Post-CMP cleaning composition and post-CMP cleaning method

Abstract

This invention provides a post-CMP cleaning composition and a post-CMP cleaning method that can more efficiently reduce cerium residue on the surface of polished objects. [Solution] A post-CMP cleaning composition used for cleaning polished objects that have been chemically and mechanically polished (CMP) with an abrasive composition containing a cerium compound as an abrasive particle, the post-CMP cleaning composition contains silica and a water-soluble polymer. The silica concentration is 0.5% by mass or more and 10% by mass or less.

Description

[Technical Field]

[0001] The present invention relates to a post-CMP cleaning composition and a post-CMP cleaning method. [Background technology]

[0002] In recent years, with the increasing use of multilayer wiring on semiconductor substrate surfaces, chemical mechanical polishing (CMP) technology has been utilized in the manufacturing of devices to flatten semiconductor substrates by polishing them. CMP is a method of flattening the surface of a workpiece (object to be polished), such as a semiconductor substrate, using a polishing composition (slurry) containing abrasive particles such as silica, alumina, and ceria, as well as corrosion inhibitors and surfactants. The workpieces to be polished include wiring, plugs, and other components made of silicon, polysilicon, silicon oxide films, silicon nitrides, and metals.

[0003] When polishing silicon dioxide films (hereinafter referred to as TEOS films) formed using tetraethoxysilane (Si(OC2H5)4), cerium compounds such as ceria (CeO2) are used as abrasive grains. This is because when cerium (Ce) in the cerium compound forms a bond with silicon dioxide in the TEOS film, the silicon-oxygen bond in the silicon dioxide weakens, making polishing easier.

[0004] On the other hand, when a TEOS film is polished with a polishing composition containing cerium compounds as abrasive particles, it is known that cerium tends to remain on the semiconductor substrate surface after polishing. Impurities such as cerium remaining on the semiconductor substrate surface can adversely affect the electrical properties of the semiconductor and may reduce the reliability of the device. Therefore, it is desirable to introduce a cleaning process after the CMP process to remove impurities from the semiconductor substrate surface. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2018 / 168207 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, as mentioned above, the residual cerium is bound to silicon dioxide in the TEOS film, making it difficult to remove the cerium-containing residue by normal washing processes. Therefore, Patent Document 1 describes a method for reducing the cerium-containing residue after the CMP process, using a carboxyl group-containing (co)polymer, SO X Or NO Y A surface treatment composition has been proposed that comprises a substructure compound and a dispersion medium, and has a pH of 1 to 8.

[0007] In addition, with the increasing miniaturization of semiconductor substrate surfaces in recent years, the impact of impurities remaining on the semiconductor substrates has become even greater. Therefore, there is a need for cleaning compositions and cleaning methods that can further reduce the amount of cerium remaining on the semiconductor substrate surface after CMP polishing.

[0008] The present invention has been made in view of these circumstances, and aims to provide a post-CMP cleaning composition and a post-CMP cleaning method that can more efficiently reduce cerium remaining on the surface of a polished object. [Means for solving the problem]

[0009] A post-CMP cleaning composition according to one aspect of the present invention is a post-CMP cleaning composition used for cleaning polished objects that have been chemically and mechanically polished (CMP) with an abrasive composition containing a cerium compound as abrasive particles, and contains silica and a water-soluble polymer, wherein the concentration of silica is 0.5% by mass or more and 10% by mass or less.

[0010] Furthermore, another aspect of the present invention relates to a post-CMP cleaning method which includes post-CMP cleaning of a polished object that has been subjected to CMP with an abrasive composition containing a cerium compound as abrasive particles, using the post-CMP cleaning composition according to the present invention. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a post-CMP cleaning composition and a post-CMP cleaning method that can more efficiently reduce cerium remaining on the surface of a polished object. [Modes for carrying out the invention]

[0012] One embodiment of the present invention will be described in detail. Note that the following embodiments are merely examples of the present invention, and the present invention is not limited to these embodiments. Furthermore, various modifications or improvements can be made to the following embodiments, and such modified or improved forms may also be included in the present invention.

[0013] (Post-CMP cleaning assembly) One embodiment of the present invention is a post-CMP cleaning composition used for cleaning a polished object that has been chemically and mechanically polished (CMP) with an abrasive composition containing a cerium compound as an abrasive particle, and the post-CMP cleaning composition contains silica and a water-soluble polymer. The concentration of silica is 0.5% by mass or more and 10% by mass or less.

[0014] The inventors have found that using a post-CMP cleaning composition having the above configuration, cerium remaining on the surface of a polished object can be removed more efficiently.

