JP5418571B2 - CMP polishing agent and substrate polishing method - Google Patents

Description

  The present invention relates to a CMP (Chemical Mechanical Polishing) polishing agent and a substrate polishing method used in a semiconductor element manufacturing process, for example, in a flattening process of an interlayer insulating film or a forming process of shallow trench isolation.

  Various microfabrication techniques have been researched and developed to increase the packaging density in the field of ultra-large scale integrated circuits, and the design rules are already in the order of sub-half microns. One of the techniques for satisfying such strict miniaturization requirements is a CMP polishing technique. Since this technique enables miniaturization by completely planarizing the layer to be exposed in the manufacturing process of a semiconductor device and improves the yield, for example, planarization of an interlayer insulating film or shallow trench This is a technique required when performing separation or the like.

  Conventionally, a LOCOS (silicon local oxidation) method has been used for element isolation in an integrated circuit, but in recent years, a shallow trench isolation method has been used to narrow the element isolation width. In the shallow trench isolation method, CMP is indispensable to remove the excess silicon oxide film formed on the wafer substrate, and a silicon nitride film is formed as a stopper under the silicon oxide film to stop polishing. It is common.

  As a CMP polishing agent for planarizing a silicon oxide insulating film or the like formed by a method such as plasma-CVD (Chemical Vapor Deposition) or low-pressure CVD in a semiconductor device manufacturing process, Alkaline silica-based abrasives having fumed silica as abrasive particles and a pH exceeding 9 have been widely used. On the other hand, abrasives using cerium oxide as abrasive particles, which have been widely used as glass surface abrasives for photomasks and lenses, have recently attracted attention as CMP abrasives. This technique is disclosed, for example, in JP-A-5-326469. Since cerium oxide-based abrasives are superior to silica-based abrasives in that the polishing rate of silicon oxide film is faster and polishing scratches are relatively few, various application studies have been made, and some of them have been put to practical use as semiconductor abrasives It has come to be. This technique is disclosed in, for example, Japanese Patent Laid-Open No. 9-270402.

  In recent years, as the number of semiconductor elements increases and the definition becomes higher, further improvement in yield and throughput of the semiconductor elements has been demanded. As a result, polishing scratch-free and higher-speed polishing has been desired for CMP processes using abrasives. Examples of a method for further reducing polishing flaws in a CMP process using a cerium oxide abrasive include a process improvement method such as a reduction in polishing pressure or platen rotation speed, and an abrasive improvement method such as a reduction in abrasive concentration or density. However, there is a problem that the polishing rate is lowered when either method is used.

JP-A-9-270402

  The present invention relating to a CMP abrasive provides an abrasive capable of improving particle removal performance in cleaning after polishing, having a high polishing rate and high flatness, and capable of reducing polishing scratches. The present invention relating to a substrate polishing method improves particle removal performance in cleaning after polishing, has a high polishing rate, high flatness, can reduce polishing scratches, and has excellent yield and workability. Is.

The present invention relates to a cerium oxide particle, a water-soluble polymer, a complexing agent with cerium, and a CMP abrasive containing water and having a complexing agent concentration with cerium of 0.1 wt% or more and 10.0 wt% or less.
In the present invention, the complex-forming agent is represented by the general formula (I).
Wherein R ¹ and R ² represent a substituted or unsubstituted alkyl group, and R ³ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms. The present invention relates to a CMP abrasive.
The present invention also relates to the aforementioned CMP abrasive wherein the complexing agent is acetylacetone.
The present invention also relates to any one of the aforementioned CMP abrasives, wherein the water-soluble polymer is at least one selected from the group consisting of a water-soluble anionic surfactant and a water-soluble nonionic surfactant.
The present invention also provides a semiconductor chip on which a silicon oxide insulating film is formed by supplying a CMP polishing agent containing cerium oxide particles, a water-soluble polymer, a complexing agent with cerium and water to a polishing pad on a polishing surface plate. The present invention relates to a method for polishing a substrate, wherein the substrate surface is polished through cerium oxide particles complexed on the surface by causing the surface to be polished and the polishing pad to move relative to each other and contacting the surface to be polished.
The complex formation between the β-diketone represented by the general formula (I) and the cerium particles is represented by the general formula (II).
(Wherein R ¹ , R ² and R ³ have the same meaning as in general formula (I)). When complexed on the surface of the cerium oxide particle in this way, the surface of the cerium particle is covered with a hydrophobic organic functional group. It is estimated that the effect of preventing adhesion of cerium oxide particles to the silicon oxide film surface is exhibited.

