JP2007154155A - Method for producing metallic oxide microparticle for abrasive, abrasive, and method for grinding substrate and method for producing semiconductor device by using the abrasive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing metallic oxide microparticles for abrasive, capable of performing CMP in a short time without causing grinding defects on a silicon oxide membrane, a metal embedded membrane and the like in CMP technologies such as interlayer insulating film planarization, shallow trench separation forming and metal embedding wiring forming, to provide an abrasive containing the metallic oxide microparticles produced by the method, and to provide a method for grinding substrates and a method for producing the semiconductor devices by using the abrasive. <P>SOLUTION: The method for producing the metallic oxide microparticles for an abrasive is characterized by finely forming droplets from a solution containing a metallic compound and an organic material and heat treating the droplets. The abrasive comprises the metallic oxide microparticles for an abrasive, produced by the method. The method for grinding the substrates and the method for producing the semiconductor devices by using the abrasive are provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing metal oxide fine particles for abrasives, an abrasive comprising metal oxide fine particles produced by the method, a method for polishing a substrate using the same, and a method for producing a semiconductor device.

  At present, the density and high definition of semiconductor elements are increasing, and the design rule is around 0.1 μm. There is CMP (chemical mechanical polishing) as a technology that has been developed in order to satisfy such a demand for strict miniaturization.

  This technology can completely planarize the layer to be exposed in the manufacturing process of the semiconductor device, reduce the burden of the exposure technology, and stabilize the yield. For example, during the planarization of the interlayer insulating film and the trench isolation This technique is indispensable for the planarization of the buried insulating film and the planarization of the copper wiring, and is disclosed in, for example, Patent Document 1.

  LOCOS (Silicon Local Oxidation) has been used in the generation of design rules of 0.51 μm or more in the element isolation formation technology in integrated circuits, but shallow trench isolation technology with a small element isolation width as the processing dimensions become smaller. Is adopted. In shallow trench isolation, CMP is an essential technique for removing an excess silicon oxide film embedded on a substrate.

  Also in the metal wiring formation technology, Cu and CuAl alloys are being adopted in order to satisfy the required electrical characteristics as processing dimensions become finer. Embedded wiring techniques such as damascene and dual damascene have been studied as wiring techniques for Cu and CuAl alloys, and CMP is indispensable for removing excess metal embedded on the substrate. The damascene method is disclosed in Patent Document 2, for example.

  Conventionally, in a semiconductor device manufacturing process, an insulating film such as silicon oxide, a capacitor ferroelectric film, and a wiring metal formed by a method such as plasma-CVD (chemical vapor deposition), low-pressure CVD, sputtering, or electroplating. Abrasives containing abrasive particles such as fumed silica, colloidal silica, and alumina as CMP abrasives for flattening metal or metal alloys, or CMP abrasives for forming metal buried layers is doing.

With the reduction of design rules, semiconductor chip defects due to polishing flaws introduced into interlayer insulating films, insulating films for shallow trench isolation, and metal buried layers have been highlighted. Polishing scratches are a problem because they cause wiring shorts and lead to a decrease in the yield of semiconductor chips.
U.S. Pat. No. 4,944,836 Japanese Patent Laid-Open No. 02-278822

  In the present invention, CMP processing such as planarization of an interlayer insulating film, flattening of an insulating film for shallow trench isolation, formation of a metal buried wiring, etc. can be performed in a short time without causing polishing scratches on the insulating film, the metal buried layer, etc. A method for producing metal oxide fine particles for abrasives, an abrasive comprising metal oxide fine particles for abrasives produced by the method, a method for polishing a substrate using the abrasive, and a method for producing a semiconductor device It is to provide.

  In general, when an insulating film or a metal-embedded layer is subjected to CMP treatment, if the abrasive grains in the abrasive are large, polishing flaws are likely to occur. Conversely, if the particles are small, the occurrence of polishing flaws is reduced. The speed will be slow. The inventors focused on properties such as crystallite size and crystal strain of the abrasive grains in the abrasive, examined the influence of these on the generation of polishing flaws and the polishing rate, and the crystallite size was large and crystal strain was reduced. We considered that small spherical particles could suppress the generation of polishing flaws and could be polished in a short time, and intensively studied methods for producing such particles.

