substrate was in contact with the polishing pad, and the processing load was set to 30 kPa. While dropping the polishing agent on the polishing pad at a rate of 200 mL / min, the platen and the substrate holder were rotated at 50 rpm, respectively, and the evaluation substrate was polished for 60 seconds. After the polishing, the evaluation substrate was thoroughly washed with pure water and further dried.

Thereafter, the remaining film thickness of the blanket SiO ₂ film or the patterned SiO ₂ film was measured using an optical interference film thickness apparatus (Nanospec AFT-5100 manufactured by Nanometrics). Here, the reduction amount of the SiO ₂ film polished per unit time was defined as the polishing rate. Furthermore, using an optical microscope (Nikon ECLIPSE L200) and a scanning electron microscope type defect inspection device (Applied Materials SEMVision), the number of polishing scratches generated on the blanket SiO ₂ film or the patterned SiO ₂ film was measured. It was measured. Hereinafter, the polishing rate may be abbreviated as R / R.

As a result of the evaluation, when abrasive 1 was used, the polishing rate for the blanket SiO ₂ film was 680 nm / min, the polishing rate for the pattern SiO ₂ film was 480 nm / min for the convex portion, and 0 nm / min for the concave portion. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

(Example 2)
(Preparation of abrasive)
An experiment was conducted in which the content of the cerium hydroxide particles B in Example 1 was changed from 20 wt% to 60 wt%.
That is, a suspension of 0.5% by weight of cerium oxide particles A and a suspension of 0.5% by weight of cerium hydroxide particles B were prepared in the same manner as in Example 1.
The suspension of the cerium oxide particles A and the suspension of cerium hydroxide particles B were mixed at a ratio of 2 to 3, and dispersed using an ultrasonic cleaner to obtain slurry 2. A slurry 2 containing 0.2% by weight of cerium oxide particles and 0.3% by weight of cerium hydroxide particles is added to the slurry 2 until a pH of the dispersion reaches 6.0% by weight. Obtained. In the abrasive 2, the cerium hydroxide particles are contained by 60% by weight with respect to the total amount of the abrasive grains.
The abrasive 2 thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary particle size of the abrasive grains was used with a Malvern Zeta Sizer 3000 nano S. Was 81 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +46 mV. Similarly, slurry 2 was diluted so that the concentration of the abrasive grains was 0.05% by weight, and the secondary particle diameter of the abrasive grains was measured. The secondary particle size of the slurry 2 of slurry 2 was 77 nm.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the polishing agent is different, when the polishing agent 2 is used, the polishing rate of the blanket SiO ₂ film is 800 nm / min, and the polishing rate of the pattern SiO ₂ film is 450 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

(Example 3)
In Example 1, cerium oxide particles having a primary particle size of 14 nm were used, whereas in Example 3, cerium oxide particles having a primary particle size of 43 nm were used.
(Preparation of abrasive)
2 kg of cerium carbonate hydrate was calcined at 400 ° C. to obtain cerium oxide. 50 g of cerium oxide and 9950 g of pure water were mixed and pulverized and dispersed by a bead mill. Then, it filtered with a 1 micrometer membrane filter, and obtained the suspension of 0.5 weight% cerium oxide particle (henceforth cerium oxide particle C). When the powder obtained by sufficiently drying this suspension was observed with a TEM, the primary particle diameter of the cerium oxide particles was 43 nm.
On the other hand, a suspension of 0.5 wt% cerium hydroxide particles B was prepared in the same manner as in Example 1.
The suspension of the cerium oxide particles C and the suspension of the cerium hydroxide particles B are mixed at a ratio of 4 to 1, dispersed using an ultrasonic cleaner, and a 5 wt% aqueous ammonia solution is further added. The dispersion 3 was added until the pH of the dispersion reached 6.0 to obtain an abrasive 3 containing 0.4 wt% cerium oxide particles and 0.1 wt% cerium hydroxide particles. In the abrasive 3, the cerium hydroxide particles are contained at 20% by weight with respect to the total amount of the abrasive grains.
The abrasive 3 thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary particle size of the abrasive grains was used with a Malvern Zeta Sizer 3000 nano S. Was measured to be 93 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +45 mV.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the polishing agent was different, when the polishing agent 3 was used, the polishing rate of the blanket SiO ₂ film was 715 nm / min, and the polishing rate of the pattern SiO ₂ film was 485 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