[0015] (Polished object to be polished) A polished object refers to an object that has been polished during the polishing process. The polishing process is a chemical mechanical polishing (CMP) process, and the polishing composition used in the CMP process contains cerium compounds as abrasive particles.

[0016] The polished object to be polished according to the present invention is preferably a polished semiconductor substrate. Here, if residues are present on the surface of the polished semiconductor substrate, it may cause a decrease in the performance of the semiconductor device. Therefore, when the polished object to be polished is a semiconductor substrate, it is necessary to remove residues as much as possible in the post-CMP cleaning of the semiconductor substrate. Since the post-CMP cleaning composition according to the present invention has the effect of efficiently removing residues containing cerium, it can be suitably used for the post-CMP cleaning of such polished semiconductor substrates.

[0017] The post-CMP cleaning composition according to the present invention can more efficiently remove cerium remaining on the surface of the polished object to be polished. When polishing a TEOS film using a polishing composition containing cerium, cerium tends to remain on the surface of the polished object to be polished. Therefore, it is preferably applied to a polished object to be polished including a TEOS film. Further, the polished object to be polished may further contain single crystal silicon, silicon compounds, carbon, metal, etc. These may be used alone or in combination of two or more.

[0018] Examples of single crystal silicon include single crystal silicon, polycrystalline silicon (polysilicon), and amorphous silicon. Examples of silicon compounds include silicon nitride (SiN), silicon oxide (SiO2), and silicon carbide (SiC). The silicon oxide film includes a silicon dioxide film derived from other sources than TEOS. The silicon compound film includes a low dielectric constant film having a relative dielectric constant of 3 or less. Further, examples of the metal include tungsten, copper, aluminum, hafnium, cobalt, nickel, titanium, tantalum, gold, silver, platinum, palladium, rhodium, ruthenium, iridium, and osmium. These metals may be contained in the form of an alloy or a metal compound.

[0019] (Residue) In this specification, the residue means foreign matter adhering to the surface of the polished object to be polished. Examples of the residue include particle residue, organic residue, and other residues.

[0020] The particle residue means a component derived from granular inorganic substances such as abrasive grains contained in the polishing composition among the foreign substances adhering to the surface of the polished object to be polished. The organic residue means a component composed of organic substances such as organic low-molecular compounds and high-molecular compounds, and organic salts among the foreign substances adhering to the surface of the polished object to be polished. The other residue means a residue composed of components other than the particle residue and the organic residue, and a mixture of the particle residue and the organic residue, etc. Usually, cerium remaining on the surface of a semiconductor substrate that has been CMP processed with a polishing composition containing a cerium compound as an abrasive grain exists as a particle residue.

[0021] Note that the particle residue, the organic residue, and the other residue are significantly different in color and shape respectively. Therefore, the determination of whether a foreign substance is a particle residue can be performed by visual observation using a scanning electron microscope (SEM) or the like, elemental analysis using an energy dispersive X-ray analysis (EDX) device attached to the scanning electron microscope, etc. Also, the measurement of the amount of particle residue can be performed using a wafer defect inspection device, a scanning electron microscope, energy dispersive X-ray analysis, or an inductively coupled plasma mass spectrometry (ICP-MS) device.

[0022] (Abrasive grain) The post-CMP cleaning composition according to an embodiment of the present invention contains silica as an abrasive grain. In this specification, silica has an action of mechanically polishing and removing the residue containing cerium adhering to the surface of the polished object to be polished. Commercially available products or synthetic products may be used as silica.

[0023] The type of silica is not particularly limited. Examples of the type of silica include colloidal silica, fumed silica, etc., but colloidal silica is preferable.

[0024] Methods for producing colloidal silica include the sodium silicate method and the sol-gel method. Colloidal silica produced by either method may be used, but from the viewpoint of reducing metal impurities, colloidal silica produced by the sol-gel method is preferred. Colloidal silica produced by the sol-gel method is preferred because it contains less metal impurities that have the property of diffusing in semiconductors and corrosive ions such as chloride ions. Colloidal silica can be produced by the sol-gel method using conventionally known methods. Specifically, colloidal silica can be obtained by using a hydrolyzable silicon compound (for example, alkoxysilane or its derivative) as a raw material and carrying out a hydrolysis-condensation reaction.

[0025] The silica may be colloidal silica with an organic acid immobilized on its surface. The colloidal silica may have an organic acid group such as a carboxyl group, sulfo group, phosphonic acid group, or aluminic acid group immobilized on its surface, but among these, colloidal silica with a sulfo group immobilized on its surface is preferred. In other words, the colloidal silica is preferably sulfonic acid-modified colloidal silica.