  The present invention relating to a CMP abrasive provides an abrasive capable of improving particle removal performance in cleaning after polishing, having a high polishing rate and high flatness, and capable of reducing polishing scratches. The present invention relating to a substrate polishing method improves particle removal performance in cleaning after polishing, has a high polishing rate, high flatness, can reduce polishing scratches, and has excellent yield and workability. Is.

It is explanatory drawing which shows uneven | corrugated planarization of the substrate surface of this invention. It is a figure which shows the CMP apparatus which implemented this invention. It is explanatory drawing which shows the CMP process of this invention.

  The cerium oxide particles in the present invention can be obtained by firing or oxidizing a cerium compound such as carbonate, nitrate, sulfate, or oxalate. In the embodiment of the present invention, as a method for producing the cerium oxide powder, firing or oxidation using hydrogen peroxide or the like can be used. The firing temperature is preferably 350 ° C. or higher and 900 ° C. or lower.

  Since the cerium oxide particles produced by the above method are agglomerated, it is preferably mechanically pulverized. As the pulverization method, a dry pulverization method such as a jet mill or a wet pulverization method such as a planetary bead mill is preferable. The jet mill is described, for example, in Chemical Industrial Papers Vol. 6 No. 5 (1980) pp. 527-532.

  The CMP abrasive is obtained by washing the cerium oxide particles synthesized by the above method and dispersing a composition containing a water-soluble polymer, a complexing agent with cerium, water and, if necessary, a dispersant. . For washing, a method of repeating solid-liquid separation several times by centrifugation or the like can be used.

  The pH of the CMP abrasive is preferably 3 or more and 9 or less, more preferably 5 or more and 8 or less. When the pH is less than 3, the chemical action becomes small and the polishing rate decreases. When the pH is higher than 9, the particles are aggregated to reduce the contact area with the film to be polished, and the polishing rate tends to decrease. Moreover, since it uses for semiconductor chip grinding | polishing, it is preferable to suppress the content rate of an alkali metal and halogens to 10 ppm or less in a cerium oxide particle.

  It is generally considered that the cerium oxide particles dispersed in water are not completely separated one by one, and the measured particle size of cerium oxide dispersed in water is taken by SEM photography in the powder state. It becomes larger than the primary particle diameter measurement value obtained by using the above method.

  The secondary particle diameter of cerium oxide dispersed in water is desirably 1 nm or more and 300 nm or less. When the secondary particle diameter is smaller than 1 nm, the influence on the film to be polished as abrasive grains decreases, and the polishing rate decreases. When the secondary particle diameter is larger than 300 nm, the contact area with the film to be polished becomes small and the polishing rate tends to decrease. The particle diameter is measured by a photon correlation method (for example, Zetasizer 3000HS manufactured by Malvern).

  Moreover, the primary particle diameter of cerium oxide needs to be larger than 0 nm and not larger than 300 nm. When the primary particle diameter is 0 nm, the silicon oxide film is not polished at all. On the other hand, if the crystallite diameter is larger than 300 nm, the secondary particle diameter is larger than 300 nm and the polishing rate is lowered. Although there is no restriction | limiting in the density | concentration of a cerium oxide particle, The range of 0.5 weight% or more and 20 weight% or less is preferable from the ease of handling of a dispersion liquid.

