JP2011224751A - Cerium oxide abrasive and polishing method of substrate using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cerium oxide abrasive and a polishing method of a substrate using the same, keeping an appropriate polishing speed, reducing the occurrence of a scratch, and precisely polishing the surface of a semiconductor.SOLUTION: The cerium oxide abrasive contains cerium oxide particles formed by pulverizing cerium oxide obtained by firing a mixture of cerium carbonate with malonic acid, and water, with a central value of secondary particle size of the cerium oxide of 0.1-1 μm. The mixing ratio of malonic acid is 0.5-6 mol to 1 mol of cerium carbonate. The content of cerium oxide particles with a secondary particle size of 3 μm or more is 500 ppm or less in a solid.

Description

  The present invention relates to a cerium oxide abrasive and a method for polishing a substrate using the abrasive, and more particularly to a semiconductor planarization abrasive.

  Examples of applications that require precise polishing of the material surface include optical disks, magnetic disks, glass substrates for flat panel displays, watch plates, camera lenses, glass materials used in various lenses for optical components, filters, etc. There are crystal materials, substrates such as semiconductor silicon wafers, insulating films, metal layers, barrier layers and the like formed in each process of semiconductor device manufacturing.

  The surface of these materials is required to be polished with high accuracy. As a polishing process in semiconductor device manufacturing, for example, planarization of an interlayer insulating film such as a silicon oxide film, or a shallow trench excluding an extra silicon oxide film embedded on a substrate to isolate an element in an integrated circuit There are element isolation and the like.

  As a polishing agent for precision polishing in these semiconductor device manufacturing, especially a silica polishing agent using silica fine particles as polishing particles is widely used because scratches on the surface to be polished are small, but the polishing rate is low. In recent years, a cerium oxide abrasive containing cerium oxide having a high polishing rate has attracted attention (see, for example, Patent Document 1 and Patent Document 2).

JP 2000-26840 A JP-A-2-371267

  However, the cerium oxide abrasive described above has a problem that it has more polishing scratches (hereinafter referred to as “scratch”) than the silica abrasive.

  Cerium oxide abrasives have been used for glass polishing for a long time, but in order to apply to semiconductor planarization, it was necessary to avoid contamination with impurities as much as possible. Therefore, the rare earth material is once purified to obtain high-purity cerium oxide via a cerium salt. As the cerium salt, cerium carbonate, cerium oxalate, cerium nitrate and the like are used. These cerium salts were calcined, and the pulverized cerium oxide was dispersed to produce a semiconductor planarizing abrasive.

  Scratches generated in the polishing process tend to be reduced by lowering the content of large-diameter particles in the abrasive, but cerium compounds such as cerium carbonate, which have been used in the production of cerium oxide, are fired. In the method of pulverization, the pulverization takes a long time, the parts of the pulverizer are worn, and the possibility that the abrasion powder is mixed in the abrasive increases. This abrasion powder causes an abrasion flaw and is not preferable.

  Further, in a short pulverization, the large particle size particles remain without being pulverized and are mixed in the abrasive, and therefore it is difficult to reduce the content of the large particle size particles.

  On the other hand, as the integration of semiconductors has progressed, the processing dimensions of wiring and the like have been miniaturized to about 100 nm, and the demand for reducing defects such as scratches is increasing more and more, all of polishing speed, flattening, scratch reduction, etc. There is a demand for abrasives that satisfy the requirements.

  An object of the present invention is to provide a cerium oxide abrasive that can reduce the generation of scratches and precisely polish a semiconductor surface while maintaining an appropriate polishing speed, and a method for polishing a substrate using the abrasive. It is in.

  As a result of intensive studies on reducing scratches with a cerium oxide abrasive, the present inventor has found that cerium oxide is improved in grindability by mixing malonic acid with cerium carbonate and firing. By crushing this cerium oxide and using it as an abrasive, it shortens the pulverization time, prevents the mixing of wear powder from the pulverizer, and at the same time reduces the content of large particles, reducing scratches and flattening As a result, the inventors have found out that the present invention can be achieved.