Example 4
In Example 1, cerium oxide particles having a primary particle size of 14 nm were used, whereas in Example 4, cerium oxide particles having a primary particle size of 67 nm were used.
(Preparation of abrasive)
Cerium carbonate hydrate 2 kg was calcined at 425 ° C. to obtain cerium oxide. 50 g of cerium oxide and 9950 g of pure water were mixed and pulverized and dispersed by a bead mill. Then, it filtered with a 1 micrometer membrane filter, and obtained the suspension of 0.5 weight% cerium oxide particle (henceforth cerium oxide particle D). When the powder obtained by sufficiently drying this suspension was observed with a TEM, the primary particle diameter of the cerium oxide particles was 67 nm.
On the other hand, a suspension of 0.5 wt% cerium hydroxide particles B was prepared in the same manner as in Example 1.
The suspension of the cerium oxide particles D and the suspension of the cerium hydroxide particles B are mixed at a ratio of 4 to 1, dispersed using an ultrasonic cleaner, and a 5% by weight aqueous ammonia solution is further added. The dispersion 4 was added until the pH of the dispersion reached 6.0 to obtain an abrasive 4 containing 0.4 wt% cerium oxide particles and 0.1 wt% cerium hydroxide particles. In the abrasive 4, the cerium hydroxide particles are contained in an amount of 20% by weight with respect to the total amount of the abrasive grains.
The abrasive 4 thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary particle size of the abrasive grains was used with Malvern Zeta Sizer 3000 Nano S. Was 111 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +46 mV.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the polishing agent was different, when the polishing agent 4 was used, the polishing rate of the blanket SiO ₂ film was 740 nm / min, and the polishing rate of the pattern SiO ₂ film was 490 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

(Example 5)
An experiment was conducted in which the content of the cerium hydroxide particles B in Example 1 was changed from 20 wt% to 10 wt%.
(Preparation of abrasive)
In the same manner as in Example 1, a suspension of 0.5% by weight of cerium oxide particles A and a suspension of 0.5% by weight of cerium hydroxide particles B were prepared.
The suspension of the cerium oxide particles A and the suspension of cerium hydroxide particles B are mixed at a ratio of 45: 5 and dispersed using an ultrasonic cleaner, and a 5% by weight aqueous ammonia solution is further added. The dispersion 5 was added until the pH of the dispersion became 6.0 to obtain an abrasive 5 containing 0.45 wt% cerium oxide particles and 0.05 wt% cerium hydroxide particles. In the abrasive 5, the cerium hydroxide particles are contained in an amount of 10% by weight with respect to the total amount of the abrasive grains.
The abrasive 5 thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary particle size of the abrasive grains was used with a Malvern Zeta Sizer 3000 nano S. Was measured to be 88 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +43 mV.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the polishing agent is different, when the polishing agent 5 is used, the polishing rate of the blanket SiO ₂ film is 645 nm / min, and the polishing rate of the pattern SiO ₂ film is 360 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

