Abrasive and polishing method

Abstract

To provide an abrasive in which the polishing speed of a silicon surface is suppressed.SOLUTION: An abrasive includes abrasive grains and a compound represented by the following formula (1). R-O-(AO)n-H (1). In the formula, R is an organic group containing a conjugated system and may have a heteroatom in a carbon skeleton. When, among the atoms constituting the carbon skeleton, the number of atoms constituting the conjugated system is C1 and the number of atoms that do not constitute the conjugated system is C2, C1 / (C1+C2)≥0.4 is satisfied, and AO represents an oxyalkylene group, and a plurality of AOs may be the same or different from each other, and n is an integer from 2 to 200.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an abrasive and a polishing method, and more particularly to an abrasive and a polishing method for chemical mechanical polishing in the manufacture of semiconductor integrated circuits. [Background technology]

[0002] In recent years, with the increasing integration and functionality of semiconductor integrated circuits, microfabrication technology has been developed to miniaturize and increase the density of semiconductor elements. Conventionally, in the manufacture of semiconductor integrated circuit devices (hereinafter also referred to as semiconductor devices), interlayer insulating films, buried wiring, etc. have been planarized using chemical mechanical polishing (hereinafter referred to as CMP) to prevent problems such as the unevenness (step) of the layer surface exceeding the focal depth of lithography, making it impossible to obtain sufficient resolution. As the demand for high definition and miniaturization of elements becomes stricter, the importance of high planarization by CMP is increasing.

[0003] Furthermore, in recent years, in the manufacture of semiconductor devices, a method of isolation using shallow trenches with a small element isolation width (hereinafter referred to as STI) has been introduced in order to advance the more advanced miniaturization of semiconductor elements. STI is a technique for forming an electrically insulated device region by forming a trench in a silicon substrate and filling the trench with an insulating film. An example of STI will be described with reference to FIG. 1. In the example of FIG. 1, first, as shown in FIG. 1(a), a device region of a silicon substrate 1 is masked with a silicon nitride film 2 or the like, and then a trench 3 is formed in the silicon substrate 1, and an insulating film such as a silicon dioxide film 4 is deposited so as to fill the trench 3. Next, the silicon dioxide film 4 on the silicon nitride film 2, which is a protruding portion, is polished and removed by CMP while leaving the silicon dioxide film 4 in the trench 3, which is a recessed portion, to obtain a device isolation structure in which the silicon dioxide film 4 is filled in the trench 3, as shown in FIG. 1(b).

[0004] In the CMP for STI, the selectivity between the silicon dioxide film and the silicon nitride film (meaning the ratio of the polishing speed of the silicon dioxide film to the polishing speed of the silicon nitride film) is increased, so that the polishing can be stopped when the silicon nitride film is exposed. In this way, the polishing method using the silicon nitride film as a stopper film can obtain a smoother surface than normal polishing methods.

[0005] In recent years, CMP technology has been studied to suppress the progress of polishing by using the silicon substrate surface instead of a stopper film, and cases where silicon nitride films, in addition to silicon dioxide films, are to be removed are also being considered.

[0006] When a silicon (including polysilicon and amorphous silicon) surface is used as a stopper film, the polishing rate of silicon relative to the film to be removed must be reduced.

[0007] For example, Patent Document 1 discloses a CMP slurry containing a nonionic surfactant having a hydrophilic portion and a lipophilic portion, the hydrophilic portion having a number average molecular weight of 500 g / mol or more. According to Patent Document 1, the nonionic surfactant suppresses the polishing rate of the silicon-containing substrate surface.

[0008] Patent Document 2 discloses a CMP polishing liquid for polishing silicon oxide of a substrate having silicon oxide and silicon nitride or polysilicon as a stopper film, the CMP polishing liquid containing (1) a surfactant with HLB≧17.5, (2) an inorganic abrasive, and (3) a water-soluble organic polymer other than the surfactant in (1). Patent Document 2 states that the surfactant makes it possible to achieve high-speed polishing of the silicon oxide film while maintaining a high selectivity between the polishing speed of the silicon oxide film and polysilicon. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 5628802 [Patent Document 2] Patent No. 5444625 Summary of the Invention [Problem to be solved by the invention]

[0010] The present inventors have found that when polishing a patterned wafer having a patterned trench formed on a silicon substrate and having an insulating film within the trench, even when a surfactant described in Patent Document 1 or Patent Document 2 is used, the silicon surface may be polished and the selectivity between the silicon surface and the insulating film may be insufficient.