  Examples of water-soluble polymers include polyvinyl sulfonic acid, polymethacrylic acid, polystyrene sulfonic acid, polyacrylic acid, polyacrylic acid derivatives, poly (4-vinylpyridinium salt), poly (1 (3-sulfonyl) -2-vinylpyridinium Betaine-co-p-styrenesulfonic acid), polyvinyl alcohol derivatives, polyacrolein, poly (vinyl acetate-co-methyl methacrylate), poly (styrene-co-maleic anhydride), poly (olefin-co-maleic anhydride) ), Polyacrylamide partial hydrolyzate, poly (acrylamide-co-acrylic acid), alginic acid, polymethyl acrylate, polymethyl methacrylate, and polyacrylic acid or polymethacrylic acid ammonium salt, amine salt or potassium salt, etc. Water-soluble anionic field At least one selected from activators; water-soluble nonionic surfactants such as polyvinyl pyrrolidone can be used, and preferably polymethacrylic acid, polyacrylic acid, polyvinyl alcohol derivatives, polyacrylamide partial hydrolysates Poly (acrylamide-co-acrylic acid), ammonium salt or amine salt of polyacrylic acid or polymethacrylic acid can be used. Examples of amine salts include salts with N, N-dimethylaminoethanol. In addition, the weight average molecular weight (value measured by GPC and converted to standard polystyrene) of the water-soluble polymer is preferably 1,000 to 100,000.

  The ratio of the number of moles of monomer units of the water-soluble polymer / number of moles of the water-soluble polymer and the amine that forms the salt is not particularly limited, but the pH of the abrasive must be 3 or more and 9 or less, so that it is 10/7 or more. It is preferable that it is 10/14 or less. The water-soluble polymer needs to be mixed with the CMP abrasive so that the amount thereof is 1 to 3 times the weight of the cerium oxide particles. If it is less than 1 times by weight, the effect of the water-soluble polymer is diminished, resulting in poor flattening characteristics. If it exceeds 3 times by weight, the polishing rate tends to be low. Moreover, it is preferable that the density | concentration of water-soluble polymer is 1-5 weight from points, such as handleability and mixing workability | operativity.

The complexing agent with cerium is not particularly limited as long as it can form a complex with cerium. For example, α-diketone, general formula (I)
(Wherein R ¹ and R ² represent a substituted or unsubstituted alkyl group, and R ³ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms) β-diketone, γ- At least one selected from diketones such as diketones and diamines such as ethylenediamine and ethylenediaminetetraacetic acid can be used, and β-diketones are preferred because of their high complex-forming ability.

In general formula (I), R ¹ and R ² represent a substituted or unsubstituted alkyl group, and considering that it is handled as an aqueous abrasive solution, water having 1 to 3 carbon atoms that are more polar and hydrophilic is water. It is more preferable in terms of its high solubility in water, and a methyl group is particularly preferable. R ³ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms, and is preferably a hydrogen atom or a methyl group in consideration of handling as an aqueous abrasive solution. preferable. That is, 2,4-pentanedione (common name: acetylacetone) in which R ¹ and R ² are methyl groups and R ³ is H is particularly preferable. The complex formation between the β-diketone represented by the general formula (I) and the cerium particles is represented by the general formula (II).
(Wherein R ¹ , R ² and R 3 have the same meaning as in general formula (I)). When complexed on the surface of the cerium oxide particles in this way, the surface of the cerium particles is covered with a hydrophobic organic functional group, so the interaction with a film having a hydrophilic metal such as silicon oxide on the surface is reduced, It is estimated that the effect of preventing adhesion of cerium oxide particles to the silicon oxide film surface is exhibited.

  The concentration of the complexing agent is required to be 0.1% by weight or more and 10% by weight or less from the viewpoints of handleability and mixing workability in consideration of solubility in water, and 0.5% by weight or more. More preferably, it is 2% by weight or less. If it is less than 0.1% by weight, the amount of addition to cerium tends to be insufficient, and the desired effect of reducing polishing scratches tends not to be obtained. If it is more than 10% by weight, the solubility in water may be reduced.

  As the CMP abrasive, it is possible to use a dispersion obtained by adding a dispersant to the abrasive as necessary. As the dispersant, in addition to the water-soluble polymer described above, at least one selected from a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, and a water-soluble amphoteric dispersant. Two or more types of dispersants containing can be used.