(Example 6)
An experiment was conducted in which the content of the cerium hydroxide particles B in Example 1 was changed from 20 wt% to 90 wt%.
(Preparation of abrasive)
In the same manner as in Example 1, a suspension of 0.5% by weight of cerium oxide particles A and a suspension of 0.5% by weight of cerium hydroxide particles B were prepared.
The suspension of the cerium oxide particles A and the suspension of the cerium hydroxide particles B are mixed at a ratio of 5 to 45, dispersed using an ultrasonic cleaner, and a 5 wt% aqueous ammonia solution is further added. The dispersion 6 was added until the pH of the dispersion reached 6.0 to obtain an abrasive 6 containing 0.05 wt% cerium oxide particles and 0.45 wt% cerium hydroxide particles. In the abrasive 6, the cerium hydroxide particles are contained in 90% by weight with respect to the total amount of the abrasive grains.
The abrasive 6 thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary particle size of the abrasive grains was used with Malvern Zeta Sizer 3000 nano S. Was 82 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +47 mV.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the abrasive was different, when the abrasive 6 was used, the polishing rate of the blanket SiO ₂ film was 820 nm / min, and the polishing rate of the pattern SiO ₂ film was 295 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

(Comparative Example 1)
An experiment was conducted in which the content of the cerium hydroxide particles B in Example 1 was changed from 20 wt% to 0 wt%. That is, the experiment was conducted with all abrasive grains as cerium oxide particles A.
(Preparation of abrasive)
A suspension of 0.5 wt% cerium oxide particles A was prepared in the same manner as in Example 1.
The suspension of the cerium oxide particles is dispersed with an ultrasonic cleaner, and 5% by weight of an aqueous ammonia solution is added until the pH of the dispersion becomes 6.0. An abrasive A containing In the abrasive A, the content of the cerium hydroxide particles is 0% by weight with respect to the total amount of the abrasive grains.
The polishing agent A thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary particle size of the abrasive grains was used with a Malvern Zeta Sizer 3000 nano S. Was measured to be 93 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +42 mV.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the polishing agent was different, when the polishing agent A was used, the polishing rate of the blanket SiO ₂ film was 610 nm / min, and the polishing rate of the pattern SiO ₂ film was 260 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

(Comparative Example 2)
An experiment was conducted in which the content of the cerium hydroxide particles B in Example 1 was changed from 20 wt% to 100 wt%. That is, the experiment was conducted using all abrasive grains as cerium hydroxide particles B.
(Preparation of abrasive)
A suspension of 0.5 wt% cerium hydroxide particles B was prepared in the same manner as in Example 1.
The above suspension of cerium hydroxide particles was dispersed with an ultrasonic cleaner, and 5% by weight aqueous ammonia solution was added until the pH of the dispersion reached 6.0. An abrasive B containing cerium particles was obtained. In the abrasive B, cerium hydroxide particles are contained in an amount of 100% by weight based on the total amount of the abrasive grains.
The abrasive B thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary grain size of the abrasive grains was used with a Malvern Zeta Sizer 3000 nano S. Was 77 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +48 mV.

(Polishing evaluation)
As a result of evaluating by the same method as in Example 1 except that the polishing agent was different, when the polishing agent B was used, the polishing rate of the blanket SiO ₂ film was 830 nm / min, and the polishing rate of the pattern SiO ₂ film was 240 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

(Comparative Example 3)
(Preparation of abrasive)
In the same manner as in Example 1, a suspension of 0.5% by weight of cerium oxide particles A and a suspension of 0.5% by weight of cerium hydroxide particles B were prepared.
The suspension of the cerium oxide particles A and the suspension of cerium hydroxide particles B were mixed at a ratio of 2 to 3, and dispersed manually by stirring with a stirring rod to obtain slurry C. A slurry C containing 0.2 wt% cerium oxide particles and 0.3 wt% cerium hydroxide particles was added to slurry C until 5 wt% aqueous ammonia solution was added until the pH of the dispersion reached 6.0. Obtained. In the abrasive C, the cerium hydroxide particles are contained in an amount of 60% by weight based on the total amount of the abrasive grains.
The abrasive C thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary grain size of the abrasive grains was used with Malvern Zeta Sizer 3000 Nano S. Was 440 nm. The zeta potential was measured using a Malvern Zeta Sizer 3000HS and found to be +39 mV. Similarly, the slurry C was diluted so that the concentration of the abrasive grains was 0.05% by weight, and the secondary particle diameter of the abrasive grains was measured. The secondary particle size of the slurry 2 of slurry 2 was 410 nm.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the polishing agent is different, when the polishing agent C is used, the polishing rate of the blanket SiO ₂ film is 330 nm / min, and the polishing rate of the pattern SiO ₂ film is 175 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope and a scanning electron microscope type defect inspection apparatus was zero.