[0026] The method for producing colloidal silica with an organic acid immobilized on its surface is not particularly limited, and one example is a method of reacting colloidal silica with a silane coupling agent having an organic acid group at its terminal end.

[0027] As a specific example, if you want to immobilize sulfo groups on colloidal silica, you can do so by the method described in “Sulfonic acid-functionalized silica through of thiol groups”, Chem.Commun. 246-247 (2003). Specifically, by coupling a silane coupling agent having a thiol group, such as 3-mercaptopropyltrimethoxysilane, to colloidal silica and then oxidizing the thiol group with hydrogen peroxide, you can obtain colloidal silica with sulfo groups immobilized on its surface (sulfonic acid-modified colloidal silica).

[0028] If you want to immobilize a carboxyl group on colloidal silica, you can, for example, use the method described in “Novel Silane Coupling Agents Containing a Photolabile 2-Nitrobenzyl Ester for Introduction of a Carboxy Group on the Surface of Silica Gel”, Chemistry Letters, 3,228-229 (2000). Specifically, by coupling a silane coupling agent containing a photoreactive 2-nitrobenzyl ester to colloidal silica and then irradiating it with light, you can obtain colloidal silica with a carboxyl group immobilized on its surface (carboxylic acid-modified colloidal silica).

[0029] (Shape of silica) The shape of silica is not particularly limited. For example, it may be spherical or non-spherical. Specific examples of non-spherical shapes include polygonal prisms such as triangular and square prisms, cylindrical shapes, cylindrical shapes where the center of the cylinder is wider than the ends, donut shapes where the center of the disk is penetrated, plate shapes, so-called cocoon shapes with a constriction in the center, so-called aggregate spherical shapes where multiple particles are integrated, so-called konpeito shapes with multiple protrusions on the surface, rugby ball shapes, and many other shapes, and are not particularly limited.

[0030] (Zeta potential of silica) The zeta potential of silica in the post-CMP cleaning composition according to this embodiment is not particularly limited. For example, silica may have a negative zeta potential. If the zeta potential of silica is negative, silica aggregation is suppressed, so cerium-containing residues can be removed efficiently. Also, the polishing rate on the TEOS film can be kept low, making it easier to adjust the polishing time. The upper limit of the zeta potential of silica may be, for example, -10mV or less, -20mV or less, or -30mV or less. The lower limit of the zeta potential of silica may be, for example, -70mV or more, -60mV or more, or -50mV or more.

[0031] (Average primary particle size of silica) The size of the silica particles is not particularly limited. For example, the average primary particle diameter of silica may be 5 nm or larger, 8 nm or larger, or 10 nm or larger. If the average primary particle diameter of silica is 5 nm or larger, the residue adhering to the polished surface of the workpiece can be easily removed by the post-CMP cleaning composition. Alternatively, the average primary particle diameter of silica may be 200 nm or smaller, 150 nm or smaller, or 100 nm or smaller. If the average primary particle diameter of silica is 200 nm or smaller, it is easier to obtain a surface with fewer defects by polishing using the post-CMP cleaning composition. The average primary particle diameter of silica can be calculated, for example, based on the specific surface area (SA) of silica calculated by the BET method, assuming that the shape of the silica is a perfect sphere. For example, the average primary particle diameter of silica can be calculated from the specific surface area of ​​silica measured by the BET method using Micromeritex's "Flow SorbII 2300" and the true density of silica.

[0032] (Average secondary particle size of silica) The average secondary particle diameter of silica is not particularly limited. For example, the average secondary particle diameter of silica may be 10 nm or more, 30 nm or more, or 50 nm or more. As the average secondary particle diameter of silica increases, the resistance during polishing decreases, enabling stable polishing. Alternatively, the average secondary particle diameter of silica may be 300 nm or less, 200 nm or less, or 100 nm or less. As the average secondary particle diameter of silica decreases, the surface area per unit mass of silica increases. Therefore, the frequency of contact with cerium-containing residues increases, and the removal rate of cerium-containing residues improves. The average secondary particle diameter of silica can be measured by dynamic light scattering methods, such as laser diffraction scattering.