  Examples of the water-soluble anionic dispersant include lauryl sulfate triethanolamine, ammonium lauryl sulfate, and polyoxyethylene alkyl ether sulfate triethanolamine. An anionic water-soluble polymer described later may be used.

  Examples of the water-soluble nonionic dispersant include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether, Polyoxyethylene nonylphenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivative, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, Polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polytetraoleate Carboxymethyl sorbit, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkyl amines, polyoxyethylene hardened castor oil, and alkyl alkanolamides.

  Examples of the water-soluble cationic dispersant include coconut amine acetate and stearylamine acetate. Examples of the water-soluble amphoteric dispersant include lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, and 2-alkyl- N-carboxymethyl-N-hydroxyethyl imidazolinium betaine etc. are mentioned.

  These dispersant addition amounts are in the range of 0.01 parts by weight or more and 2.0 parts by weight or less with respect to 100 parts by weight of the cerium oxide particles from the relationship between dispersibility and settling prevention, as well as polishing scratches and dispersant addition amount. Is preferred. 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.

  Examples of a method for manufacturing an inorganic insulating film to be polished using a CMP abrasive include a constant pressure CVD method and a plasma CVD method.

Formation of the silicon oxide insulating film by the constant pressure CVD method uses monosilane: SiH ₄ as the Si source and oxygen: O ₂ as the oxygen source. It can be obtained by performing this SiH ₄ —O ₂ -based oxidation reaction at a low temperature of about 400 ° C. or less. When doping phosphorus: P in order to achieve surface flattening by high-temperature reflow, it is preferable to use a SiH ₄ —O ₂ —PH ₃ -based reactive gas.

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

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

  As shown in FIGS. 1A and 1B, the substrate is oxidized on a semiconductor substrate such as a semiconductor substrate, that is, a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed, or a semiconductor substrate at a stage where a circuit element is formed. A substrate on which a silicon film or a silicon oxide film and a silicon nitride film are formed can be used. By polishing the silicon oxide film layer formed on such a semiconductor substrate with the above-mentioned polishing agent, unevenness on the surface of the silicon oxide film layer is eliminated, and a smooth surface is formed over the entire surface of the semiconductor substrate.

  Specifically, a CMP chip containing cerium oxide particles, a water-soluble polymer, a complexing agent with cerium and water is supplied to a polishing pad on a polishing surface plate, and a semiconductor chip on which a silicon oxide insulating film is formed. The surface to be polished is brought into contact with the surface to be polished of a substrate and the surface to be polished and the polishing pad are moved relative to each other to polish the surface of the substrate through the cerium oxide particles complexed on the surface.

  In the case of shallow trench isolation, only the silicon oxide film embedded in the element isolation portion is left by polishing the underlying silicon nitride layer while eliminating the unevenness of the silicon oxide film layer. At this time, if the polishing rate ratio with the silicon nitride serving as a stopper is large, the polishing process margin becomes large. In addition, in order to use for shallow trench isolation, it is also necessary to reduce the generation of scratches during polishing.

  Here, as a polishing apparatus, a general polishing apparatus having a surface plate with a holder for holding a semiconductor substrate and a polishing cloth (pad) attached (a motor etc. capable of changing the number of rotations) is used. it can. FIG. 2 is a schematic view showing a CMP apparatus used in the present invention. A CMP polishing agent containing cerium oxide particles, a water-soluble polymer, a complexing agent with cerium, and water is supplied onto a polishing pad 17 affixed on a polishing surface plate 18, and a substrate 13 which is a semiconductor chip. The silicon oxide insulating film 14 formed on the surface is attached to the wafer holder 11 as a surface to be polished, the silicon oxide insulating film 14 is brought into contact with the polishing pad, and the surface to be polished and the polishing pad are moved relative to each other. The surface plate 18 is rotated to perform CMP, that is, polishing of the substrate.