[0011] The present invention has been made in view of the above circumstances, and has an object to provide an abrasive and a polishing method that can suppress the polishing rate of the silicon surface even in the case of a patterned wafer. [Means for solving the problem]

[0012] The polishing agent according to the present invention contains abrasive grains and a compound represented by the following formula (1). RO-(AO) n -H formula (1) provided that R is an organic group containing a conjugated system and may have a heteroatom in the carbon skeleton, and when, among the atoms constituting the carbon skeleton, the number of atoms constituting the conjugated system is C1 and the number of atoms not constituting the conjugated system is C2, C1 / (C1+C2)≧0.4; AO represents an oxyalkylene group, and a plurality of AO may be the same or different. n is an integer from 2 to 200.

[0013] In the above abrasive, R may have an aryl group.

[0014] In the above abrasive, in the RO bond of the formula (1), the atom on the R side may be a carbon atom constituting the aryl group.

[0015] In the above abrasive, R may be a hydrocarbon group.

[0016] In the above polishing agent, the compound represented by the formula (1) may have an HLB value of 12-20.

[0017] The abrasive may be such that the abrasive grains are metal oxide particles.

[0018] The abrasive may further contain a polymer.

[0019] In the abrasive, the polymer may include an anionic polymer.

[0020] In the above abrasive, the anionic polymer may have an aryl group.

[0021] The polishing agent may have a pH of 2-7.

[0022] The above abrasives can be used to expose a patterned surface, including a silicon surface, on the surface.

[0023] The polishing method of the present invention is a polishing method in which a surface to be polished is brought into contact with a polishing pad while an abrasive is supplied, and polishing is performed by relative movement of the two, and is characterized in that the abrasive is used as the abrasive to polish a surface to be polished, including a surface of a semiconductor substrate made of silicon oxide.

[0024] The polishing method may be such that a pattern surface including a silicon surface is exposed on the surface of the semiconductor substrate. Effect of the Invention

[0025] The present invention provides a polishing agent and a polishing method that suppress the polishing rate of a silicon surface. [Brief description of the drawings]

[0026] [Figure 1] 1 is a cross-sectional view showing an example of a semiconductor substrate to be polished by CMP in STI. [Diagram 2] FIG. 2 is a schematic cross-sectional view for explaining the action of the present abrasive. [Diagram 3] FIG. 2 is a schematic diagram showing an example of a polishing apparatus. [Figure 4] FIG. 2 is a schematic cross-sectional view showing a substrate used in evaluating a pattern removal rate and the polishing process thereof in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, the embodiments of the present invention will be described. The present invention is not limited to the following embodiments, and other embodiments may also fall within the scope of the present invention as long as they correspond to the gist of the present invention.

[0028] In the present invention, the term "surface to be polished" refers to the surface to be polished of an object to be polished, for example, the surface. In this specification, the term "surface to be polished" also includes intermediate surfaces that appear on a semiconductor substrate during the process of manufacturing a semiconductor device. In the present invention, "silicon oxide" specifically refers to silicon dioxide, but is not limited thereto and also includes silicon oxides other than silicon dioxide. In the present invention, the "selectivity" refers to the polishing rate (R A ) membrane B The polishing speed (R B ) to the ratio (R A / R B ) Furthermore, the symbol "~" indicating a range of numerical values ​​includes the numerical values ​​before and after it as the lower and upper limits. For clarity of explanation, the following description and drawings are simplified as appropriate. Also, the scale of each component in the drawings may differ significantly for the purpose of explanation. In particular, the uneven shape of the polishing surface is extremely exaggerated.

[0029] [Abrasive] The polishing agent according to the present invention (hereinafter also referred to as the present polishing agent) is characterized by containing abrasive grains and a compound represented by the following formula (1) (hereinafter also referred to as compound (1)). RO-(AO) n -H formula (1) provided that R is an organic group containing a conjugated system and may have a heteroatom in the carbon skeleton, and when, among the atoms constituting the carbon skeleton, the number of atoms constituting the conjugated system is C1 and the number of atoms not constituting the conjugated system is C2, C1 / (C1+C2)≧0.4; AO represents an oxyalkylene group, and a plurality of AO may be the same or different. n is an integer from 2 to 200.