[0033] (Silica concentration) Furthermore, the silica concentration in the post-CMP cleaning composition according to this embodiment is 0.5% by mass or more and 10% by mass or less. If the silica concentration is 0.5% by mass or more, the residue containing cerium can be sufficiently removed. If the silica concentration is 10% by mass or less, not only can the cost of the post-CMP cleaning composition be reduced, but excessive polishing of the polished object on the semiconductor substrate during post-CMP cleaning can be suppressed. Furthermore, the lower limit of the silica concentration may be 1% by mass or more, 1.5% by mass or more, or 2% by mass or more. The upper limit of the silica concentration may be 8% by mass or less, 7% by mass or less, or 6% by mass or less. In other words, the silica concentration in the post-CMP cleaning composition may be 1% by mass or more and 8% by mass or less, 1.5% by mass or more and 7% by mass or less, or 2% by mass or more and 6% by mass or less.

[0034] (Water-soluble polymer) The post-CMP cleaning composition according to this embodiment contains a water-soluble polymer. The type of water-soluble polymer is not particularly limited. Examples of water-soluble polymers include anionic water-soluble polymers and nonionic water-soluble polymers. One type of water-soluble polymer may be used alone, or two or more types may be used in combination. That is, the water-soluble polymer may be at least one of anionic water-soluble polymers or nonionic water-soluble polymers.

[0035] The type of nonionic water-soluble polymer is not particularly limited, but it is preferable that the nonionic water-soluble polymer has structural units derived from monomers having vinyl groups. Examples of monomers having vinyl groups include vinyl alcohol, vinyl acetate, N-vinyl-2-pyrrolidone, N-vinylcaprolactam, N-vinylvalerolactam, N-vinyllaurolactam, N-vinylpiperidone, and acrylamide. The nonionic water-soluble polymer can be produced, for example, by polymerization through the reaction of vinyl groups of the above monomers. That is, the nonionic water-soluble polymer may be a polymer made from monomers having vinyl groups. The monomers having vinyl groups may be a single type or a combination of two or more types. When such a nonionic water-soluble polymer is included in the post-CMP cleaning composition, the residue removed by post-CMP cleaning is less likely to re-adhere to the surface of the polished object. Examples of nonionic water-soluble polymers include polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyvinylcaprolactam, polyvinylvalerolactam, polyvinyllaurolactam, polyvinylpiperidone, polyacrylamide, poly-N-vinylacetamide, and butenediol-vinyl alcohol copolymers. These nonionic water-soluble polymers may be used individually or in combination of two or more.

[0036] The type of anionic water-soluble polymer is not particularly limited, but it is preferable that the anionic water-soluble polymer has a sulfo group. When an anionic water-soluble polymer having a sulfo group is used as the water-soluble polymer, the zeta potential of silica tends to become negative. This makes it difficult for silica to aggregate, making it easier to remove residue from the surface of the polished object. Examples of anionic water-soluble polymers having a sulfo group include polyvinyl sulfonic acid, polystyrene sulfonic acid, polyallyl sulfonic acid, polymethallyl sulfonic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), polyisoprene sulfonic acid, (meth)acrylic acid-isoprene sulfonic acid copolymer, (meth)acrylic acid-[2-(meth)acrylamide-2-methylpropanesulfonic acid] copolymer, and (meth)acrylic acid-isoprene sulfonic acid-[2-(meth)acrylamide-2-methylpropanesulfonic acid] copolymer. These anionic water-soluble polymers may also exist in the form of a neutralized salt. These anionic water-soluble polymers may be used individually or in combination of two or more types.

[0037] The concentration of the water-soluble polymer in the post-CMP cleaning composition according to this embodiment is not particularly limited. Here, the concentration of the water-soluble polymer means the ratio of the sum of the content of nonionic water-soluble polymers and anionic water-soluble polymers relative to the total amount of the post-CMP cleaning composition ((content of anionic water-soluble polymers + content of nonionic water-soluble polymers) / total amount of post-CMP cleaning composition).

[0038] The lower limit of the concentration of the water-soluble polymer in the post-CMP cleaning composition may be 0.01% by mass or more, 0.02% by mass or more, or 0.03% by mass or more. If the concentration of the water-soluble polymer is 0.01% by mass or more, residue on the surface of the polished object can be removed more efficiently. Furthermore, the upper limit of the concentration of the water-soluble polymer in the post-CMP cleaning composition may be 1% by mass or less, 0.5% by mass or less, 0.1% by mass or less, or 0.08% by mass or less. If the concentration of the water-soluble polymer is 1% by mass or less, not only can the cost of the post-CMP cleaning composition be reduced, but deterioration of the dispersibility of abrasive grains can also be suppressed.