(Comparative Example 4)
(Preparation of abrasive)
Cerium carbonate hydrate (2 kg) was calcined at 450 ° C. to obtain cerium oxide. 50 g of cerium oxide and 9950 g of pure water were mixed and pulverized and dispersed by a bead mill. Then, it filtered with a 1 micrometer membrane filter, and obtained the suspension of 0.5 weight% cerium oxide particle (henceforth cerium oxide particle E). When the powder obtained by sufficiently drying this suspension was observed with a TEM, the primary particle diameter of the cerium oxide particles was 83 nm.
The suspension of the cerium oxide particles E is dispersed with an ultrasonic cleaner, and 5% by weight of an acetic acid aqueous solution is added until the pH of the dispersion becomes 6.0. An abrasive D containing cerium particles was obtained. In the abrasive D, 0% by weight of cerium hydroxide particles is contained with respect to the total amount of abrasive grains.
The abrasive D thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary grain size of the abrasive grains was used with a Malvern Zeta Sizer 3000 nano S. Was measured to be 185 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +24 mV.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the polishing agent is different, when the polishing agent D is used, the polishing rate of the blanket SiO ₂ film is 720 nm / min, and the polishing rate of the pattern SiO ₂ film is 440 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope was zero. On the other hand, the polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using the scanning electron microscope type defect inspection apparatus were 33 and 25, respectively. At this time, the size of a typical scratch observed using a scanning electron microscope type defect inspection apparatus was 0.2 to 1 μm.

(Comparative Example 5)
(Preparation of abrasive)
A suspension of 0.5 wt% cerium oxide particles E was prepared in the same manner as in Comparative Example 4, and a suspension of 0.5 wt% cerium hydroxide particles B was prepared in the same manner as in Example 1. Prepared.
The suspension of the cerium oxide particles E and the suspension of the cerium hydroxide particles B are mixed at a ratio of 4 to 1, dispersed using an ultrasonic cleaner, and a 5 wt% aqueous ammonia solution is further added. The slurry E was added until the pH of the dispersion reached 6.0 to obtain abrasive E containing 0.4 wt% cerium oxide particles and 0.1 wt% cerium hydroxide particles. In the abrasive E, cerium hydroxide particles are contained in an amount of 20% by weight based on the total amount of the abrasive grains.
The abrasive E thus obtained was diluted with water so that the concentration of the abrasive grains was 0.05% by weight, and then the secondary grain size of the abrasive grains was used with a Malvern Zeta Sizer 3000 nano S. Was 128 nm. Further, the zeta potential was measured using Malvern Zeta Sizer 3000HS and found to be +46 mV.

(Polishing evaluation)
As a result of evaluation by the same method as in Example 1 except that the polishing agent is different, when the polishing agent E is used, the polishing rate of the blanket SiO ₂ film is 760 nm / min, and the polishing rate of the pattern SiO ₂ film is 495 nm / min at the convex portion. Minutes and 0 nm / min at the recess. Further, the number of polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using an optical microscope was zero. On the other hand, the polishing flaws of the blanket SiO ₂ film and the pattern SiO ₂ film observed using the scanning electron microscope type defect inspection apparatus were 28 and 22, respectively. At this time, the size of a typical scratch observed using a scanning electron microscope type defect inspection apparatus was 0.2 to 1 μm.

  Table 1 summarizes the results.