  The present invention relates to (1) a method for producing metal oxide fine particles for abrasives, characterized in that a solution containing a metal compound and an organic substance is finely divided and heat-treated.

  In the present invention, (2) the metal compound is a metal nitrate, ammonium nitrate, sulfate, ammonium sulfate, carbonate, acetate, oxalate, chloride, acetylacetonate salt, alkoxide, hydroxide In addition, the present invention relates to the method for producing metal oxide fine particles for abrasives according to (1) above, which is at least one selected from oxides.

  In the present invention, (3) the metal oxide is selected from one or more metal compounds selected from cerium oxide, zirconium oxide, titanium oxide, silicon oxide, and aluminum oxide, or cerium, zirconium, titanium, silicon, and aluminum. It is related with the manufacturing method of the metal oxide microparticles | fine-particles for abrasive | polishing materials as described in said (1) characterized by being the composite metal oxide of 2 or more types of metals.

  The present invention also relates to (4) the method for producing metal oxide fine particles for abrasives according to (1), wherein the organic substance is alcohol or an organic polymer.

  Further, the present invention provides (5) the two-fluid nozzle method, the three-fluid nozzle method, the ultrasonic atomization method, the electrostatic atomization method, the heating atomization method, the glass filter method, or a combination thereof, and the metal compound and The present invention relates to the method for producing fine metal oxide particles for abrasives according to (1) above, wherein a solution containing an organic substance is finely formed into droplets.

  Further, in the present invention, (6) the polishing according to (1), wherein the heat treatment of the droplet is performed in one or more kinds of reaction furnaces selected from an electric furnace, a flame furnace, and a plasma furnace. The present invention relates to a method for producing metal oxide fine particles.

  The present invention also includes (7) metal oxide fine particles for abrasives produced by the method for producing metal oxide fine particles for abrasives according to any one of (1) to (6). The present invention relates to an abrasive.

  The present invention also relates to (8) a method for polishing a substrate, wherein the substrate on which a film to be polished is formed is polished using the abrasive described in (7).

  The present invention also relates to (9) the method for polishing a substrate according to (8), wherein the film to be polished is an insulating film or a metal film.

  The present invention also relates to (10) the method for polishing a substrate according to (9), wherein the insulating film is a silicon oxide insulating film.

  In the present invention, (11) the metal film is any one or more of copper, aluminum, tungsten, tantalum, titanium, a metal compound thereof, and a metal alloy thereof (9) The present invention relates to a method for polishing a substrate.

  Furthermore, the present invention provides (12) a step of polishing a film to be polished using the abrasive described in (7) above, or a method for polishing a substrate according to any one of (8) to (11) above. A method of manufacturing a semiconductor device, comprising: polishing a semiconductor chip on which a silica film or a metal film is formed with the above-described polishing material.

  According to the manufacturing method of the present invention, it is possible to obtain metal oxide fine particles capable of achieving high-speed polishing without causing polishing scratches on a film to be polished such as an insulating film or a metal buried layer in a CMP process. Furthermore, according to the present invention, it is possible to manufacture a semiconductor device with a stable yield by polishing using an abrasive containing the resulting metal oxide fine particles.

  In the production method of the present invention, metal oxide fine particles for abrasives are produced by finely dropletizing a solution containing a metal compound and an organic substance and subjecting the liquid to heat treatment.

  Metal compounds used in the present invention are metal nitrates, ammonium nitrates, sulfates, ammonium sulfates, carbonates, acetates, oxalates, chlorides, acetylacetonate salts, alkoxides, hydroxides, oxides, etc. These may be hydrates. Among these, cerium compounds are preferable, cerium nitrate, ammonium nitrate, sulfate, ammonium sulfate, acetate, chloride, hydroxide, oxide, and hydrates thereof are more preferable, and ammonium nitrate of cerium is particularly preferable. preferable. Such a metal compound may be used alone or as a mixture of a plurality of types, and when the production method of the present invention is performed using the mixture, composite metal oxide fine particles of two or more types of metals are obtained.

  Examples of the organic substance used in the present invention include alcohols and organic polymers.

  Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, 2-methyl-2-propanol, 1-pentanol, 1-hexanol, 1- Examples include octanol, 1-decanol, cyclohexanol, 2-propen-1-ol, 1,4-butanediol, 1,2,3-propanetriol, and the like. These may be used alone or in combination of two or more.

  Examples of the organic polymer include polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyethyleneimine, polyvinylpyrrolidone, polydimethylacrylamide, polyethylene glycol, polyoxyethylene, and the like. These may be used alone or in combination of two or more.

  In the present invention, it is important to use an organic compound, whereby the crystallite size of the metal oxide fine particles obtained is increased, and the crystal strain is reduced.

  The solution containing a metal compound and an organic substance is obtained by dissolving or suspending a metal compound and an organic substance in a solvent. As the solvent, water, acetones, ketones, ethers, a mixed solvent thereof or the like is used, and water is particularly preferable.

  The solution may be prepared by dissolving or suspending the metal compound and the organic substance in a solvent, combining the metal compound and the organic substance dissolved or suspended in the solvent, or combining the metal compound and the organic substance. Either of them may be dissolved or suspended in a solvent, and the other may be added thereto.

  There are no particular limitations on the method for finely dropletizing a solution containing a metal compound and an organic substance. For example, a two-fluid nozzle method, a three-fluid nozzle method, an ultrasonic atomization method, an electrostatic atomization method, and a heating atomization method. , Glass filter method or a combination of these methods. Among these, the ultrasonic atomization method is used award. The average diameter of the finely droplets is preferably 50 μm or less, more preferably 20 μm or less, and particularly preferably 10 μm or less. When the average diameter of the droplets exceeds 50 μm, the resulting metal oxide fine particles may become large. The size of the droplet is adjusted by the droplet formation method, the concentration of the metal compound or organic substance in the solution, and the like.

  Next, the droplet is heated. The method for the heat treatment is not particularly limited, but is usually performed by introducing droplets into the reaction furnace and performing the heat treatment. The reaction furnace is not particularly limited as long as it is generally known, and for example, a tubular electric furnace, a flame furnace, a plasma furnace or the like can be used. The design form of the furnace may be either a vertical type or a horizontal type. In the case of the vertical type, the introduction of droplets may be performed from the upper side or the lower side.

  The introduction of droplets into the reactor is carried out by a method of spontaneous fall, a method of introduction with a carrier gas such as air, nitrogen, argon, hydrogen, oxygen, a method of vacuum suction, or a combination thereof, and the introduction speed. Is preferably constant. A gas containing oxygen may be introduced into the heating zone in order to convert the metal compound in the droplet into an oxide or to increase the crystallinity of the oxide.

  The heating temperature is not particularly limited and is appropriately selected, but is preferably 300 ° C. or higher, more preferably 400 ° C. or higher, and particularly preferably 500 ° C. or higher. When the heating temperature is less than 300 ° C., an incomplete metal oxide may be obtained, or a metal oxide having a small crystallite size or a metal oxide having a large crystal distortion may be obtained. An appropriate reactor is appropriately selected and used depending on the heating temperature to be set. There are no particular restrictions on the temperature distribution of the reactor. The heating time is also appropriately selected.

  As the metal oxide fine particles obtained as described above, two types selected from metal oxide fine particles such as cerium oxide, zirconium oxide, titanium oxide, silicon oxide, and aluminum oxide, or cerium, zirconium, titanium, silicon, aluminum, and the like. These are fine particles of a composite metal oxide of the above metals. The fine particles of the composite metal oxide can be obtained when a mixture of a plurality of types is used as the metal compound. When cerium oxide is used as the metal compound, crystal growth proceeds by heat treatment, and fine particles of cerium oxide having a large crystallite size and a small crystal distortion are obtained.