As the polishing pad, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used, and there is no particular limitation. Further, it is preferable that the polishing pad is subjected to groove processing so that an abrasive is collected. The polishing conditions are not limited, but the rotation speed of the surface plate is preferably low rotation of 100 min ⁻¹ or less so that the semiconductor does not jump out. The pressure applied to the polishing pad of the semiconductor substrate having the film to be polished is preferably 10 to 100 kPa, and 20 to 50 kPa to satisfy the uniformity of the polishing rate within the wafer surface and the flatness of the pattern. Is more preferable. During polishing, a polishing agent is continuously supplied to the polishing pad by a pump or the like. Although there is no restriction | limiting in this supply amount, It is preferable that the surface of a polishing pad is always covered with the abrasive | polishing agent.

  FIG. 3 shows a CMP process in the present invention. In order to perform CMP with the surface state of the polishing pad always kept the same, a polishing pad conditioning step is inserted before CMP. Specifically, polishing is performed with a liquid containing at least water using a dresser with diamond particles. Subsequently, the polishing process of the present invention was performed, and 1) brush cleaning for removing foreign substances such as particles adhering to the substrate after polishing, 2) megasonic cleaning for replacing the abrasive and the like with water, 3) Add a wafer cleaning process consisting of spin drying to remove water from the substrate surface.

  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. Thus, after shallow trench isolation is formed on the Si substrate, a silicon oxide insulating film layer and an aluminum wiring are formed thereon, and the silicon oxide insulating film formed thereon is planarized. A second-layer aluminum wiring is formed on the planarized silicon oxide insulating film layer, and a silicon oxide film is formed again between the wirings and on the wiring by the above method, followed by polishing with the above-described polishing agent. As a result, unevenness on the surface of the silicon oxide insulating film is eliminated, and a smooth surface is obtained over the entire surface of the semiconductor substrate. By repeating this process a predetermined number of times, a desired number of semiconductor layers are manufactured.

  CMP abrasives are not only silicon oxide films and silicon nitride films formed on semiconductor substrates, but also silicon oxide films formed on wiring boards having predetermined wiring, glass, inorganic insulating films such as silicon nitride, photomasks Optical single crystals such as optical glass such as lenses and prisms, inorganic conductive films such as ITO, glass, and crystalline materials, optical integrated circuits, optical switching elements, optical waveguides, end faces of optical fibers, scintillators, etc. It is used for polishing substrates such as solid laser single crystals, LED sapphire substrates for blue lasers, semiconductor single crystals such as SiC, GaP, and GaAS, glass substrates for magnetic disks, and magnetic heads.

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

Example 1
(Preparation of Additive Solution A) A polyacrylic acid ammonium salt having a weight average molecular weight of 6000, the number of moles of ammonium ions / the number of moles of carboxyl groups in polyacrylic acid = 1 was diluted with deionized water, and a 3 wt% aqueous solution. (Addition liquid A).

(Preparation of Additive Solution B) 2 kg of cerium carbonate hydrate was placed in a platinum container and baked in air at 850 ° C. for 2 hours to obtain about 1 kg of yellowish white cerium oxide particles. 1 kg of the cerium oxide particles prepared above, 10 g of acetylacetone, 23 g of an aqueous solution of ammonium polyacrylate (weight average molecular weight 15000, 40% by weight) and 8967 g of deionized water were mixed and subjected to ultrasonic dispersion for 10 minutes while stirring. The obtained slurry was filtered through a 1 μm filter, and further deionized water was added to dilute it twice (cerium oxide particle concentration 5 wt%).

(Preparation of polishing agent) The above-mentioned additive solution A / addition solution B / deionized water was mixed at a weight ratio of 2/1 to prepare a CMP polishing agent having a cerium oxide particle concentration of 1.7% by weight and a polymer concentration of 2% by weight. did. The pH of the abrasive was 6.8. When the secondary particle diameter was measured by a photon correlation method using an abrasive stock solution, the median value was 270 nm.