[0030] According to the present invention, a polishing agent that suppresses the polishing rate of the silicon surface while maintaining the polishing rate of the film to be polished even in the case of a patterned wafer can be obtained. Although some aspects of its function are not yet understood, it is speculated as follows. Figure 2 is a schematic cross-sectional view to explain the action of this polishing compound. When polishing is started from the state of Figure 2(A) with the goal of Figure 2(B), in a normal manufacturing process, it is often impossible to stop polishing the moment the state of Figure 2(B) is reached, and polishing continues further. At this time, the silicon surface may be scraped off. In contrast, for example, when a nonionic surfactant described in Patent Document 1 is used, the nonionic surfactant is said to cover the silicon surface, thereby suppressing the polishing of the silicon surface. However, in the case of a patterned wafer in which a silicon nitride film or silicon oxide film and silicon are arranged in a pattern, the selectivity between the silicon nitride film or silicon oxide film and silicon becomes large, and as a result, the surface to be polished may be over-polished, resulting in the formation of a recess (dishing) on ​​the surface, as shown in FIG. 2(C). If the polishing process is continued from this state, it is estimated that a large load will be applied to the edge of the silicon surface. As a result, it is estimated that the silicon surface will be polished from the edge as shown in FIG. 2(D), and the polishing of the silicon surface will proceed. Compound (1) contained in this polishing agent has a conjugated system. It is presumed that the π electrons of the conjugated system interact with the silicon nitride or silicon oxide to be polished, causing the conjugated system of compound (1) to be adsorbed onto the film surface. This is presumed to reduce the polishing rate of the film to be polished, thereby suppressing the formation of dishing. Furthermore, since the polyoxyalkylene group of compound (1) has a high affinity for silicon, it is presumed that the conjugated system of a portion of compound (1) is adsorbed onto silicon nitride or silicon oxide, and the polyoxyalkylene group is adsorbed onto the silicon substrate, protecting the edge of the silicon surface. For this reason, the polishing rate of the silicon surface of a patterned wafer can be effectively suppressed.

[0031] The polishing agent according to the present invention contains at least abrasive grains and compound (1), and may further contain other components within the scope of the above-mentioned effects of the present invention. Each component that may be contained in the polishing agent will be described in detail below.

[0032] <Compound (1)> The present polishing agent contains the compound represented by the above formula (1). R is an organic group containing a conjugated system. Examples of the conjugated system include a carbon-carbon double bond, a carbon-carbon triple bond, an aryl group, and a combination thereof. Specific examples of the combination include an acetylene group, an ethylene group, a polyacetylene, a phenylethenyl group, a biphenyl group, and a terphenyl group. Compound (1) may have one conjugated system or two or more conjugated systems. Examples of the conjugated system having two or more conjugated systems include a structure in which two or more aryl groups, such as a cumylphenyl group, are linked by an alkyl group. All of these conjugated systems are adsorbed to silicon nitride films and silicon oxide films. In terms of the large coverage area and the stability of compound (1), the conjugated system preferably contains an aryl group. The aryl group may be an aromatic hydrocarbon ring group such as a phenyl group, a naphthyl group, an anthracenyl group, or a pyrenyl group, or an aromatic heterocyclic group such as a furyl group, a thiophenyl group, or a pyridyl group. The aryl group may have a hydrocarbon group as a substituent. Examples of the alkyl group include an alkyl group having 1 to 20 carbon atoms that may have a branch, may have a phenyl group as a substituent, or may have a heteroatom. Examples of the heteroatom that R may have include an oxygen atom, a nitrogen atom, a sulfur atom, and a silicon atom. The heteroatom is preferably contained in an aryl group. R is preferably a hydrocarbon group that does not have a heteroatom in terms of structural stability and ease of adsorption to silicon nitride or silicon oxide. When R has an aryl group, the carbon atom constituting the aryl group is -O-(AO) n Bonding to an oxygen atom of -H is preferable from the viewpoint of adsorption to silicon nitride or silicon oxide, and to a silicon surface.

[0033] R satisfies C1 / (C1+C2)≧0.4, where C1 is the number of atoms constituting a conjugated system among the atoms (carbon atoms + heteroatoms) constituting the carbon skeleton, and C2 is the number of atoms not constituting a conjugated system. Since the atoms constituting a conjugated system are 40% or more, the compound has excellent adsorption properties to silicon nitride and silicon oxide. The upper limit of C1 / (C1+C2) may be 1 or less, preferably 0.9 or less, and more preferably 0.8 or less.

[0034] The oxyalkylene group of AO may be an oxyalkylene group having 1 to 6 carbon atoms. From the standpoint of hydrophilicity and adsorptivity to a silicon surface, an oxyethyl group (-OCH2CH2-) or an oxypropyl group (-OCH2CH2CH2- or -OCH2CH(CH3)-) is preferred, with an oxyethyl group being more preferred. The number of repeating units n of AO may be 2 to 200. From the viewpoints of hydrophilicity and adsorptivity to silicon surfaces, it is preferably 5 or more, and more preferably 10 or more. On the other hand, n is sufficient when it is 200 or less, and from the viewpoints of ease of production, it is preferably 180 or less, and more preferably 150 or less.