That is, the present invention relates to the following.
(1) It contains cerium oxide particles obtained by firing a mixture of cerium carbonate and malonic acid, and water, and the median secondary particle diameter of the cerium oxide is 0.1 to 1 μm. A cerium oxide abrasive.
(2) The cerium oxide abrasive according to item (1), wherein the mixing ratio of malonic acid is 0.5 to 6 mol with respect to 1 mol of cerium carbonate.
(3) The cerium oxide abrasive according to item (1) or (2), wherein the content of cerium oxide particles having a secondary particle size of 3 μm or more is 500 ppm or less in the entire cerium oxide.
(4) The cerium oxide abrasive according to any one of items (1) to (3), further comprising a dispersant.
(5) The cerium oxide abrasive according to any one of items (1) to (4), wherein 99% by volume of the entire cerium oxide secondary particles have a particle size of 1 μm or less.
(6) Using the cerium oxide abrasive according to any one of items (1) to (5) and supplying a polishing liquid between the substrate having the film to be polished and the polishing cloth, the substrate is polished. A substrate polishing method for polishing a substrate having a film to be polished by applying pressure to the substrate and moving the film to be polished and a polishing cloth relatively.
(7) The method for polishing a substrate according to item (6), wherein the predetermined substrate is a semiconductor chip on which at least a silicon oxide film is formed.

  According to the present invention, the semiconductor surface in the wiring formation process can be polished at a high speed, and it is possible to reduce scratches with good flatness.

Hereinafter, embodiments of the present invention will be described in detail.
The abrasive of the present invention contains cerium oxide particles and water.
The cerium oxide particles described in the present invention are obtained by pulverizing cerium oxide obtained by firing a mixture of cerium carbonate and malonic acid. After pulverization, it is preferable to treat by sedimentation classification, filtration or the like, if necessary.
The mixing ratio of cerium carbonate and malonic acid is preferably 0.5 to 6 mol of malonic acid with respect to 1 mol of cerium carbonate.

Conventionally, in a method of firing a cerium salt such as cerium carbonate or cerium oxalate, which has been used for producing cerium oxide, cerium oxide is obtained by thermal decomposition of the cerium salt. In that case, there is often no significant difference between the shapes of the cerium salt and the cerium oxide.
However, when cerium carbonate and malonic acid are mixed and heated, a chemical reaction occurs between cerium carbonate and malonic acid, carbonate ions are replaced, and cerium oxide is obtained by thermal decomposition through the formation of cerium malonate. . This cerium oxide is greatly different in shape from cerium carbonate, and is also greatly different in shape from cerium oxide powder obtained by baking a commercially available cerium salt as it is, and becomes an aggregate of fine particles. Therefore, since this cerium oxide is an aggregate of fine particles, it is easily pulverized in a short time and becomes oxide fine particles.
That is, in the case of using malonic acid, it is easy to grind and the ratio of large particle diameter particles is small.

  In the present invention, the acid mixed with cerium carbonate is malonic acid. The form of malonic acid is not particularly limited, and examples include gas, solid, liquid, or solution state. Among them, solid is preferable from the viewpoint of handling, and the powder is more easily mixed with cerium carbonate. preferable. The size of the powder is not particularly limited. When malonic acid is a gas, it tends to be difficult to handle and mix with cerium carbonate. In addition, when malonic acid is in a liquid or solution state, the mixture with cerium carbonate becomes liquid and needs to be dried before heating to obtain an oxide, which tends to require time.

Although there is no restriction | limiting in the mixing method of the cerium carbonate and malonic acid in this invention, Since a carbon dioxide generate | occur | produces during mixing, the method of throwing both into the container which is not sealed and stirring is preferable. Depending on the mixing time, the shape of the oxide produced thereafter changes, but if mixed, the effect can be obtained regardless of the mixing time.
In addition, since malonic acid is used when mixing, it is preferable to use a corrosion-resistant resin or metal for the portion where the malonic acid of the mixing device comes into contact. It becomes easy to suppress that the part which dropped out falls and mixes.
Further, the cerium carbonate to be mixed contains moisture, has poor powder flowability, and has strong adhesion to the mixing device. Therefore, it is preferable to perform a polyfluorinated ethylene fiber coating treatment on the mixing device with improved flatness and good flatness of the mixing device because it also has corrosion resistance against malonic acid.

  The reaction between cerium carbonate and malonic acid proceeds sequentially in the mixed state using moisture contained in each other as a medium. Since it is a reaction between solids, it takes a long time to complete the reaction. When the reaction is not completed, cerium oxide having the same degree of grindability can be produced in different production lots by keeping the time until firing constant. Further, even when the reaction is not completed, mixing while heating under the same conditions (hereinafter referred to as “heat mixing”) evaporates moisture as a medium from the reaction system, and reacts at the end of heating and mixing. By making it no longer proceed, the degree of reaction progress can be made constant, thereby stably producing cerium oxide powder having the same degree of grindability regardless of the time until firing. it can.