[0039] The weight-average molecular weight (Mw) of the water-soluble polymer in the post-CMP cleaning composition according to this embodiment is not particularly limited. The lower limit of the weight-average molecular weight of the water-soluble polymer may be, for example, 1,000 or more, 1,500 or more, or 2,000 or more. The upper limit of the weight-average molecular weight of the water-soluble polymer may be, for example, 1,500,000 or less, 1,300,000 or less, or 1,000,000 or less. The weight-average molecular weight of the water-soluble polymer can be measured as a value converted to polyethylene glycol using gel permeation chromatography (GPC).

[0040] (Liquid medium) The post-CMP cleaning composition according to this embodiment may contain a liquid medium. The liquid medium functions as a dispersion medium or solvent for dispersing or dissolving each component of the post-CMP cleaning composition (silica, water-soluble polymer, and additives such as pH adjusters as needed). Examples of liquid media include water and organic solvents, and one or more may be used alone or mixed together, but it is preferable that water is included. However, from the viewpoint of preventing the inhibition of the action of each component, it is preferable to use water that contains as few impurities as possible. Specifically, pure water, ultrapure water, or distilled water obtained by removing impurity ions with an ion exchange resin and then removing foreign matter by passing it through a filter is preferred.

[0041] (pH of post-CMP washing assembly) The pH of the post-CMP cleaning composition according to this embodiment may be 7 or less, or less than 5. If the pH of the post-CMP cleaning composition is 7 or less, the zeta potential of silica tends to become negative. This suppresses silica aggregation, so that residues containing cerium can be efficiently removed. The pH of the post-CMP cleaning composition according to this embodiment may be 1 or more, 2 or more, or 3 or more. If the pH of the post-CMP cleaning composition is 1 or more, not only will consumable parts such as polishing equipment and polishing pads that come into contact with the equipment be less prone to deterioration, but the generation of new residues due to deterioration of equipment and parts can also be suppressed. The pH of the post-CMP cleaning composition can be measured by the method described in the examples.

[0042] The post-CMP cleaning composition according to this embodiment may further contain a pH adjuster to adjust the pH to the above-mentioned range. The pH adjuster may be an acid, a base, or both, or an inorganic compound, an organic compound, or both.

[0043] Acids used as pH adjusters include, for example, inorganic acids and organic acids. Examples of inorganic acids include sulfuric acid, nitric acid, boric acid, carbonic acid, hypophosphorous acid, phosphorous acid, and phosphoric acid. Examples of organic acids include carboxylic acids and organic sulfuric acids. Specific examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid, n-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, and lactic acid. Furthermore, examples of organic sulfuric acids include methanesulfonic acid, ethanesulfonic acid, and isethionic acid. These acids may be used individually or in combination of two or more.

[0044] Examples of bases used as pH adjusters include alkali metal hydroxides or their salts, alkaline earth metal hydroxides or their salts, quaternary ammonium hydroxides or their salts, ammonia, and amines. Examples of alkali metals include potassium and sodium. Examples of alkaline earth metals include calcium and strontium. Examples of salts include carbonates, bicarbonates, sulfates, and acetates. Examples of quaternary ammonium include tetramethylammonium, tetraethylammonium, and tetrabutylammonium.

[0045] Examples of quaternary ammonium hydroxide compounds include quaternary ammonium hydroxide or its salts, such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Furthermore, examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, and guanidine. These bases may be used individually or in combination of two or more.

[0046] Furthermore, a buffer-type pH adjuster, which is a mixture of an acid and a salt of the acid, may be used as a pH adjuster. Using a buffer-type pH adjuster is preferable because it can reduce pH fluctuations during post-CMP washing. Examples of combinations of an acid and a salt of the acid include combinations of acids such as citric acid, acetic acid, and lactic acid with salts such as ammonium salt, sodium salt, and potassium salt of the acid. From the viewpoint of impurities, it is preferable to use an ammonium salt as the salt. In addition, the combination of citric acid and triammonium citrate is particularly preferred because it not only reduces pH fluctuations but also has a chelating effect on cerium.

[0047] (Other additives) A post-CMP cleaning composition according to one embodiment of the present invention may further contain known additives such as surfactants, chelating agents, oxidizing agents, thickeners, dispersants, surface protectants, antifungal agents, and preservatives, to the extent that the effects of the present invention are not impaired. The content of the above additives may be appropriately set according to their purpose of addition.

[0048] <Method for producing a post-CMP cleaning composition> The method for producing a post-CMP cleaning composition according to one aspect of the present invention is not particularly limited. The post-CMP cleaning composition can be obtained, for example, by stirring and mixing silica, a water-soluble polymer, and other additives as needed in a liquid medium. The temperature when mixing each component is not particularly limited, but 10°C to 40°C is preferred, and heating may be used to increase the dissolution rate. The mixing time is also not particularly limited as long as uniform mixing is achieved.