[0035] The compound (1) preferably has an HLB value of 12 to 20. If the HLB value is 12 or more, the compound is stably dispersed or dissolved in water, and therefore has excellent uniformity in the polishing agent. In the present invention, the HLB value is a value determined by the Griffin method, and when two or more types of compound (1) are used in combination, the average value is used.

[0036] Specific examples of suitable compounds (1) include the following compounds. In the formula below, AO and n are the same as those in formula (1). In addition, C1 / (C1+C2) of compound (1-1) is 0.4, C1 / (C1+C2) of compound (1-2) is 0.8, and C1 / (C1+C2) of compound (1-3) is 1.

[0037] [ka]

[0038] Compound (1) may be obtained by synthesis, or a commercially available product may be used. As an example, compound (1) can be obtained by addition polymerization of alkylene oxide such as ethylene oxide or propylene oxide to the following compound (2). R in formula (2) is the same as that in formula (1), and the preferred embodiments are also the same. R-OH formula (2)

[0039] The content of compound (1) in the polishing agent is preferably 0.001% by mass to 1% by mass, more preferably 0.005% by mass to 0.5% by mass, based on the total amount of the polishing agent. By making the content 0.001% by mass or more, the polishing rate of silicon is sufficiently suppressed. On the other hand, by making the content 1% by mass or less, the polishing agent has excellent dispersibility and dispersion stability of the abrasive grains.

[0040] <Abrasive grain> The polishing agent contains abrasive grains. The abrasive grains can be appropriately selected from those used as abrasive grains for CMP. From the viewpoint of excellent polishing speed for silicon nitride and silicon oxide, the abrasive grains are preferably metal oxide particles. The metal oxide may be selected from the group consisting of cerium oxide, alumina, silica, titania, and zirconia. Of these, cerium oxide is preferred because of its excellent polishing rate for silicon nitride and silicon oxide.

[0041] The cerium oxide particles for the abrasive grains can be appropriately selected from known ones. For example, cerium oxide particles manufactured by the methods described in JP-A-11-12561, JP-A-2001-35818, and JP-T-2010-505735 can be mentioned. Specifically, cerium oxide particles obtained by adding an alkali to an aqueous solution of cerium (IV) ammonium nitrate to prepare a cerium hydroxide gel, which is then filtered, washed, and fired; cerium oxide particles obtained by crushing high-purity cerium carbonate, firing it, crushing it, and classifying it; and cerium oxide particles obtained by chemically oxidizing cerium (III) salt in a liquid can be mentioned.

[0042] The average particle size of the metal oxide particles is preferably 0.01 to 0.5 μm, more preferably 0.03 to 0.3 or less. If the average particle size is 0.5 μm or less, the occurrence of polishing flaws such as scratches on the polished surface is suppressed. In addition, if the average particle size is 0.01 μm or more, coarse particle aggregation is suppressed, and the storage stability of the polishing agent is excellent, and the polishing rate is also excellent. Since metal oxide particles exist in liquid as aggregated particles (secondary particles) formed by aggregation of primary particles, the preferred particle size of the metal oxide particles is expressed as the average secondary particle size. That is, the average particle size shown in the above numerical range is usually the average secondary particle size. The average secondary particle size is measured using a particle size distribution analyzer such as a laser diffraction / scattering type using a dispersion liquid in which the particles are dispersed in a dispersion medium such as pure water.

[0043] The content (concentration) of the abrasive grains is preferably 0.05 to 2.0 mass % relative to the total mass of the polishing agent, and more preferably 0.10 to 0.5 mass %. When the content of the abrasive grains is equal to or greater than the lower limit, an excellent polishing rate can be obtained. On the other hand, when the content of the abrasive grains is equal to or less than the upper limit, an increase in the viscosity of the polishing agent is suppressed, and the polishing agent is easy to handle.

[0044] <Dispersion medium> The present polishing agent is preferably used in the form of a slurry, and in this case, it usually contains a dispersion medium. The dispersion medium can be appropriately selected from those that are liquid at least at room temperature (25°C), disperse or dissolve compound (1), and can disperse abrasive grains well. In the present polishing agent, it is preferable to use water as the dispersion medium from the viewpoint of excellent handling.