The metal oxide fine particles obtained by the production method of the present invention are useful as abrasive grains for abrasives, and have high crystallinity and high crystallinity with little crystal distortion. The crystallite size is 20 nm or more, and the crystal strain is 3% or less. The properties of the metal oxide fine particles can be determined by appropriately selecting various conditions such as the type of metal compound, the amount of metal compound, the type of organic material, the amount of organic material, the type of reaction furnace, the introduction rate, the heating temperature, and the heating time. You can control. The crystallite size and crystal strain are values calculated by the following formula.
The crystallite size was obtained by measuring powder X-ray diffraction, obtaining a symmetric profile parameter X by Rietveld analysis using Thompson, Cox, and Hastings pseudo-Forked functions as profile functions, and calculating from the following formula.

p = 180Kλ / πX
p: crystallite size (nm), K: Scherrer constant (0.9), λ: X-ray wavelength (nm), π: pi, X: Lorentz parameter (profile parameter)
Further, the crystal distortion was calculated from the following equation by measuring powder X-ray diffraction, obtaining a symmetrical profile parameter Y by Rietveld analysis using Thompson, Cox, and Hastings pseudo-Forked functions as profile functions.

S = (π / 180) Y × 100
S: Strain of crystal (%), π: Pi, Y: Lorentz parameter (symmetric profile parameter)
The abrasive of the present invention includes metal oxide fine particles produced by the method of the present invention. Such an abrasive is obtained by dispersing metal oxide fine particles in a slurry in a medium, and the metal oxide fine particles may be used alone or in combination. As the medium, water is preferably used. There is no limitation on the concentration of the metal oxide fine particles in the abrasive.

  When the metal oxide fine particles are dispersed in the medium, a dispersant can be used as necessary. The dispersant is not particularly limited as long as the metal oxide fine particles can be dispersed in the medium. For example, a (meth) acrylic acid polymer or an ammonium salt thereof; a water-soluble organic polymer such as polyvinyl alcohol or polyvinylpyrrolidone; Molecules; water-soluble anionic surfactants such as ammonium lauryl sulfate and ammonium polyoxyethylene lauryl ether; water-soluble nonionic surfactants such as polyoxyethylene lauryl ether and polyethylene glycol monostearate; and monoethanolamine; And water-soluble amines such as diethanolamine. The amount of the dispersant added is preferably in the range of 0.01 to 5 parts by weight with respect to 100 parts by weight of the metal oxide fine particles in view of the dispersibility of the metal oxide fine particles in the slurry and the anti-settling property. In order to increase the thickness, it is preferable to place the metal oxide fine particles in the disperser simultaneously or almost simultaneously with the dispersion treatment. As a method for dispersing the metal oxide fine particles in the medium, a homogenizer, an ultrasonic disperser, a bead mill, a ball mill, or the like can be used in addition to a dispersion treatment using a normal stirrer. Further, after the dispersion treatment, classification may be performed as necessary, and it can be carried out using a generally known natural sedimentation method, liquid cyclone method, centrifugal sedimentation method, wet high-pressure disperser or the like.

  In addition to the above-described components, the abrasive of the present invention generally contains additives such as colorants such as dyes and pigments, pH adjusters, and solvents other than water. You may add in the range which does not impair an effect.

The polishing method of the present invention is characterized in that a substrate on which a film to be polished is formed is polished using the polishing material of the present invention. The target film to be polished is an insulating film or a metal film, and these films may be a single layer or a stacked layer. Examples of the insulating film include a silicon oxide insulating film and a silicon nitride insulating film. For example, SiO ₂ formed by a CVD method using SiH ₄ or tetraethoxysilane (TEOS) as a Si source and oxygen or ozone as an oxygen source. A membrane is mentioned. Examples of the metal film include one or more kinds of metals such as copper, aluminum, tungsten, tantalum, and titanium, alloys of these metals, and compounds such as oxides and nitrides of these metals or metal alloys. The metal film is formed by a known method such as sputtering or plating. In the case of polishing a substrate on which a metal film is formed, an oxidizing agent, a metal etching agent, an anticorrosive agent or the like can be added to the polishing material. Examples of the oxidizing agent include hydrogen peroxide, nitric acid, ozone water and the like, and hydrogen peroxide is preferable. Examples of the metal etching agent include organic acids such as formic acid, acetic acid, and citric acid, and examples of the anticorrosion agent include ammonia and benzotriazole. As the substrate, a substrate related to semiconductor device manufacture, for example, a substrate in which an insulating layer is formed on a semiconductor substrate such as a semiconductor substrate in which a circuit element and a wiring pattern are formed, a semiconductor substrate in a stage in which a circuit element is formed, etc. Etc.