[0049] <Post-CMP cleaning method> Another aspect of the present invention relates to a post-CMP cleaning method for cleaning a polished object which has been subjected to CMP using an abrasive composition containing a cerium compound as abrasive particles, and includes cleaning the polished object using the post-CMP cleaning composition described above.

[0050] In this specification, post-CMP cleaning refers to a method of reducing residue on the surface of a polished object after CMP has been applied, i.e., in the post-CMP stage, and is a method of cleaning in a broad sense. According to the post-CMP cleaning method of this embodiment, residue containing cerium remaining on the surface of a polished object can be effectively removed.

[0051] The post-CMP cleaning method according to this embodiment is performed by directly contacting the post-CMP cleaning composition with the surface of the polished object. The post-CMP cleaning is not particularly limited, but can be performed, for example, by a rinse polishing treatment. The rinse polishing treatment is performed to remove foreign matter, particularly particle residues containing cerium, present on the surface of the polished object, in order to obtain a clean surface.

[0052] Rinse polishing is performed on a polishing platen with polishing pads attached, with the aim of removing residue from the surface of the polished object after final polishing (finish polishing). During this process, the frictional force (physical action) from the polishing pads and the action of the post-CMP cleaning composition remove residue from the polished surface of the object. Among the residues, particle residue is easily removed by physical action. Therefore, rinse polishing can efficiently remove particle residue.

[0053] As the polishing apparatus, a general polishing apparatus can be used, which includes a holder for holding the object to be polished, a motor with adjustable rotation speed, and a polishing platen to which a polishing pad (polishing cloth) can be attached. Furthermore, either a single-sided polishing apparatus or a double-sided polishing apparatus may be used. When performing both CMP treatment and rinse polishing treatment using the same polishing apparatus, it is preferable that the polishing apparatus is equipped with a discharge nozzle for a post-CMP cleaning composition according to one aspect of the present invention, in addition to a discharge nozzle for the polishing composition.

[0054] The polishing pad can be made of any material, including general nonwoven fabrics, polyurethanes, and porous fluororesins, without any particular restrictions. Preferably, the polishing pad has grooves to allow the polishing liquid to accumulate.

[0055] The rinse polishing conditions are not particularly limited and can be appropriately set to suit the characteristics of the post-CMP cleaning composition and the polished object.

[0056] The pressure applied to the polished workpiece during rinse polishing (polishing pressure) may be between 0.5 psi (3.4 kPa) and 10 psi (68.9 kPa).

[0057] There are no particular restrictions on the polishing time during rinse polishing. Generally, the lower limit of the polishing time during rinse polishing may be 5 seconds or more, 10 seconds or more, 15 seconds or more, or 20 seconds or more. Furthermore, the upper limit of the polishing time during rinse polishing may be 180 seconds or less, 150 seconds or less, 120 seconds or less, or 100 seconds or less, from the viewpoint of efficiently removing residue.

[0058] There are no particular restrictions on the rotational speed of the polishing plate during rinse polishing. Generally, the lower limit of the polishing plate rotational speed during rinse polishing is 10 rpm (0.17 s). -1 ) or more, and 20 rpm (0.33 s -1 ) or more, and 30 rpm (0.5 s -1 It may be ) or more. Also, the upper limit of the platen rotation speed during rinse polishing is 500 rpm (8.3 s -1 ) may be less than or equal to 300 rpm (5s -1 ) may be less than or equal to 200 rpm (3.3 s -1 ) or less is acceptable.

[0059] The method of supplying the post-CMP cleaning composition in rinse polishing is not particularly limited, and a method of continuous supply using a pump or the like (flow-through) may be adopted. The supply amount of the post-CMP cleaning composition (flow rate of the post-CMP cleaning composition) is not particularly limited, as long as it is an amount that covers the entire polished workpiece, but it is generally 100 mL / min or more and 5000 mL / min or less.

[0060] Before, after, or both before performing the post-CMP cleaning method according to one aspect of the present invention, cleaning with water may be performed. Afterwards, any water droplets adhering to the surface of the polished object may be removed and dried using a spin dryer, air blower, or the like. [Examples]

[0061] The present invention will be described in more detail using the following Examples and Comparative Examples. However, the technical scope of the present invention is not limited only to the following Examples. Also, various changes or improvements can be made to the following Examples, and forms with such changes or improvements can also be included in the present invention.