[0045] <Other ingredients> The polishing agent of the present invention may further contain other components within the range in which the above-mentioned effects of the present invention are exhibited. Examples of other components include a pH adjuster, a dispersant, a lubricant, and a polymer. The dispersant is used as necessary to improve the dispersibility and dispersion stability of the abrasive colloid. Examples of the dispersant include anionic, cationic, nonionic, and amphoteric surfactants, and anionic, cationic, nonionic, and amphoteric polymer compounds, and one or more of these may be contained. The lubricant is used as necessary to improve the lubricity of the polishing agent and the in-plane uniformity of the polishing rate. Examples of the lubricant include water-soluble polymers such as polyethylene glycol and polyglycerin.

[0046] (polymer) The polishing agent may contain a polymer. The polymer adsorbs to the abrasive grains or the surface to be polished, thereby suppressing the chemical interaction between the abrasive grains and the surface to be polished, and thus controlling the polishing rate of silicon nitride or silicon oxide. This effect not only allows the polishing rate to be appropriately controlled, but also suppresses dishing that occurs in the silicon nitride film or silicon oxide film after the silicon surface is exposed on the surface. The polymer can be appropriately selected from those that have the above-mentioned effects and can be used alone or in combination of two or more. Among them, it is preferable to use an anionic polymer because it is possible to further reduce the polishing rate of silicon.

[0047] The anionic polymer is preferably a polymer having an acidic group. Examples of the acidic group include a sulfo group, a phospho group, a carboxy group, or a salt thereof. When the object to be polished is a silicon oxide film, a carboxy group is preferable, and when the object to be polished is a silicon nitride film, a sulfo group or a phospho group is preferable because the ionization state is stable even under strong acidity.

[0048] In addition, the anionic polymer preferably has an aryl group. It is presumed that the anionic polymer having an aryl group is adsorbed to the film surface by the π electrons of the aryl group interacting with the silicon nitride or silicon oxide to be polished. This suppresses dishing of the silicon nitride film or silicon oxide film. Furthermore, in this polishing agent, it is presumed that dishing of the silicon nitride film or silicon oxide film is further suppressed by π-π stacking of the aryl group of the anionic polymer and the conjugated system of the compound (1). The aryl group of the anionic polymer may be an aromatic hydrocarbon ring group such as a phenyl group, a naphthyl group, an anthracenyl group, a pyrenyl group, etc., or an aromatic heterocyclic group such as a furyl group, a thiophenyl group, a pyridyl group, etc. From the viewpoint of inhibiting dishing of a silicon nitride film or a silicon oxide film by interacting with compound (1), a phenyl group or a naphthyl group is preferred.

[0049] Specific examples of anionic polymers include polyacrylic acid; styrene-acrylic acid copolymer; styrene-maleic acid copolymer; copolymer of 2-acrylamido-2-methylpropanesulfonic acid and acrylic acid; copolymer of 2-acrylamido-2-methylpropanesulfonic acid and maleic acid; copolymer of 3-allyloxy-2-hydroxy-1-propanesulfonic acid and acrylic acid; copolymer of 3-allyloxy-2-hydroxy-1-propanesulfonic acid and maleic acid; copolymer of 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, and maleic acid; copolymer of 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, and maleic acid; copolymer of acrylic acid; 2-acrylamido Examples of the copolymer include a copolymer of 1-methyl-2-propanesulfonic acid, 3-allyloxy-2-hydroxy-1-propanesulfonic acid, and maleic acid and a copolymer of maleic acid; a sulfonic acid modified polyvinyl alcohol; a copolymer of styrenesulfonic acid and maleic acid; a copolymer of styrenesulfonic acid and styrene; a naphthalenesulfonic acid-formaldehyde condensate; and poly-p-styrenesulfonic acid. Among these, a polymer containing a sulfo group is preferred, a copolymer of styrenesulfonic acid and maleic acid; a copolymer of naphthalenesulfonic acid and formalin condensate; or poly-p-styrenesulfonic acid is more preferred, and a naphthalenesulfonic acid-formaldehyde condensate or poly-p-styrenesulfonic acid is even more preferred. The anionic polymers can be used alone or in combination of two or more.

[0050] When a polymer is used in the polishing agent, the content is preferably 0.0001 to 1 mass % based on the total amount of the polishing agent. Since the effect of the polymer on the polishing speed of a silicon oxide film or a silicon nitride film varies greatly depending on the type of polymer, the amount of the polymer is actually adjusted to achieve a predetermined polishing speed.

