JP2001115144A - Polishing material, method for polishing substrate, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polishing material that can polish the surface of a substrate such as a silica film without leaving scratches thereon. SOLUTION: Provided are a polishing material prepared by dispersing hollow microparticles or microparticles containing a liquid phase within them in a medium, a method for polishing therewith, and a semiconductor device using a substrate polished therewith. It is preferable that the microparticles have a median particle diameter of 1-500 nm. The microparticles are exemplified by ones made of a substance represented by the formula: SiOx (wherein (x) is 0.9-2.20) and having a bulk density equal to 10-90% of the true density. The medium is exemplified by water optionally containing a dispersant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an abrasive, a method for polishing a substrate, and a semiconductor device.

[0002]

2. Description of the Related Art At present, high-density and high-definition semiconductor devices are being developed, and design rules are on the order of sub-half microns. As a technique that has been developed in response to such demands for strict miniaturization, there is CMP (chemical mechanical polishing). According to this technique, in a manufacturing process of a semiconductor device, a layer to be exposed is completely flattened, the burden of the exposure technique is reduced, and the yield can be stabilized. For example, it is a technique that is indispensable when planarizing an interlayer insulating film, planarizing a buried insulating film at the time of trench isolation, and planarizing a copper wiring or the like. This technique is disclosed, for example, in US Pat. No. 4,944,836.

[0003] In a generation of a device having a design rule of 0.5 μm or more in element isolation forming technology in an integrated circuit, LOCO is required.
S (Silicon Local Oxidation) has been used, but with further miniaturization of processing dimensions, a shallow trench isolation technique with a small element isolation width is being adopted. In shallow trench isolation, CMP is an indispensable technique for removing an excess silicon oxide film embedded on a substrate.

In the metal wiring forming technology, in the generation of the design rule of 0.25 μm or less, W or the like is used for the Al wiring and the plug on the insulating film. Cu or C to satisfy electrical characteristics
uAl alloys are being adopted. Embedded wiring technologies such as damascene and dual damascene are being studied as wiring technologies for Cu and CuAl alloys, and CMP is indispensable in order to remove excess metal embedded on the substrate. The damascene method is disclosed in, for example, JP-A-2-278822. 2. Description of the Related Art Conventionally, in a semiconductor device manufacturing process, an insulating film such as silicon oxide formed by a method such as plasma CVD, low pressure-CVD, sputtering, or electroplating, a capacitor ferroelectric film, and planarization of wiring metal or metal alloy. In addition, fumed silica, colloidal silica, alumina-based abrasives, and the like are used as a CMP abrasive for forming a buried layer. As design rules have shrunk, semiconductor chip defects due to polishing scratches introduced into interlayer insulating films, insulating films for isolating shallow trenches, metal buried layers, and the like have come to the fore. The polishing scratches cause a short circuit in the wiring, leading to a decrease in the yield of the semiconductor chip. Abrasive grain properties that cause scratches include hardness and size of the abrasive grains. Alumina-based and fumed silica-based abrasive grains have high hardness, and polishing flaws are easily introduced into a metal wiring buried layer and the like. Colloidal silica has a relatively low hardness and scars are less likely to be introduced than other abrasive grains.
Since sodium silicate is used as a raw material, there is a problem of impurities such as Na in abrasive grains.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a CMP technique for forming a shallow trench isolation, forming a metal buried wiring, and the like, which eliminates polishing scratches on a silicon oxide film, a metal buried film, and the like, and has a low impurity contamination. And a polishing method for a substrate, and a semiconductor device using the substrate.

[0006]

SUMMARY OF THE INVENTION The present invention provides an abrasive in which hollow fine particles or fine particles containing a liquid phase are dispersed in a medium, a method for polishing a substrate using the same, and a substrate polished with the abrasive. The present invention relates to a semiconductor device used.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as a method for preparing fine particles, micelles are formed by a surfactant, the vicinity of the interface is used as a reaction field, and the reaction product reacts to form an inorganic oxide on the micelle surface. The fine particles are taken out and dried to obtain hollow fine particles. If the drying is not performed, the fine particles contain a liquid phase inside. If the particle size is large, polishing scratches are likely to occur, and if it is too small, the polishing rate is extremely low. Therefore, the median value of the particle size is preferably in the range of 1 to 500 nm. Although the composition of the fine particles is not particularly limited, silica is composed of silicon and oxygen, and _{x in} the chemical formula SiO x is 0.90 or more.
It is preferably 20 or less. If the bulk density is too low, the outer shell is thin and easily cracked. Conversely, if the bulk density is high, it cannot be distinguished from solid particles, so that the bulk density is 10% or more of the true density.
0% or less is preferable. Since metallic impurities such as Na and K in the abrasive deteriorate the characteristics of the semiconductor, the content is preferably 1 ppm or less.