[0062] <Preparation of CMP Cleaning Composition> (Example 1) Sulfonic acid-modified colloidal silica particles (average secondary particle diameter: 70 nm) as abrasive grains, polyvinyl alcohol (weight average molecular weight: 10,000) as a nonionic water-soluble polymer, sodium polystyrene sulfonate (weight average molecular weight: 200,000) as an anionic water-soluble polymer, citric acid and triammonium citrate as a pH adjuster, and water as a liquid medium were stirred and mixed to prepare the post-CMP cleaning composition of Example 1. Each component was added so that the concentration of sulfonic acid-modified colloidal silica was 0.50% by mass, the concentration of polyvinyl alcohol was 0.01% by mass, and the concentration of sodium polystyrene sulfonate was 0.032% by mass with respect to the total amount of the post-CMP cleaning composition of Example 1. Also, citric acid and triammonium citrate were added so that the pH of the post-CMP cleaning composition was 3.4. The pH of the post-CMP cleaning composition was confirmed using a pH meter (product name: LAQUA (registered trademark), manufactured by Horiba, Ltd.).

[0063] (Examples 2 to 5) Post-CMP cleaning compositions of Examples 2 to 5 were prepared in the same manner as in Example 1, except that the concentration of sulfonic acid-modified colloidal silica was changed as shown in Table 1.

[0064] (Example 6) A post-CMP cleaning composition of Example 6 was prepared in the same manner as in Example 1, except that polyvinyl alcohol was not added.

[0065] (Example 7) The post-CMP cleaning composition of Example 7 was prepared in the same manner as in Example 1, except that sodium polystyrene sulfonate was not added.

[0066] (Examples 8-10) The post-CMP cleaning compositions of Examples 8-10 were prepared in the same manner as in Example 1, except that the pH was changed as shown in Table 1.

[0067] (Example 11) The post-CMP cleaning composition of Example 11 was prepared in the same manner as in Example 1, except that silica (average secondary particle size 70 nm) cation-modified with 3-aminopropyltriethoxysilane (APTES) was used as the abrasive grain, and no anionic water-soluble polymer was added.

[0068] (Comparative Example 1) A post-CMP cleaning composition for Comparative Example 1 was prepared in the same manner as in Example 1, except that sulfonic acid-modified colloidal silica was not added.

[0069] (Comparative Example 2) A post-CMP cleaning composition for Comparative Example 2 was prepared in the same manner as in Example 1, except that polyvinyl alcohol and sodium polystyrene sulfonate were not added.

[0070] <Measuring Zeta Potential> The zeta potential of abrasive grains in the post-CMP cleaning compositions of Examples 1-11 and Comparative Examples 1 and 2 was measured using the ELS-Z2 zeta potential / grain size measurement system manufactured by Otsuka Electronics Co., Ltd. Specifically, the post-CMP cleaning compositions were subjected to the zeta potential / grain size measurement system, and measurements were performed using the laser Doppler method (electrophoretic light scattering measurement method) with a flow cell at a measurement temperature of 25°C. The obtained data was analyzed using the Smoluchowski equation to calculate the zeta potential. These results are shown in Table 1.

[0071] [Table 1]

[0072] <Preparation of polished polishing object> A polished polishing object polished with a polishing composition containing a cerium compound as an abrasive grain was prepared by the CMP process described below.

[0073] (CMP process) As polishing objects, silicon wafers with a silicon dioxide film (TEOS film), silicon wafers with a silicon nitride film (SiN film), and silicon wafers with a polysilicon film (Poly-Si film) were prepared. The silicon dioxide film was formed by physical vapor deposition (PVD), and the silicon nitride film and the polysilicon film were formed by low-pressure chemical vapor deposition (LPCVD). Also, the thickness of each film was set to 10000 Å for the silicon dioxide film, 2500 Å for the silicon nitride film, and 5000 Å for the polysilicon film.

[0074] For each of the above silicon wafers, a polishing composition containing cerium oxide as an abrasive grain (composition: 1% by mass of cerium oxide (average secondary particle diameter 200 nm) as an abrasive grain, 1% by mass of acetic acid as a pH adjuster, solvent: water) was used, and polishing was performed under the following apparatus and conditions to obtain a polished polishing object. Then, the obtained polished polishing object was removed from the polishing platen. <CMP processing apparatus and conditions> · Polishing apparatus: CMP single-sided polishing apparatus FREX300E for 300 mm, manufactured by Ebara Corporation · Polishing pad: Hard polyurethane pad IC1010, manufactured by Nitta Haas Co., Ltd. · Polishing pressure: 3.0 psi (1 psi = 6894.76 Pa) · Rotation speed of polishing platen: 83 rpm · Rotation speed of head: 77 rpm · Supply of polishing composition: Pouring · Supply amount of polishing composition: 200 mL / min · Polishing time: 5 seconds