  In addition, in order to stably produce a cerium oxide powder having the same level of grindability regardless of the time until firing, water must be removed from the reaction system after the reaction between cerium carbonate and malonic acid. Is preferred. It is preferable to completely remove moisture from the system. However, if the reaction stops in mixing and the reaction does not proceed from the mixing of cerium carbonate and malonic acid to the firing, moisture remains. The effect of the present invention can be obtained. That is, in the case of firing immediately after mixing, there is no problem if moisture is removed to such an extent that the reaction stops. Furthermore, it is possible to store without mixing immediately after mixing. In that case, when moisture is completely removed from the reaction system, the reaction does not proceed if moisture is not mixed during storage. When moisture remains in the reaction system, the temperature during mixing, the amount of moisture remaining, and the storage conditions (temperature) are important parameters for whether or not the reaction is stopped during storage. Also, even when moisture remains, it is important to keep the moisture from entering during storage.

  As a method for confirming that the reaction between cerium carbonate and malonic acid has stopped, there is a method for confirming the presence or absence of mass reduction with time of the mixture. Since carbon dioxide is generated as the reaction proceeds, the mass is reduced accordingly. If the mass has not decreased, it can be determined that the reaction has not progressed.

  As a method for determining whether or not there is a mass decrease, it can be determined by measuring the mass of the mixture immediately after the end of mixing and the mass of the mixture immediately before performing the firing, and measuring the mass decrease amount therebetween. More specifically, it can be determined that the reaction has stopped when the mass loss after the mixture is left at a temperature of 25 ° C. for 24 hours is 0 to 0.1% by mass. In the present specification, the “mass of the mixture immediately after completion of mixing” is the mass measured in the range of 5 to 40 ° C. within 30 minutes after the completion of mixing.

Specific measurement methods include the following. That is, after mixing cerium carbonate and malonic acid, stopping the mixing apparatus to obtain a mixture (within 30 minutes), weigh about 1 to 100 g of the mixture.
Next, the mixture sample is left at a temperature of 25 ° C. for 24 hours, and the mass is measured again. Then, the mass reduction amount is obtained by calculation from the mass of the mixture immediately after completion of mixing and the mass of the mixture after standing for 24 hours.
The mass reduction amount of the mixture after standing for 24 hours thus obtained is preferably 0 to 0.1% by mass, more preferably 0 to 0.05% by mass, and 0 to 0.02% by mass. More preferably. If at least the mass reduction amount is 0.1 mass% or less, it can be determined that there is no mass reduction and the reaction has stopped.

Further, as another method for determining the presence or absence of mass loss, it can also be determined by sampling a small amount of the mixture, heating it to a temperature higher than the storage environment, and performing an accelerated test to determine whether a mass change occurs.
Specifically, for example, when the storage environment is 10 to 25 ° C., the mass of the mixed sample after evaporation of moisture is measured, and the sample is placed in a high-temperature bath or oven in a temperature 40 ° C. environment for 2 hours. Examples of the method include leaving it alone and measuring the mass again. Thereby, the presence or absence of mass reduction can be judged easily.
That is, if the “mass loss after standing at 40 ° C. for 2 hours” is 0 to 0.1 mass%, the “mass loss after standing at 25 ° C. for 24 hours” is also 0 to 0.1 mass. %, That is, it can be determined that the reaction has stopped.
However, when the “mass loss after standing at 40 ° C. for 2 hours” exceeds 0.1 mass%, it is necessary to confirm the mass reduction after leaving at 25 ° C. for 24 hours.

  If moisture is not completely removed from the reaction system, the reaction between cerium carbonate and malonic acid may or may not stop depending on the environment in which the mixture is stored. The reaction is more difficult to stop when the environment for storage is higher. For example, when storage is performed at room temperature, it is necessary to set the heating and mixing temperature in consideration of summer temperature conditions in an environment where there is a difference of about 30 ° C. in the atmospheric temperature, such as in summer and winter. In the heating and mixing step, when moisture is completely removed from the reaction system, the storage temperature and the heating and mixing temperature need not be taken into consideration. In any case, in this specification, it is determined that the reaction has stopped when the mass loss after the mixture is left at a temperature of 25 ° C. for 24 hours is 0 to 0.1 mass%.