As the medium, water is preferably used from the viewpoints of safety, ease of waste liquid treatment, good polishing characteristics, and the like. Abrasives can contain additives, and ammonia, acetic acid, nitric acid, water-soluble organic polymers, water-soluble anionic surfactants, water-soluble nonionic surfactants in terms of dispersion stability of abrasive grains as additives It is preferably at least one selected from agents and water-soluble amines. The concentration of the abrasive grains is preferably from 0.5 to 15% by weight from the viewpoint of the polishing rate. The concentration of the additive is preferably 0.001 to 10% by weight from the viewpoint of dispersibility.

[0009] The hollow fine particles in the present invention are preferably produced as follows. Dissolve the surfactant in the solvent. The solvent is not limited to one type, and the concentration of the surfactant is in a range where spherical micelles are formed. The range varies depending on the type of the surfactant and the solvent, but is generally 0.00
It is about 01 to 1 mol / l. The temperature at this time is not particularly limited, but is usually room temperature. The dissolution method is also not particularly limited, but usually by a stirring rod. Next, the raw material of the inorganic oxide is mixed with the surfactant solution. The temperature and the mixing method at this time are not particularly limited. It is usually performed at room temperature with a stir bar. The concentration of the raw material of the inorganic oxide is not particularly limited, but an extremely high concentration must be avoided in order to dissolve uniformly. This upper limit concentration varies depending on the type of the inorganic oxide raw material, the type of the surfactant solution, and the like. If the concentration is too low, the yield of the product will be poor. The catalyst is then added and mixed. The temperature and the method of mixing are not particularly limited, but usually the stirring is carried out at room temperature with a stirring bar. The type and concentration of the catalyst differ depending on the inorganic oxide raw material. Generally, aqueous ammonia, acetic acid, hydrochloric acid, nitric acid and the like are used, and the concentration is in a range of pH 1 to 11.

The abrasive may contain an oxidizing agent, a metal etching agent and an anticorrosive, and known oxidizing agents can be used. In particular, selected from hydrogen peroxide, ferric nitrate and cerium ammonium nitrate. Preferably, at least one of them is used. As the metal etching agent, known agents can be used, but it is particularly preferable that the metal etching agent is at least one selected from organic acids, bromine, aqueous hydrogen fluoride and aqueous ammonium. Known anticorrosives can be used, but benzotriazole and its derivatives are particularly preferred when the metal is copper.

The above-mentioned abrasive is used for polishing a metal film, a silica film and the like formed on a substrate. Polishing load is 100
１０００1000 g / cm ² is preferred. The abrasive of the present invention,
It contains hollow fine particles or fine particles containing a liquid inside. The surface of the shallow trench isolation / buried insulating film or metal buried layer is easily damaged when the abrasive grains have a large particle diameter and high hardness. Also, even if the particle size is small,
Hard materials such as diamonds are easily scratched. The polishing rate is larger as the grain size is larger and the hardness is higher as the hardness is higher. In order to obtain particles having a high polishing rate and hardly causing polishing scratches, it is necessary to adjust the particle size and hardness. The mechanical strength of particles represented by hardness is governed by the porosity of the particles. The higher the porosity, that is, the lower the bulk density, the lower the mechanical strength. As the particles for reducing the bulk density, there are hollow fine particles or fine particles containing a liquid phase inside. When the particle size is large, polishing scratches are likely to occur, so the particle size of the fine particles is preferably 1 to 500 nm. Further, since it is used for polishing a semiconductor chip, the content of an alkali metal which deteriorates its characteristics is preferably suppressed to 1 ppm or less.