  Polishing of the film to be polished is performed by chemical mechanical polishing. Specifically, the substrate on which the film to be polished is formed is pressed against the polishing cloth and pressed, and the abrasive of the present invention is placed between the film to be polished and the polishing cloth. While being supplied to the substrate, the film to be polished is polished by relatively moving the film to be polished on the substrate and the polishing cloth.

  Hereinafter, the polishing method will be described by taking as an example the case of a semiconductor substrate on which an inorganic insulating film is formed as a film to be polished.

  In the polishing method of the present invention, as a polishing apparatus that can be used, a holder that holds a substrate having a film to be polished, a polishing cloth (pad) that can be pasted, and a motor that can change the number of rotations is attached. A general polishing apparatus having a surface plate can be used. For example, a polishing apparatus manufactured by Ebara Corporation: model number EPO111 can be used.

As the polishing cloth on the polishing surface plate, a general nonwoven fabric, foamed polyurethane, porous fluororesin and the like can be used, and there is no particular limitation. Further, it is preferable that the polishing cloth is grooved so that the abrasive is accumulated. The polishing conditions are not limited, but the rotation speed of the surface plate is preferably low rotation of 200 rpm or less so that the semiconductor substrate does not jump out, and the pressure (working load) applied to the semiconductor substrate is 1 kg / no. cm ² (98 kPa) or less is preferable. In order to satisfy the uniformity of the polishing speed within the surface to be polished and the flatness of the pattern, the pressure is more preferably 5 kPa to 50 kPa.

  In order to move the polishing cloth and the film to be polished relatively with the polishing film on the substrate pressed against the polishing cloth, specifically, at least one of the substrate and the polishing surface plate may be moved. In addition to rotating the polishing surface plate, polishing may be performed by rotating or swinging the holder. Further, a polishing method in which the polishing platen is rotated on a planetary surface, a polishing method in which a belt-like polishing cloth is moved linearly in one direction in the longitudinal direction, and the like can be given. The holder may be in any state of being fixed, rotating and swinging. These polishing methods can be appropriately selected depending on the surface to be polished and the polishing apparatus as long as the polishing cloth and the film to be polished are moved relatively.

During polishing, the slurry-like abrasive of the present invention is continuously supplied between the polishing cloth and the film to be polished by a pump or the like. The supply amount is not limited, but it is preferable that the surface of the polishing pad is always covered with an abrasive. Specifically, it is preferable that 0.005 to 0.40 ml is supplied per 1 cm ^{2 of} the polishing pad area.

  The semiconductor substrate after the polishing is preferably washed in running water, and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like. By polishing the inorganic insulating layer, which is the film to be polished, with the above-described abrasive, the surface irregularities can be eliminated and a smooth surface can be obtained over the entire surface of the semiconductor substrate.

  The abrasive and the polishing method of the present invention can be applied not only to the polishing of a silicon oxide film formed on a semiconductor substrate but also in the manufacturing process of various semiconductor devices. That is, the method for manufacturing a semiconductor device of the present invention includes a step of polishing a film to be polished using the polishing material of the present invention, or a step of polishing the film to be polished by the polishing method of the present invention. . As a film to be polished to which the present invention can be applied, for example, a silicon oxide film formed on a wiring board having a predetermined wiring, an inorganic insulating film such as glass or silicon nitride, polysilicon, Al, Cu, Ti, TiN, W, Ta , Films mainly containing TaN, etc., optical glass such as photomask / lens / prism, inorganic conductive film such as ITO, glass and crystalline material constituting optical integrated circuit / optical switching element / optical waveguide, end face of optical fiber, Examples include optical single crystals such as scintillators, solid laser single crystals, sapphire substrates for blue laser LEDs, and semiconductor single crystals such as SiC, GaP, and GaAs. Furthermore, the present invention can be applied to a polishing process for a magnetic disk glass substrate, a magnetic head, and the like.

  Hereinafter, the present invention will be described in detail by way of examples.