(Polishing of insulating film layer and shallow trench isolation layer) After forming an Al wiring Line portion having a Line / Space width of 0.05 to 5 mm and a height of 1000 nm on an 8-inch Si substrate, TEOS-plasma CVD is performed thereon. An insulating film layer pattern wafer in which a silicon oxide film is formed to 2000 nm by this method is produced. Polishing was performed with the above CMP abrasive for 3 minutes (rotation speed of platen: 50 min ⁻¹ , polishing load: 30 kPa, abrasive supply amount: 200 ml / min). As a result, the level difference between the convex and concave portions after polishing was 40 nm, indicating high flatness.

Further, as shown in FIG. 1 (a), convex portions with sides of 350 nm to 0.1 mm square and concave portions with a depth of 400 nm are formed on an 8-inch Si substrate so that the density of the convex portions is 2 to 40%, respectively. A shallow trench isolation layer pattern wafer was fabricated. Subsequently, as shown in FIG. 1B, a nitric oxide film having a thickness of 100 nm was formed on the convex portion, and a silicon oxide film having a thickness of 600 nm was formed thereon by TEOS-plasma CVD. The patterned wafer was polished for 2 minutes with the above-described CMP abrasive (plate rotation speed: 50 min ⁻¹ , polishing load: 30 kPa, abrasive supply amount: 200 ml / min). As a result, as shown in FIG. 1C, the polishing of the convex portion was stopped by the silicon nitride film, and the level difference after the polishing was 40 nm, indicating high flatness. No scratches were observed in any polishing.

(Polishing of insulating film layer blanket wafer) Next, the 8-inch silicon oxide film blanket wafer and the silicon nitride blanket wafer were each polished with the above-described CMP abrasives (rotation speed of platen: 50 min ⁻¹ , polishing load: 30 kPa, polishing) (Agent supply amount: 200 ml / min). After polishing, the wafer was removed from the holder and washed with a PVA sponge brush while flowing deionized water. After cleaning, the wafer was rotated on a spin dryer at 1000 min ⁻¹ for 1 minute to remove water droplets. Finally, the foreign matter on the surface of the dried wafer was counted using a laser scattering type foreign matter inspection apparatus.

  As a result, with respect to the silicon oxide film, the polishing rate was 150 nm / min, and there were 30 foreign matters of 0.2 μm or more per wafer. Further, with respect to the silicon nitride film, the polishing rate was 5 nm / min, and there were 50 foreign matters of 0.2 μm or more per wafer. In addition, no polishing scratches were observed in any polishing.

Example 2
(Preparation of abrasive) Same as Example 1 except that the amount of acetylacetone used in the preparation of additive liquid B in Example 1 was changed from 10 g to 1000 g, and the amount of deionized water was changed from 8967 g to 7777 g accordingly. A CMP abrasive was prepared. The pH of the abrasive was 6.6, and the median secondary particle size was 250 nm.

(Polishing of Insulating Film Layer and Shallow Trench Separation Layer) Using the CMP abrasive prepared as described above, the same insulating film layer pattern wafer as in Example 1 was polished for 5 minutes under the same polishing conditions. As a result, the level difference between the convex and concave portions after polishing was 55 nm.

  Further, using the above-described CMP abrasive, a nitrogen oxide film having a thickness of 100 nm is formed on the convex portion of the shallow trench isolation layer pattern wafer in the same manner as in Example 1, and a silicon oxide film having a thickness of 600 nm is formed thereon by TEOS-plasma CVD. The film was polished for 4 minutes under the same polishing conditions as in Example 1. As a result, the level difference after polishing was 42 nm, indicating high flatness. No scratches were observed in any polishing.

(Polishing of insulating film layer blanket wafer) Next, the same 8-inch silicon oxide film blanket wafer and silicon nitride film blanket wafer as in Example 1 were also subjected to the same polishing conditions as in Example 1 using the above-described CMP abrasive. Each was polished.

  As a result, for the silicon oxide film, the polishing rate was 80 nm / min, and there were 20 foreign matters of 0.2 μm or more per wafer. The silicon nitride film had a polishing rate of 6 nm / min, and there were 40 foreign matters of 0.2 μm or more per wafer. In addition, no polishing scratches were observed in any polishing.