The abrasive of the present invention is of high purity, and contains Na,
K, Si, Mg, Ca, Zr, Ti, Ni, Cr, Fe
Is preferably 1 ppm or less. The particle size of the fine particles can be controlled by the size of the micelle, that is, the type of the surfactant, the amount of the liquid phase incorporated into the surfactant, and the like. Surfactants include anionic surfactants,
Cationic, non-ionic and amphoteric surfactants can be used. Examples of the anionic surfactant include carboxylic acid type (aliphatic monocarboxylate such as sodium laurate, N-acyloylglutamate such as sodium lauroylglutamate), and sulfonic acid type (alkylbenzene such as sodium dodecylbenzenesulfonate). Sulfonate, naphthalene sulfonate formaldehyde condensate, dialkyl sulfosuccinate such as di-2-ethylhexyl sodium sulfosuccinate, etc., sulfate ester type (alkyl sulfate such as sodium dodecyl sulfate), phosphate ester type ( Alkyl sulfate polyoxyethylene salts such as dodecyl polyoxyethylene hydrochloride, and alkyl phosphate salts such as sodium monolauryl phosphate).

Examples of the cationic surfactant include amine salt type (alkylamine salt such as stearylamine hydrochloride), quaternary ammonium salt type (alkyltrimethylammonium salt such as stearyltrimethylammonium chloride, distearyldimethylammonium chloride). And the like, and alkyldimethylbenzylammonium salts such as lauryldimethylbenzylammonium chloride).

Examples of the non-ionic surfactant include ester type (glycerin fatty acid ester such as glycerin monostearate, sorbitan fatty acid ester such as sorbitan monostearate, sucrose fatty acid ester such as sucrose stearate), and the like. Ether type (polyoxyethylene alkylphenyl ether such as polyoxyethylene nonyl phenyl ether, polyoxyethylene alkyl ether such as dodecyl polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, etc.), ester ether type (polyethylene glycol oleic acid) Polyoxyethylene sorbitan fats such as polyethylene glycol fatty acid esters such as esters and polyoxyethylene sorbitan monopalmitate Ester, etc.), and the like alkanolamides type (such as fatty acid alkanolamides, such as lauric acid diethanolamide).

Examples of the amphoteric surfactant include carboxy betaine type (N, N-dimethyl-N-alkylamino betaine such as lauryl dimethyl acetate betaine) and glycine type (2-undecyl-N-carboxymethyl-N-type).
2-alkyl-1-hydroxyethyl-1-carboxymethylimidazolinium betaine such as hydroxyethyl imidazolinium betaine). As a raw material of the inorganic oxide, metal organic compounds such as metal alkoxide, metal acetylacetonate, and metal carboxylate, and metal inorganic compounds such as nitrate, chloride, and oxychloride can be used.

Known acid catalysts include organic acids such as acetic acid, malic acid and succinic acid, and mineral acids such as hydrochloric acid and nitric acid.
Known base catalysts such as ammonia and choline can be used as the base catalyst. Solvents such as water, alcohols (methanol, ethanol, propanol, etc.), methane-based hydrocarbons (hexane, heptane, octane, etc.), aromatic hydrocarbons (benzene, toluene, xylene, etc.) alone or in combination of two or more Can be used.

When the fine particles in the present invention are used as an abrasive, the medium is preferably water. When dispersing in water, as a dispersant, ammonia, acetic acid, nitric acid, acrylic acid polymer, water-soluble organic polymers such as polyvinyl alcohol,
Water-soluble anionic surfactants such as ammonium lauryl sulfate and polyoxyethylene lauryl ether ammonium sulfate; water-soluble nonionic surfactants such as polyoxyethylene lauryl ether and polyethylene glycol monostearate; and monoethanolamines. .

As a method for dispersing these fine particles in water, a homogenizer, an ultrasonic disperser, a ball mill, or the like can be used in addition to the usual dispersion treatment using a stirrer. There is no particular limitation on the particle concentration of the abrasive, and it is usually 0.1%.
It is about 5 to 15% by weight. The concentration of the polymer dispersant is from 0.001 to 10% by weight based on the particles.

The abrasive containing fine particles of the present invention can be used as it is as an abrasive for a substrate on which a metal film, a silica film, a silicon nitride film or the like is formed. An oxidizing agent, a metal etching agent, an anticorrosive, or the like can be added to the abrasive of the substrate on which the metal film is formed, and used. Examples of the oxidizing agent include known materials such as hydrogen peroxide, nitric acid, and ozone water, and hydrogen peroxide is preferable. Known organic acids such as formic acid, acetic acid and citric acid can be mentioned as metal etching agents, and known ones such as ammonia and benzotriazole as anticorrosives.