[0051] (pH adjuster) The polishing agent may contain a pH adjuster to adjust the pH. The pH adjuster may be appropriately selected from known inorganic acids, organic acids, basic compounds, amphoteric compounds such as amino acids, and salts thereof. Examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, etc., and their ammonium salts, sodium salts, potassium salts, etc. may also be used. Examples of the organic acid include carboxylic acids, organic sulfonic acids, and organic phosphoric acids, and their ammonium salts, sodium salts, potassium salts, and the like may also be used. Examples of the carboxylic acids include acetic acid, propionic acid, lactic acid, tartaric acid, oxalic acid, maleic acid, etc. Examples of the organic sulfonic acids include benzenesulfonic acid, tosylic acid, etc. Examples of the organic phosphoric acids include methylphosphonic acid, dimethylphosphinic acid, etc. Examples of the basic compound include ammonia, potassium hydroxide, tetramethylammonium hydroxide, and ethylenediamine. Examples of amphoteric compounds include glycine, alanine, and phenylalanine.

[0052] Since the polishing agent is preferably used under acidic conditions as described below, the pH adjuster is preferably an acidic substance. In addition, in order to provide a pH buffering ability, it is preferable to use an acid whose pKa is close to the pH range in which the polishing agent is used, and in this sense, carboxylic acid, phosphonic acid, and phosphoric acid are preferable. Among them, phosphoric acid is preferable because it improves the polishing speed of the silicon nitride film.

[0053] The content of the pH adjuster may be appropriately adjusted to the desired pH, for example, 0.005 to 2.0 mass % relative to the entire polishing agent, preferably 0.01 to 1.5 mass %, and more preferably 0.01 to 0.3 mass %.

[0054] The pH of the polishing agent is preferably 7 or less, more preferably 2 to 7. By adjusting the pH to 7 or less, the polishing speed of silicon nitride film and silicon oxide film is improved, and the dispersion stability of the metal oxide particles, which are abrasive grains, is also improved. The pH of the polishing agent is preferably 2 to 6, more preferably 2.0 to 5.5. In particular, when a silicon nitride film is to be polished, a strong acidity of pH 2.0 to 3.5 is preferred to promote hydrolysis of the silicon nitride film.

[0055] <Method of preparing this abrasive> The method for preparing the present polishing agent may be appropriately selected from among methods by which each component that can be contained in the present polishing agent can be uniformly dispersed or dissolved in the dispersion medium. For example, the polishing agent may be prepared by adding abrasive grains, compound (1), and other components used as necessary to a dispersion medium and stirring the mixture, or a dispersion of abrasive grains and a solution of compound (1) may be prepared and then mixed. The mixing may be performed in a polishing apparatus.

[0056] <Polishing method using this abrasive> The polishing method using the present polishing agent includes, for example, a method in which the surface to be polished of the object to be polished is brought into contact with a polishing pad while supplying the present polishing agent, and polishing is performed by the relative movement of the two. Here, the surface to be polished includes, for example, a blanket wafer having a silicon dioxide film or silicon nitride film formed on the front surface of a semiconductor substrate, and a pattern wafer having these film types arranged in a pattern. When a silicon nitride film or a silicon oxide film is polished using this polishing agent, the silicon surface of the semiconductor substrate functions as a stopper film. The silicon surface may be single crystal silicon, polysilicon, or amorphous silicon. By using this polishing agent, polishing of polysilicon and amorphous silicon, which have been relatively easily polished in the past, is suppressed. With this polishing agent, for example, even if the silicon surface is a patterned wafer of polysilicon or amorphous silicon, the amount of polishing of the silicon surface can be suppressed to 10 Å or less.

[0057] The silicon dioxide film on the STI substrate may be a so-called PE-TEOS film formed by plasma CVD using tetraethoxysilane (TEOS) as a raw material. The silicon dioxide film may be a so-called HDP film formed by high-density plasma CVD. In addition, HARP films and FCVD films formed by other CVD methods, and SOD films formed by spin coating may also be used. The silicon nitride film may be a film formed by low-pressure CVD or plasma CVD using silane or dichlorosilane and ammonia as raw materials, or a film formed by ALD.

[0058] A known polishing apparatus can be used in the polishing method according to the embodiment of the present invention. Fig. 3 is a schematic diagram showing an example of the polishing apparatus. The polishing apparatus 20 shown in Fig. 3 includes a polishing head 22 for holding a semiconductor substrate 21 such as an STI substrate, a polishing platen 23, a polishing pad 24 attached to the surface of the polishing platen 23, and an abrasive supply pipe 26 for supplying an abrasive 25 to the polishing pad 24. The polishing apparatus 20 is configured to bring the surface to be polished of the semiconductor substrate 21 held by the polishing head 22 into contact with the polishing pad 24 while supplying the abrasive 25 from the abrasive supply pipe 26, and to perform polishing by rotating the polishing head 22 and the polishing platen 23 relative to each other.