The heating temperature at the time of firing described in the present invention is preferably 350 ° C. or higher, more preferably 400 ° C. to 1000 ° C., since the oxidation temperature of the cerium compound is 300 ° C.
In addition, the temperature increase rate at the time of baking is not specifically limited.
Firing can be performed using a batch furnace, a rotary kiln, a tunnel furnace, or the like.

The cerium oxide particles produced by the above method can be pulverized by dry pulverization using a jet mill or the like, or wet pulverization using a planetary bead mill or the like. When pulverizing by dry pulverization, the temperature rise in the pulverization equipment is less likely to occur, and when pulverizing by wet pulverization, fine particles in the cerium oxide particles are less likely to adhere to the pulverization equipment.
The jet mill is described, for example, in Chemical Industrial Papers, Vol. 6, No. 5, (1980), pages 527-532.

The abrasive of the present invention preferably has a composition further containing a dispersant in the cerium oxide particles and water. For example, it can be obtained by dispersing a composition containing cerium oxide particles and a dispersant prepared by the above method in water.
Although there is no restriction | limiting in the density | concentration of a cerium oxide particle, The range of 0.1-20 mass% is preferable from the ease of handling of a dispersion | distribution liquid abrasive | polishing agent.

  Since the dispersant is used for polishing semiconductor elements, it is preferable to suppress the content of alkali metals such as sodium ions and potassium ions and halogen to 10 ppm or less in the cerium oxide particles, for example, a salt of polyacrylic acid A salt of a copolymer of acrylic acid and methacrylic acid is preferred, and the salt is preferably an ammonium salt. More specifically, a polymer dispersant such as ammonium polyacrylate is preferable.

  The amount of the dispersant added is 0.01 to 5.0 parts by mass with respect to 100 parts by mass of the cerium oxide particles from the relationship between the dispersibility of the particles in the abrasive and the sedimentation prevention, and the relationship between the scratch and the additive amount of the dispersant. A range is preferred.

The weight average molecular weight of the dispersant is preferably from 100 to 50,000, and more preferably from 1,000 to 10,000. When the weight average molecular weight of the dispersant is less than 100, it is difficult to obtain a sufficient polishing rate when polishing the silicon oxide film or the silicon nitride film, and when the weight average molecular weight of the dispersant exceeds 50,000 This is because the viscosity tends to increase and the storage stability of the abrasive tends to decrease.
In the present invention, the weight average molecular weight is a value measured by gel permeation chromatography based on the following method and converted to standard polystyrene.

(Conditions for obtaining weight average molecular weight)
Sample: 10 μL
Standard polystyrene: Standard polystyrene manufactured by Tosoh Corporation (molecular weight: 190000, 17900, 9100, 2980, 578, 474, 370, 266)
Detector: manufactured by Hitachi, Ltd., RI-monitor, trade name “L-3000”
Integrator: Hitachi, Ltd., GPC integrator, product name “D-2200”
Pump: manufactured by Hitachi, Ltd., trade name “L-6000”
Degassing device: Showa Denko Co., Ltd., trade name "Shodex DEGAS"
Column: Hitachi Chemical Co., Ltd., trade names “GL-R440”, “GL-R430”, “GL-R420” connected in this order and used as eluent: tetrahydrofuran (THF)
Measurement temperature: 23 ° C
Flow rate: 1.75 mL / min Measurement time: 45 minutes

  As a method of dispersing these cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to a dispersion treatment using a normal stirrer.

  Since the secondary particle size of the cerium oxide particles in the abrasive thus prepared has a particle size distribution, 99% by volume (hereinafter referred to as “D99”) of the entire cerium oxide particles has a particle size of 1. It is preferably 0 μm or less. When D99 exceeds 1.0 μm, the generation of scratches increases. When D99 is 0.7 μm or less, scratches can be further reduced, which is further preferable.

  The median value of the secondary particle diameter of the cerium oxide particles (hereinafter also referred to as “D50”) is 0.1 to 1 μm, more preferably 0.1 to 0.5 μm, More preferably, it is 0.3 μm. This is because if the median value of the secondary particle diameter is less than 0.1 μm, the polishing rate tends to be slow, and if it exceeds 1 μm, polishing scratches are likely to occur on the surface of the film to be polished. The D50 of the secondary particle diameter of the cerium oxide particles in the abrasive and the D99 is a light scattering method, for example, a particle size distribution meter (for example, Master Sizermicroplus, refractive index: 1.9285 manufactured by Malvern Instruments, light source: He-Ne Laser, absorption: 0)).