In the present invention, the particle size of the fine particles is measured by observation with a scanning electron microscope (for example, Model S-900 manufactured by Hitachi, Ltd.). The particle size was defined as the square root of the product of the major axis and the minor axis of the particle. The volume of the sphere obtained from the particle size determined in this way was defined as the volume of the particle. Also,
The median value is the median value of the volume particle size distribution, and means the particle size when the volume ratio of the particles is integrated from the finer particle size and reaches 50%. That is, when particles having a volume ratio of V1% are present in the range of the particle diameter of a certain section Δ, and the average particle diameter of the section Δ is di, the particles of the particle diameter di accumulate V1 (vol%). , Vi = 50%, and let di be the median value.

The silicon oxide film layer or the silicon nitride film layer formed on the semiconductor substrate is eliminated by the polishing method using the polishing material of the present invention to eliminate irregularities on the surface of the silicon oxide film layer or the silicon nitride film layer. Make the surface smooth over the entire surface. In addition, in order to use it for shallow trench isolation, it is necessary that the generation of scratches during polishing is small. Here, as a polishing apparatus, a general polishing apparatus having a holder for holding a semiconductor substrate and a platen on which a polishing cloth (pad) is attached (a motor or the like capable of changing the number of rotations is attached) is used. it can. As the polishing cloth, general nonwoven fabric, foamed polyurethane, porous fluororesin and the like can be used, and there is no particular limitation. Further, it is preferable to perform a groove process on the polishing cloth so that the polishing material is accumulated. The polishing conditions are not limited, but the rotation speed of the platen is preferably low rotation of 100 rpm or less so that the semiconductor does not jump out. The pressing pressure of the semiconductor substrate having the film to be polished against the polishing cloth is preferably 100 to 1000 gf / cm ² , and in order to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern, 200 to 500 gf / cm ^2.
gf / cm ² is preferred. While polishing,
An abrasive is continuously supplied to the polishing cloth by a pump or the like. Although the supply amount is not limited, it is preferable that the surface of the polishing cloth is always covered with the abrasive.

After the polishing, the semiconductor substrate is preferably washed well in running water, and then dried using a spin drier or the like to remove water droplets adhering to the semiconductor substrate. After forming the shallow trench isolation on the Si substrate in this manner, a silicon oxide insulating film or a silicon nitride insulating film layer and an aluminum wiring thereon are formed, and the silicon oxide film or the silicon nitride film formed thereon is removed. Flatten. A second aluminum wiring layer is formed on the planarized silicon oxide film or silicon nitride film layer, and a silicon oxide or silicon nitride film is formed again between the wirings and on the wirings by the above-described method. According to the invention, unevenness on the surface of the insulating film is eliminated, and a smooth surface is formed over the entire surface of the semiconductor substrate. By repeating this process a predetermined number of times, a semiconductor having a desired number of layers is manufactured.

After forming a shallow trench isolation on the Si substrate, a trench for an embedded wiring is formed on the interlayer insulating film layer and the surface thereof, and a barrier metal layer such as TiN or TaN and a seed layer for the wiring metal are formed by sputtering. Is formed, and a Cu or CuAl alloy is deposited by an electrolytic plating method or the like. By applying the abrasive of the present invention to this film formation layer, metal can be embedded only in the wiring groove. By repeating this process a predetermined number of times, a desired number of semiconductor layers is manufactured.

An embodiment of the present invention will be described. Example 1 (1) Production of Hollow Fine Particles 1514 g of heptane, 398 g of pure water, 486 g of ammonium di-2-ethylhexylsuccinate, 2.5 g of acetic acid and 1500 g of tetraethoxysilane were mixed and stirred.
It was left at ℃ for 1 week. After the oil component is separated by distillation, 150
After drying at ℃ for 1 hour, heat treatment was carried out at 500 ℃ to obtain silica hollow fine particles. Observation of the obtained hollow fine particles with a scanning electron microscope (S-900, manufactured by Hitachi, Ltd.) revealed that the median particle size was 100 nm. The bulk density was measured and found to be 1.5 g / cc.