Example 1
An aqueous solution containing 1% by weight of cerium ammonium nitrate and 10% by weight of isopropyl alcohol was formed into droplets by using an ultrasonic vibrator equipped with a 2.4 MHz vibrator, and the liquid droplets were introduced into a tubular electric furnace. Heat treatment was performed at 0 ° C. to obtain fine particles. Phase identification of the fine particles by X diffraction method confirmed that it was cerium oxide. The obtained cerium oxide fine particles were subjected to powder X-ray diffraction precision measurement and subjected to Rietveld analysis. As a result, the crystallite size was 51 nm and the crystal strain was 0.71%.

Example 2
An aqueous solution containing 1% by weight of cerium ammonium nitrate and 5% by weight of polyacrylic acid was formed into droplets using an ultrasonic vibrator equipped with a 2.4 MHz vibrator, and the liquid droplets were introduced into a tubular electric furnace. Heat treatment was performed at 900 ° C. to obtain fine particles. Phase identification of the fine particles by X diffraction method confirmed that it was cerium oxide. The obtained cerium oxide fine particles were subjected to powder X-ray diffraction precision measurement and subjected to Rietveld analysis. As a result, the crystallite size was 55 nm and the crystal strain was 0.67%.

Comparative Example 1
A 1% by weight aqueous solution of cerium ammonium nitrate is formed into droplets using an ultrasonic vibrator equipped with a 2.4 MHz vibrator, and the liquid droplets are introduced into a tubular electric furnace and heated at 900 ° C. to form fine particles. Got. Phase identification of the fine particles by X diffraction method confirmed that it was cerium oxide. The obtained cerium oxide fine particles were subjected to powder X-ray diffraction precision measurement and subjected to Rietveld analysis. As a result, the crystallite size was 35 nm and the crystal strain was 1.20%.

Claims (12)

  A method for producing metal oxide fine particles for an abrasive, comprising: forming a solution containing a metal compound and an organic substance into fine droplets, and subjecting the droplets to heat treatment.   The metal compound is one or more selected from metal nitrate, ammonium nitrate, sulfate, ammonium sulfate, carbonate, acetate, oxalate, chloride, acetylacetonate, alkoxide, hydroxide, and oxide. The method for producing metal oxide fine particles for an abrasive according to claim 1.   The metal oxide is one or more metal oxides selected from cerium oxide, zirconium oxide, titanium oxide, silicon oxide, and aluminum oxide, or a composite of two or more metals selected from cerium, zirconium, titanium, silicon, and aluminum. 2. The method for producing fine metal oxide particles for abrasives according to claim 1, wherein the fine metal oxide particles are metal oxides.   The method for producing metal oxide fine particles for abrasives according to claim 1, wherein the organic substance is alcohol or an organic polymer.   The solution containing the metal compound and the organic substance is finely liquefied by a two-fluid nozzle method, a three-fluid nozzle method, an ultrasonic atomization method, an electrostatic atomization method, a heating atomization method, a glass filter method, or a combination thereof. 2. The method for producing metal oxide fine particles for abrasives according to claim 1, wherein the droplets are formed into droplets.   The method for producing metal oxide fine particles for abrasives according to claim 1, wherein the heat treatment of the droplets is performed in one or more types of reaction furnaces selected from an electric furnace, a flame furnace, and a plasma furnace.   An abrasive comprising metal oxide fine particles for abrasives produced by the method for producing metal oxide fine particles for abrasives according to any one of claims 1 to 6.   A method for polishing a substrate, comprising polishing a substrate on which a film to be polished is formed, using the abrasive according to claim 7.   9. The method for polishing a substrate according to claim 8, wherein the film to be polished is an insulating film or a metal film.   The method for polishing a substrate according to claim 9, wherein the insulating film is a silicon oxide insulating film.   10. The method for polishing a substrate according to claim 9, wherein the metal film is one or more of copper, aluminum, tungsten, tantalum, titanium, a metal compound thereof, and a metal alloy thereof.   A semiconductor device comprising a step of polishing a film to be polished using the abrasive according to claim 7 or a step of polishing by the substrate polishing method according to any one of claims 8 to 11. Manufacturing method.