  The content of coarse particles having a particle size of 3 μm or more in the entire solid in the abrasive is preferably small. In the present invention, the coarse particles of 3 μm or more mean particles captured by filtering with a filter having a pore diameter of 3 μm. The content of particles having a particle size of 3 μm or more occupying the entire solid in the abrasive is preferably 500 ppm or less in mass ratio, thereby increasing the effect of reducing scratches. When the content of particles of 3 μm or more in the entire solid is 200 ppm or less, the effect of reducing scratches is large and more preferable. When the content of particles of 3 μm or more in the entire solid is 100 ppm or less, the effect of reducing scratches is the largest and more preferable.

The coarse particle content of 3 μm or more can be determined by mass measuring particles captured by filtering with a filter having a pore diameter of 3 μm. The content of the entire solid in the abrasive is measured by drying the abrasive separately. For example, the residue obtained by drying 10 g of the abrasive at 150 ° C. for 1 hour is weighed to obtain the solid concentration. And the content of the whole solid can be obtained by multiplying the mass of the abrasive used for filtration with a filter having a pore diameter of 3 μm by the solid concentration.
Filtration and classification are possible as means for reducing the coarse particle content, but are not limited thereto.

A polymer additive that further improves the flatness and dispersibility can be added to the abrasive. Although it is not necessarily limited below, polymers, such as an acrylic ester derivative, acrylic acid, an acrylate, can be added, for example. Although the addition amount of a polymer additive is not specifically limited, 5-30 mass parts is preferable with respect to 100 mass parts of cerium oxide particles.
Acrylic acid is also used as the dispersant described above, but when acrylic acid is used as the polymer additive, the amount of acrylic acid added may be based on the amount of polymer additive added.

The weight average molecular weight of the polymer additive is preferably from 100 to 50,000, more preferably from 1,000 to 10,000. When the weight average molecular weight is 100 or more, a sufficient polishing rate can be obtained when polishing the SiO ₂ film or the silicon nitride film, and when the weight average molecular weight is 50,000 or less, the viscosity becomes high, This is because the storage stability of the polishing liquid is not lowered.

The abrasive preferably has a pH of 3 to 9, and more preferably 5 to 8. When the pH is 3 or more, the chemical action force is not too small and the polishing rate is not reduced. If the pH is 9 or less, the chemical action is too strong and the polished surface will not be dished (dishing).
The pH can be measured with a pH meter (for example, Model pH81 (trade name) manufactured by Yokogawa Electric Corporation). Specifically, after two-point calibration 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 value after the electrode is put into the polishing liquid and stabilized for 2 minutes or more is measured.

  The abrasive can also be prepared, for example, as a one-part abrasive composed of cerium oxide particles, a dispersant, a polymer additive, and water, and a cerium oxide slurry composed of cerium oxide particles, a dispersant, and water. It can also be prepared as a two-part abrasive that separates the additive consisting of a polymer additive and water. In either case, stable characteristics can be obtained.

  When the cerium oxide slurry and the additive liquid are stored as separate two-component abrasives, the planarization characteristics and the polishing rate can be adjusted by arbitrarily changing the blend of these two components. In the case of the two-pack type, the additive liquid and the cerium oxide slurry are sent at different flow rates through separate pipes, and these pipes are merged, that is, both are mixed immediately before the supply pipe outlet, and the polishing platen Either a method of supplying the sample at the top (immediate mixing method) or a method of supplying the two after mixing them in a container in advance (pre-mixing method) is used.

The polishing agent of the present invention presses the substrate against the polishing cloth while supplying the polishing agent between the polishing film formed on the substrate and the polishing cloth, so that the polishing film and the polishing cloth are relative to each other. And can be used for polishing to polish the film to be polished flat.
As a substrate, for example, a substrate related to a semiconductor device formation process, specifically, a substrate in which an inorganic insulating layer is formed on a semiconductor substrate at a stage where circuit elements are formed, or an inorganic insulation on a substrate in a shallow trench element separation formation process Examples include a substrate in which a layer is embedded. And as the said inorganic insulating layer which is a to-be-polished film | membrane, the insulating layer which consists of a silicon oxide film at least is mentioned.

  Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and comparative examples thereof, but the present invention is not limited to these examples.