From Examples 1 to 6 and Comparative Examples 1 to 5, by using the predetermined cerium oxide particles and the predetermined cerium hydroxide particles in combination, polishing the pattern SiO ₂ film while keeping the polishing scratches of the film to be polished small It is clear that the speed can be increased. That is, in the polishing agents 1-2 and 5-6 in which the cerium oxide particles A and the cerium hydroxide particles B are used in combination, polishing is performed as compared with the polishing agents A and B using only the cerium oxide particles A or the cerium hydroxide particles B. The polishing rate of the patterned SiO ₂ film is improved while keeping few scratches. In particular, for the abrasives 1 to 5, the effect of increasing the ratio of the polishing rate of the pattern SiO ₂ film to the polishing rate of the blanket SiO ₂ film as compared with the polishing agents A and B of Comparative Examples 1 and 2 was also confirmed. Further, as is apparent from the evaluation results of the abrasives 3 to 4, even when the particle size of the cerium oxide particles of the abrasive 1 is changed within the scope of the present invention, the polishing scratches are small and the pattern SiO ₂ film is polished. It was confirmed that the rate was high and the ratio of the polishing rate of the pattern SiO ₂ film to the polishing rate of the blanket SiO ₂ film was large.
On the other hand, with respect to the polishing agent D in which the particle size of the cerium oxide particles of the polishing agent A was simply increased, the polishing rate of the pattern SiO ₂ film was improved as compared with the polishing agent A, but the polishing scratches increased. Similarly, for the polishing agent E in which the particle size of the cerium oxide particles of the polishing agent 1 was changed outside the scope of the present invention, the polishing rate of the pattern SiO ₂ film was improved as compared with the polishing agent 1, but the polishing scratches increased. did. From the above facts, it was confirmed that the polishing agent and the polishing method of the present invention can increase the pattern polishing rate while keeping few scratches.
FIG. 1 uses Examples 1 to 2 and 5 to 6 and Comparative Examples 1 and 2 to extract cerium oxide particles having the same primary particle size and cerium hydroxide particles having the same primary particle size, only in the mixing ratio. The relationship between the weight ratio of the cerium hydroxide particles and the polishing rate for the blanket SiO ₂ film and the patterned SiO ₂ film is plotted. Also from FIG. 1, it is clear that the polishing agent and polishing method of the present invention improve the pattern polishing rate.

And the polishing rate of the SiO ₂ film, illustrates graphically the relationship between the content ratio relative to the abrasive grains the total amount of cerium hydroxide particles.

Claims (8)

An abrasive containing at least tetravalent cerium oxide particles and tetravalent cerium hydroxide particles as abrasive grains and at least water as a medium;
The primary particle size of the cerium oxide particles is 1 nm or more and 70 nm or less,
The primary particle size of the cerium hydroxide particles is 1 nm or more and 70 nm or less,
A polishing agent, wherein a secondary particle size of the cerium oxide particles and a secondary particle size of the cerium hydroxide particles in the polishing agent are 10 nm or more and 400 nm or less, respectively.   The abrasive according to claim 1, wherein the cerium hydroxide particles are contained in an amount of 5 wt% to 95 wt% with respect to the total amount of abrasive grains.   The abrasive according to claim 1 or 2, wherein the abrasive is contained in an amount of 0.01 wt% to 10 wt% with respect to the abrasive.   The abrasive according to any one of claims 1 to 3, wherein the cerium hydroxide particles are obtained by mixing a tetravalent cerium salt and an alkali solution.   The abrasive according to any one of claims 1 to 4, further comprising an additive.   6. A two-component abrasive comprising: the abrasive according to claim 5 divided into a slurry containing at least the abrasive grains and an additive containing at least the additive.   The substrate on which the film to be polished is formed is pressed against the polishing pad and pressurized, and the substrate and the polishing are supplied while supplying the abrasive according to any one of claims 1 to 5 between the film to be polished and the polishing pad. A polishing method comprising polishing a film to be polished by sliding a pad against each other.   The substrate on which the film to be polished is formed is pressed against the polishing pad and pressurized, and the substrate is supplied while being supplied between the film to be polished and the polishing pad in a state where the two-component abrasive according to claim 6 is mixed. A polishing method comprising polishing a film to be polished by sliding the polishing pad against each other.

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