(2) Preparation of Abrasive Material 150 g of the hollow fine particles obtained in the above (1), 2 g of polyacrylic acid, 800 g of deionized water and 48 g of ammonia water were stirred and mixed to obtain an abrasive having a particle concentration of 15% by weight. . (3) Polishing of insulating film layer
An Si wafer having an SiO ₂ insulating film formed by an EOS-plasma CVD method was set thereon, and a holder was placed with the insulating film face down on a surface plate on which a polishing pad made of a porous urethane resin was attached. Processing load is 300g / cm ²
We put weight so that it becomes. Put 3 abrasives on the surface plate
While dropping at a speed of 5 cc / min, the platen is rotated at 30 rpm.
m for 2 minutes to polish the insulating film. After polishing, the wafer was removed from the holder, washed well with running water, and further washed with an ultrasonic cleaner for 20 minutes. After the cleaning, water droplets were removed from the wafer with a spin dryer, and the wafer was dried with a dryer at 120 ° C. for 10 minutes. Optical interference type film thickness measuring device (NanoSpec / AFT5100 manufactured by Nanometrics)
As a result of measuring the change in film thickness before and after polishing using a mold, the polishing resulted in 200 nm (polishing rate: 100 nm / mi).
n. It was confirmed that the insulating film was abraded to have a uniform thickness over the entire surface of the wafer. In addition, when the surface of the insulating film was observed using an optical microscope (UFX-IIA manufactured by Nikon Corporation), no clear scratch was found.

Example 2 (1) Preparation of Hollow Fine Particles 1,050 g of tetraethoxysilane, 1800 g of a 0.1 M hydrochloric acid aqueous solution, 460 g of ethanol, and 250 g of dodecyltrimethylammonium bromide were mixed, stirred and left at room temperature for 10 days. Next, it was dried at 100 ° C. for 24 hours, and further heat-treated at 500 ° C. for 5 hours to obtain hollow silica fine particles.
Observation of the obtained hollow fine particles with a scanning electron microscope in the same manner as in Example 1 showed that the particles were spherical and had a median particle size of 70 n.
m. When the bulk density was measured, it was 1.7.
g / cc. (2) Preparation of Polishing Material and Polishing of Insulating Film When a polishing material was prepared and the insulating film was polished in the same manner as in Example 1, and the polished surface was observed with an optical microscope in the same manner, no clear scratch was found. Was. When the change in film thickness before and after polishing was measured in the same manner as in Example 1, the polishing rate was 110 nm.
/ Min.

Example 3 (1) Preparation of hollow fine particles containing a liquid phase inside 500 g of tetraethoxysilane, 2500 g of dodecyltrimethylammonium, 13000 g of water, 20 M of 1M hydrochloric acid
g was mixed, stirred and left at room temperature for 5 days. Observation of the resulting fine particles containing a liquid phase therein using a scanning electron microscope revealed that the particles were spherical and had a median particle size of 50 nm. The bulk density was 1.8 g / cc. (2) Preparation of Abrasive Material and Polishing of Insulating Film The obtained hollow microparticles were used as an abrasive material in the same manner as in Example 1 without drying or other treatment, and the insulating film was polished and polished in the same manner as in Example 1. When the change in the film thickness before and after the measurement was measured, the polishing rate was 100 nm / min. Similarly, when observed with an optical microscope, no clear damage was found.

[0028]

According to the present invention, there is provided an abrasive which can polish a surface to be polished such as a silica film without being damaged.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kenzo Susa 48 Wadai, Tsukuba-shi, Ibaraki F-term in Hitachi Chemical Co., Ltd. F-term (reference)

Claims (13)

[Claims] An abrasive in which hollow fine particles are dispersed in a medium. 2. An abrasive in which fine particles containing a liquid phase are dispersed in a medium. 3. The median particle diameter of the fine particles is 1 to 500 nm.
The abrasive according to claim 1 or 2, wherein 4. The abrasive according to claim 1, wherein the fine particles are an inorganic oxide. 5. The x value of the chemical formula SiO _x of the fine particles is 0.9.
The abrasive according to claim 1, wherein the abrasive is 0 or more and 2.20 or less. 6. The abrasive according to claim 1, wherein the bulk density of the fine particles is 10% or more and 90% or less of the true density. 7. The abrasive according to claim 1, wherein the fine particles have a metal impurity of 1 ppm or less. 8. The abrasive according to claim 1, wherein the medium is water. 9. The abrasive according to claim 1, wherein the abrasive contains a dispersant. 10. A dispersant comprising ammonia, acetic acid, nitric acid,
The abrasive according to claim 9, wherein the abrasive is at least one selected from a water-soluble organic polymer, a water-soluble anionic surfactant, a water-soluble nonionic surfactant, and a water-soluble amine. 11. A substrate polishing method for polishing a predetermined substrate using the abrasive according to claim 1. 12. The method according to claim 11, wherein the substrate is a semiconductor chip on which a silica film is formed. 13. A semiconductor device using a substrate polished using the polishing material according to claim 1.