Example 1
Cerium carbonate: 6 kg and malonic acid: 2.7 kg were placed in a polyethylene container having a vent hole, shaken with a shaker for 5 minutes, and mixed. This mixture was placed in an alumina container and baked in air at 800 ° C. for 2 hours to obtain 3 kg of a yellowish white powder. When this powder was subjected to phase identification by X-ray diffraction, it was confirmed to be cerium oxide.

The prepared cerium oxide: 1000 g, ammonium polyacrylate aqueous solution (40% by mass): 80 g, and deionized water: 5600 g were mixed and stirred for 10 minutes, and then bead mill (manufactured by Ashizawa Finetech Co., Ltd.) For 30 minutes. The obtained dispersion was allowed to settle at room temperature (25 ° C.) for 20 hours, and the supernatant was collected. This supernatant liquid is filtered through a filter with a pore size of 1.0 μm, and then filtered again with a filter of a pore size: 1.0 μm, and deionized water is added to adjust the solid content concentration to 5% by mass to flatten the semiconductor. A polishing agent was prepared.
In addition, the pore diameter used here: 1.0 μm filter uses a filter for mass production in which holes are formed by overlapping filter fibers, and the overlapped filters are not fixed to each other. Even if it exceeds 1.0 μm in diameter, it may pass through. Hereinafter, this type of filter is referred to as a “mass production filter”.

  The particle size of the obtained abrasive was measured using a laser diffraction particle size distribution analyzer (manufactured by Malvern Instruments, Mastersizer Micro Plus (trade name)), refractive index: 1.9285, light source: He—Ne laser. As a result of measuring the stock abrasive solution under the condition of absorption: 0, the median value of the secondary particle diameter (D50) was 190 nm, and D99 was 0.7 μm.

In order to examine the coarse particle content, the obtained abrasive was diluted 15 times, and 30 g was filtered with a 3 μm filter (a cyclopore track etch membrane filter manufactured by Whatman Corporation). After filtration, the filter was dried at room temperature (25 ° C.), the mass of the filter was measured, and the amount of coarse particles of 3 μm or more was determined from the mass increase before and after filtration. Separately, 10 g of this abrasive was dried at 150 ° C. for 1 hour, and the solid concentration in the abrasive was calculated. As a result, the amount of coarse particles (mass ratio) of 3 μm or more was 300 ppm in the solid.
Note that the filter with a pore diameter of 3 μm used here is a film type (single layer) in which holes are formed by laser processing, unlike a mass production filter, and captures all of those having a diameter exceeding 3 μm. Hereinafter, this type of filter is referred to as a “laser filter”.

  Moreover, the said abrasive | polishing agent was diluted 5 times with deionized water, and it grind | polished by the following method. The polishing rate was 650 nm / min. When the wafer surface was observed with an optical microscope, 20 scratches were observed on the entire surface of the 200 mm wafer.

(Polishing test method)
Polishing load: 30 kPa
Polishing pad: Rodel polyurethane foam resin (IC-1000 (trade name))
Number of revolutions: 75 platens / minute for surface plate, 75 revolutions / minute for pad, abrasive supply speed: 200 mL / minute Polishing object: Si wafer with P-TEOS film (200 mm)

(Example 2)
The cerium oxide prepared in Example 1: 1000 g, an aqueous solution of ammonium polyacrylate (40% by mass): 80 g, and deionized water: 5600 g were mixed and stirred for 10 minutes, and then bead mill (Ashizawa Finetech Co., Ltd.) For 30 minutes. The obtained dispersion was allowed to settle at room temperature (25 ° C.) for 100 hours, and the supernatant was collected. This supernatant liquid is filtered through a mass production filter having a pore size of 0.7 μm, and then filtered again through a filter having a mass production pore size of 0.7 μm, and deionized water is added to adjust the solid content concentration to 5% by mass. A flattening abrasive was prepared.

The particle size of the obtained abrasive was measured in the same manner as in Example 1. As a result, the median value (D50) of the secondary particle size was 160 nm and D99 was 0.5 μm.
In order to examine the coarse particle content, the amount of coarse particles of 3 μm or more was determined from the increase in mass before and after filtration with a laser filter in the same manner as in Example 1. As a result, the amount of coarse particles of 3 μm or more was 20 ppm in the solid.
Further, the above abrasive was diluted 5 times with deionized water and polished by the same polishing test method as in Example 1. The polishing rate was 350 nm / min. When the wafer surface was observed with an optical microscope, ten scratches were observed on the entire surface of the 200 mm wafer.