Comparative Example 1
(Preparation of abrasive) Same as Example 1, except that acetylacetone used in preparation of additive liquid B of Example 1 is eliminated from 10 g → 0 and the amount of deionized water is changed from 8967 g → 8977 g accordingly. Thus, a CMP abrasive was prepared. The pH of the abrasive was 6.8, and the median secondary particle size was 280 nm.

(Polishing of Insulating Film Layer and Shallow Trench Separation Layer) Using the CMP abrasive prepared as described above, the same insulating film layer pattern wafer as in Example 1 was polished for 3 minutes under the same polishing conditions. As a result, the level difference between the convex and concave portions after polishing was 45 nm.

  Further, using the above-described CMP abrasive, a nitrogen oxide film having a thickness of 100 nm is formed on the convex portion of the shallow trench isolation layer pattern wafer in the same manner as in Example 1, and a silicon oxide film having a thickness of 600 nm is formed thereon by TEOS-plasma CVD. The film was polished for 2 minutes under the same polishing conditions as in Example 1. As a result, the level difference after polishing was 40 nm, indicating high flatness. No scratches were observed in any polishing.

(Polishing of insulating film layer blanket wafer) Next, the same 8-inch silicon oxide film blanket wafer and silicon nitride film blanket wafer as in Example 1 were also subjected to the same polishing conditions as in Example 1 using the above-described CMP abrasive. Each was polished.

  As a result, with respect to the silicon oxide film, the polishing rate was 160 nm / min, and there were 200 foreign matters of 0.2 μm or more per wafer. Further, with respect to the silicon nitride film, the polishing rate was 6 nm / min, and there were 200 foreign matters of 0.2 μm or more per wafer. As for the scratches caused by polishing, slight scratches were observed only on the silicon oxide film blanket wafer.

  Example 1 using CMP abrasive containing cerium oxide particles, water-soluble polymer, complexing agent with cerium and water having concentration of complexing agent with cerium of 0.1 wt% or more and 10.0 wt% or less On the other hand, Comparative Example 1 is equivalent in terms of the polishing rate, but is inferior in the performance of removing foreign matter, that is, particles by cleaning after polishing. Also, with respect to polishing scratches, Example 1 was superior to Comparative Example 1, and it was found that a high polishing rate, high flatness, and low polishing scratches could be achieved.

DESCRIPTION OF SYMBOLS 1 Si substrate 2 Silicon nitride film 3 Silicon oxide film 11 Wafer holder 12 Retainer 13 Substrate which is a semiconductor chip 14 Silicon oxide insulating film 15 Abrasive supply mechanism 16 Cerium oxide particles, water-soluble polymer, complexing agent with cerium and water Including abrasive 17 Polishing pad 18 Polishing surface plate

Claims (4)

A CMP abrasive for removing an excess silicon oxide film,
Cerium oxide particles, water-soluble polymer, complexing agent with cerium selected from β-diketone and water,
The complexing agent is represented by the general formula (I)

( Wherein R ¹ and R ² represent a substituted or unsubstituted alkyl group, and R ³ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms),
Ri complexing agent concentration of 0.1 wt% to 10.0 wt% der less of cerium, and
A CMP abrasive having a pH of 8 or less . CMP abrasive of claim 1 Symbol placement complexing agent is acetylacetone. C MP polishing agent according to claim 1 or 2 is at least one water-soluble polymer is selected the group consisting of water soluble anionic surfactant and water-soluble nonionic surfactant. A CMP abrasive according to any one of claims 1 to 3 is supplied to a polishing pad on a polishing surface plate and brought into contact with a surface to be polished of a substrate which is a semiconductor chip on which a silicon oxide insulating film is formed. A polishing method for a substrate, wherein a polishing surface and a polishing pad are moved relative to each other to polish the substrate surface through cerium oxide particles complexed on the surface, thereby removing an excess silicon oxide insulating film.