[0059] The polishing head 22 may perform linear motion as well as rotational motion. Furthermore, the polishing platen 23 and the polishing pad 24 may be of a size equal to or smaller than that of the semiconductor substrate 21. In that case, it is preferable to relatively move the polishing head 22 and the polishing platen 23 so that the entire surface to be polished of the semiconductor substrate 21 can be polished. Furthermore, the polishing platen 23 and the polishing pad 24 do not have to perform rotational motion, and may be, for example, a belt type that moves in one direction.

[0060] There are no particular limitations on the polishing conditions of the polishing apparatus 20, but by applying a load to the polishing head 22 and pressing it against the polishing pad 24, the polishing pressure can be increased and the polishing rate can be improved. The polishing pressure is preferably about 0.5 to 50 kPa, and more preferably about 3 to 40 kPa from the viewpoints of uniformity in the polishing rate within the polished surface of the semiconductor substrate 21, flatness, and prevention of polishing defects such as scratches. The rotation speed of the polishing platen 23 and the polishing head 22 is preferably about 50 to 500 rpm. The supply amount of the abrasive 25 is appropriately adjusted depending on the composition of the abrasive, the above-mentioned polishing conditions, and the like.

[0061] The polishing pad 24 may be made of a nonwoven fabric, polyurethane foam, porous resin, non-porous resin, or the like. In order to promote the supply of the abrasive 25 to the polishing pad 24 or to allow a certain amount of the abrasive 25 to accumulate on the polishing pad 24, the surface of the polishing pad 24 may be grooved in a lattice, concentric circle, spiral, or other shape. If necessary, a pad conditioner may be brought into contact with the surface of the polishing pad 24 to condition the surface of the polishing pad 24 while polishing. EXAMPLES

[0062] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples, "%" means mass % unless otherwise specified. In addition, the property values ​​were measured and evaluated by the following methods. Examples 1 to 5 are examples, and Example 6 is a comparative example.

[0063] [pH] The pH was measured using a pH meter HM-30R manufactured by DKK-TOA Corporation.

[0064] [Polishing characteristics] The polishing characteristics were evaluated by carrying out the following polishing using a fully automatic CMP polishing device (Applied Materials, device name: Mirra). A two-layer polyurethane pad (Shore D value 65) was used as the polishing pad, and a CVD diamond pad conditioner (Kinik, product name: Pyradia 179B) was used for conditioning the polishing pad. The polishing conditions were a polishing pressure of 21 kPa, a polishing platen rotation speed of 77 rpm, and a polishing head rotation speed of 73 rpm. The supply rate of the abrasive was 200 milliliters per minute.

[0065] [Blanket membrane] In order to measure the polishing rates of polysilicon and silicon nitride films, blanket substrates with a polysilicon (poly-Si) film and a silicon nitride (LP-SiN) film formed on an 8-inch silicon wafer were prepared as the objects to be polished (workpieces to be polished).

[0066] [Si pattern film] In order to measure the polishing rate of the polysilicon film in the patterned film, a patterned wafer having a SEMATEC864, STI pattern structure, a poly-Si stop layer, and an LP-SiN film was prepared.

[0067] [Polishing speed measuring device] The thickness of the blanket substrate and the patterned substrate was measured using a film thickness meter UV-1280SE manufactured by KLA-Tencor.

[0068] [Blanket polishing speed] For blanket substrates, the polishing rates for polysilicon and silicon nitride films were calculated by determining the difference between the film thickness before polishing and the film thickness after 1 minute of polishing. The average polishing rate (Å / min) obtained from the polishing rates at 49 points on the substrate surface was used as the evaluation index for the polishing rate.

[0069] [Pattern polishing speed] As a pattern substrate, a pattern with a line portion (polysilicon) width (L) of 10 μm and a space portion (silicon nitride) width (S) of 90 μm was prepared as shown in FIG. 4(A). The line / space ratio was determined by the inventors in advance to be a ratio at which polysilicon is easily scraped off. Polishing was performed stepwise until the upper silicon nitride film was removed and the polysilicon film was exposed, and it was confirmed that the polysilicon film was exposed (FIG. 4(B)). The state in FIG. 4(B) was considered as the initial state, and polishing was performed for an additional 30 seconds (FIG. 4(C)). The polysilicon polishing rate per minute was calculated from the change in film thickness of the polysilicon film during this 30-second polishing (d).