(Example 3)
6 kg of cerium carbonate and 4.1 kg of malonic acid were put in a polyethylene container with a hole for venting, shaken with a shaker for 12 hours, and mixed. This mixture was placed in an alumina container and baked in air at 800 ° C. for 2 hours to obtain 3 kg of a yellowish white powder. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide.

  The prepared cerium oxide: 1000 g, ammonium polyacrylate aqueous solution (40% by mass): 80 g, and deionized water: 5600 g were mixed and stirred for 10 minutes, and then bead mill (manufactured by Ashizawa Finetech Co., Ltd.) For 30 minutes. The obtained dispersion was allowed to settle at room temperature (25 ° C.) for 100 hours, and the supernatant was collected. The supernatant liquid is filtered through a mass production filter having a pore size of 0.7 μm, and then filtered again through a mass production filter having a pore size of 0.7 μm, and deionized water is added to adjust the solid content concentration to 5% by mass. A polishing abrasive was prepared.

The particle size of the obtained abrasive was measured in the same manner as in Example 1. As a result, the median value (D50) of the secondary particle size was 160 nm and D99 was 0.5 μm.
In order to examine the coarse particle content, the amount of coarse particles of 3 μm or more was determined from the mass increase before and after filtration with a laser filter in the same manner as in Example 1. As a result, the amount of coarse particles of 3 μm or more was 20 ppm in the solid.
Further, the above-mentioned polishing agent for planarizing the semiconductor was diluted 5 times with deionized water, and was polished by the same polishing test method as in Example 1. The polishing rate was 350 nm / min. When the wafer surface was observed with an optical microscope, ten scratches were observed on the entire surface of the 200 mm wafer.

(Comparative Example 1)
Cerium carbonate: 6 kg was put in an alumina container and baked in air at 800 ° C. for 2 hours to obtain 3 kg of yellowish white powder. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide.

  In the same manner as in Example 1, 1000 g of the prepared cerium oxide, polyacrylic acid ammonium salt aqueous solution (40% by mass): 80 g, and deionized water: 5600 g were mixed and stirred for 10 minutes, and then bead mill (Ashizawa) -Wet pulverization was performed for 30 minutes using a fine tech. The resulting dispersion was allowed to settle at room temperature (25 ° C.) for 20 hours, and the supernatant was collected. The supernatant is filtered through a mass production filter having a pore size of 1.0 μm, and then filtered again through a mass production filter having a pore size of 1.0 μm, and deionized water is added to adjust the solid content concentration to 5% by mass. A flattening abrasive was prepared.

The particle size of the obtained abrasive was measured in the same manner as in Example 1. As a result, the median value (D50) of the secondary particle size was 190 nm, and D99 was 0.7 μm.
In order to examine the content of coarse particles, the amount of coarse particles of 3 μm or more was determined from the mass increase before and after filtration with a laser filter in the same manner as in Example 1 for the obtained semiconductor planarization abrasive. As a result, the amount of coarse particles of 3 μm or more was 500 ppm in the solid.
Further, the above-mentioned polishing agent for planarizing the semiconductor was diluted 5 times with deionized water, and was polished by the same polishing test method as in Example 1. When the polishing speed was 650 nm / min and the wafer surface was observed with an optical microscope, 50 scratches were observed on the entire surface of the 200 mm wafer.

(Comparative Example 2)
6 kg of cerium carbonate was placed in an alumina container and baked in air at 800 ° C. for 2 hours to obtain 3 kg of yellowish white powder. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide.

  In the same manner as in Example 2, 1000 g of the cerium oxide prepared above, 80 g of ammonium polyacrylate aqueous solution (40% by mass): 80 g, and deionized water: 5600 g were mixed and stirred for 10 minutes, and then bead mill (Ashizawa) -Wet pulverization was performed for 30 minutes using a fine tech. The obtained dispersion was allowed to settle at room temperature (25 ° C.) for 100 hours, and the supernatant was collected. The supernatant is filtered through a mass production filter having a pore size of 0.7 μm, and then filtered again through a mass production filter having a pore size of 0.7 μm, and deionized water is added to adjust the solid content concentration to 5% by mass. A flattening abrasive was prepared.

The particle size of the obtained abrasive was measured in the same manner as in Example 1. As a result, the median value (D50) of the secondary particle size was 160 nm and D99 was 0.5 μm.
In order to examine the content of coarse particles, the amount of coarse particles of 3 μm or more was determined from the mass increase before and after filtration with a laser filter in the same manner as in Example 1 for the obtained semiconductor planarization abrasive. As a result, the amount of coarse particles of 3 μm or more was 50 ppm in the solid.
Further, the above abrasive was diluted 5 times with deionized water and polished by the same polishing test method as in Example 1. When the wafer surface was observed with an optical microscope at a polishing rate of 350 nm / min, 15 scratches were observed on the entire surface of the 200 mm wafer.

(Comparative Example 3)
6 kg of cerium carbonate was placed in an alumina container and baked in air at 800 ° C. for 2 hours to obtain 3 kg of yellowish white powder. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide.

  The produced cerium oxide: 1000 g, ammonium polyacrylate aqueous solution (40% by mass): 80 g, and 5600 g of deionized water were mixed and stirred for 10 minutes, and then with a bead mill (manufactured by Ashizawa Finetech Co., Ltd.). Wet grinding was performed for 2 hours. In the same manner as in Example 2, the obtained dispersion was allowed to settle at room temperature (25 ° C.) for 100 hours, and the supernatant was collected. The supernatant is filtered through a mass production filter having a pore size of 0.7 μm, and then filtered again through a mass production filter having a pore size of 0.7 μm, and deionized water is added to adjust the solid content concentration to 5% by mass. A flattening abrasive was prepared.

The particle size of the obtained abrasive was measured in the same manner as in Example 1. As a result, the median value (D50) of the secondary particle size was 160 nm and D99 was 0.5 μm.
In order to examine the coarse particle content, the amount of coarse particles of 3 μm or more was determined from the increase in mass before and after filtration with a laser filter in the same manner as in Example 1. As a result, the amount of coarse particles of 3 μm or more was 30 ppm in the solid.
Further, the above-mentioned polishing agent for planarizing the semiconductor was diluted 5 times with deionized water, and was polished by the same polishing test method as in Example 1. When the polishing speed was 350 nm / min and the wafer surface was observed with an optical microscope, 30 scratches were observed on the entire surface of the 200 mm wafer.

  The results of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1 below.

As described in Examples and Comparative Examples, by mixing malonic acid with cerium carbonate and firing, the grindability of cerium oxide is improved, and compared with the case where malonic acid is not mixed, the large particle size particles in the abrasive The content of can be kept low, and the generation of scratches can be reduced. When Example 1 and Comparative Example 1 are compared with Example 2 and Comparative Example 2, the values of D50 and D99 are the same, but those of Examples are more easily pulverized and have a large particle size of 3 μm or more. This is due to the difference in the content of (the content of Examples is small).
In addition, when malonic acid is not mixed, it takes a long time to pulverize in order to reduce the content of large-sized particles, increasing the possibility of contamination with wear powder, and at the same time involved in pulverizing for a long time. First, the reduction in the content of the large particle size is not as great as when malonic acid is mixed, and the effect of reducing scratches is inferior.
In Comparative Example 2 and Comparative Example 3, the pulverization time in Comparative Example 2 was set to 30 minutes, whereas the pulverization time in Comparative Example 3 was set to 2 hours. Example 3 is more common. This is presumably because the parts of the pulverizer were worn and the abrasion powder was mixed in the abrasive.

Claims (7)

  Cerium oxide particles obtained by pulverizing cerium oxide obtained by firing a mixture of cerium carbonate and malonic acid, and water, and the median secondary particle diameter of the cerium oxide is 0.1 to 1 μm. Cerium oxide abrasive.   The cerium oxide abrasive according to claim 1, wherein the mixing ratio of malonic acid is 0.5 to 6 mol with respect to 1 mol of cerium carbonate.   The cerium oxide abrasive according to claim 1 or 2, wherein the content of cerium oxide particles having a secondary particle size of 3 µm or more is 500 ppm or less in the entire cerium oxide.   4. The cerium oxide abrasive according to claim 1, further comprising a dispersant.   5. The cerium oxide abrasive according to claim 1, wherein 99% by volume of the entire cerium oxide secondary particles have a particle size of 1 μm or less.   Using the cerium oxide abrasive according to any one of claims 1 to 5, while supplying a polishing liquid between a substrate having a film to be polished and a polishing cloth, the substrate is pressed against the polishing cloth and pressurized, A substrate polishing method for polishing a substrate having a film to be polished by relatively moving the film to be polished and a polishing cloth.   7. The method for polishing a substrate according to claim 6, wherein the predetermined substrate is a semiconductor chip on which at least a silicon oxide film is formed.