[0070] [Example 1: Preparation of abrasive] A cerium oxide dispersion liquid (hereinafter referred to as cerium oxide dispersion liquid a) was prepared by dispersing cerium oxide particles having an average secondary particle diameter of 60 nm in pure water. Next, pure water was added to the cerium oxide dispersion a so that the cerium oxide was 0.1 mass% relative to the total amount of the polishing agent. Next, polyoxyethylene (60) distyrylphenyl ether was added so that the amount was 0.030 mass%, and poly-p-styrenesulfonic acid was added as an anionic polymer and stirred, and phosphoric acid was further added to adjust the pH to 2.5, to obtain a slurry-like polishing agent (1). Here, the poly-p-styrenesulfonic acid was adjusted so that the polishing speed for the silicon nitride film was 600±50 Å / min.

[0071] [Examples 2 to 6: Preparation of abrasives] Abrasives (2) to (6) of Examples 2 to 6 were obtained in the same manner as in Example 1, except that in Example 1, the compound (1) and the anionic polymer were changed as shown in Table 1.

[0072] The polishing properties of the polishing agents (1) to (6) obtained in the above examples were measured by the above-mentioned methods. The measurement results are shown in Table 1.

[0073] [Table 1]

[0074] As shown in Table 1, the polishing rate of the blanket film of polysilicon (Si blanket rate: R Si ) is less than 10 Å / min in all of Examples 1 to 6. However, the Si pattern rate (R SiP ) is R Si A tendency for the rate to increase was observed. When the polishing agents of Examples 1 to 5 containing compound (1) were used, the increase in the Si pattern rate was shown to be suppressed compared to the polishing agent of Example 6 containing another surfactant. In particular, it was revealed that the polishing agents of Examples 1 to 4 using a combination of an anionic polymer having a phenyl group significantly suppressed the increase in the polishing rate of polysilicon on the patterned wafer. [Industrial Applicability]

[0075] The polishing agent of the present invention suppresses the polishing rate of the silicon surface, and therefore can be suitably used to expose a patterned surface including a silicon surface on the surface of a patterned wafer having a silicon surface and a silicon oxide film or a silicon nitride film arranged in a pattern. Therefore, the cerium oxide of the present invention is suitable for planarizing an insulating film for STI in the manufacture of semiconductor devices. [Explanation of symbols]

[0076] 1...silicon substrate, 2...silicon nitride film, 3...trench, 4...silicon oxide film, 5...silicon nitride film or silicon oxide film, 20...polishing device, 21...semiconductor substrate, 22...polishing head, 23...polishing platen, 24...polishing pad, 25...polishing agent, 26...polishing agent supply piping.

Claims

1. An abrasive for polishing a silicon nitride film, comprising: A polishing agent containing an abrasive grain and a compound represented by the following formula (1), and having a pH of 2 to 5.5: R-O-(AO) ｎ -H Formula (1) provided that R is an organic group containing a conjugated system and may have a heteroatom in the carbon skeleton, and when, among the atoms constituting the carbon skeleton, the number of atoms constituting the conjugated system is C1 and the number of atoms not constituting the conjugated system is C2, C1 / (C1+C2)≧0.4; AO represents an oxyalkylene group, and a plurality of AO may be the same or different. n is an integer from 2 to 200.

2. The abrasive of claim 1 , wherein R comprises an aryl group.

3. 3. The polishing agent according to claim 2, wherein in the R--O bond of the formula (1), the atom on the R side is a carbon atom constituting the aryl group.

4. The polishing agent according to any one of claims 1 to 3, wherein R is a hydrocarbon group.

5. The polishing agent according to any one of claims 1 to 4, wherein the compound represented by formula (1) has an HLB value of 12 to 20.

6. The polishing agent according to any one of claims 1 to 5, wherein the abrasive grains are metal oxide particles.

7. The abrasive according to any one of claims 1 to 6, further comprising a polymer.

8. The abrasive of claim 7 , wherein the polymer comprises an anionic polymer.

9. The abrasive of claim 8 , wherein the anionic polymer has an aryl group.

10. The abrasive according to any one of claims 1 to 9, which is used for exposing a pattern surface including a silicon surface on a surface.

11. A polishing method in which a surface to be polished is brought into contact with a polishing pad while an abrasive is being supplied, and polishing is performed by relative movement of the two, the method comprising using the abrasive according to any one of claims 1 to 10 as the abrasive, and polishing a surface to be polished including a surface of a semiconductor substrate made of silicon oxide.

12. The polishing method according to claim 11 , wherein a pattern surface including a silicon surface is exposed on a surface of the semiconductor substrate.

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