[0075] (Rinse polishing process) The obtained polished objects were placed on a separate polishing platen within the same polishing apparatus, and rinse polishing was performed on the surface of the polished objects using the post-CMP cleaning compositions of Examples 1 to 11 and Comparative Examples 1 and 2, under the following apparatus and conditions. <Rinse polishing apparatus and conditions> • Polishing equipment: Ebara Corporation FREX300E CMP single-sided polishing machine for 300mm • Polishing pad: Foamed polyurethane pad H800, manufactured by Fuji Spinning Holdings Co., Ltd. • Polishing pressure: 2.0 psi • Polishing plate rotation speed: 83 rpm • Head rotation speed: 77 rpm • Supply of post-CMP cleaning composition: run-through • Post-CMP cleaning composition supply rate: 300 mL / min • Post-CMP cleaning time: 30 seconds

[0076] <Rating> (Measurement of rinse polishing amount) For each silicon wafer, the film thickness before and after rinse polishing was measured using an optical interferometry film thickness analyzer ASET-f5x (manufactured by KLA-Tencor Co., Ltd.). The difference in film thickness was then calculated from the obtained values ​​and used as the amount of rinse polishing. The results are shown in Table 1.

[0077] (Number of cerium residues on the surface of silicon wafers with TEOS film) First, the TEOS film on the surface of a silicon wafer coated with TEOS after rinsing and polishing was completely dissolved using 5% hydrofluoric acid. Then, the resulting TEOS film solution was subjected to inductively coupled plasma mass spectrometry (ICP-MS) using an ICP mass spectrometer SPQ9400 (manufactured by SII Nanotechnology) to measure the number of cerium atoms in the solution. The amount of cerium residue per unit area on the TEOS film was then calculated by dividing the number of cerium atoms in the solution by the wafer area. The results are shown in Table 1.

[0078] As shown in Table 1, in all of Examples 1 to 11, the amount of cerium-containing residue after the rinse polishing treatment was 10[10 10 atoms / cm 2 or less, and in Comparative Examples 1 and 2, it was found to be greater than 10[10 10 atoms / cm 2 . From this, it was found that the post-CMP cleaning compositions of Examples 1 to 11 have a higher ability to remove cerium-containing residues than the post-CMP cleaning compositions of Comparative Examples 1 and 2.

[0079] From the results of Examples 4, 6, 7, 11, Comparative Examples 1 and 2, it was found that when the post-CMP cleaning composition contains silica and either or both of a nonionic water-soluble polymer and an anionic water-soluble polymer as the water-soluble polymer, the ability to remove cerium-containing residues is improved.

[0080] This can be considered as follows. Among the residues, since particle residues are easily removed by the physical action of the frictional force by the polishing pad, it is considered that the cerium-containing residues were efficiently removed by the silica contained in the CMP cleaning composition. And it is presumed that the residues removed in this way are less likely to reattach to the TEOS film due to the action of the water-soluble polymer contained in the CMP cleaning composition. Since the post-CMP cleaning composition of Comparative Example 1 does not contain silica, it is presumed that the cerium-containing residues were not removed very much. On the other hand, in the post-CMP cleaning composition of Comparative Example 2, since it contains silica, although the residues were removed to some extent by the physical action, since it does not contain a water-soluble polymer, it is considered that the removed residues reattached to the surface of the TEOS film.

[0081] The results from Examples 7 and 11 showed that when cation-modified colloidal silica was used as the abrasive grain in the post-CMP cleaning composition, the ability to remove cerium-containing residues improved compared to when sulfonic acid-modified colloidal silica was used, but the amount of polishing on the TEOS film also increased significantly. Therefore, when using cation-modified colloidal silica as the abrasive grain, it is considered that more careful adjustment of the polishing time is necessary to achieve the desired amount of polishing during the rinse polishing process.

[0082] Furthermore, for example, the present invention can take the following configuration. [1] A post-CMP cleaning composition used for cleaning polished objects which are polished objects that have been chemically and mechanically polished (CMP) with an abrasive composition containing a cerium compound as an abrasive grain, It contains silica and a water-soluble polymer. A post-CMP cleaning composition wherein the silica concentration is 0.5% by mass or more and 10% by mass or less. [2] The post-CMP cleaning composition according to [1], wherein the silica has a negative zeta potential. [3] The post-CMP cleaning composition according to [1] or "2", wherein the silica is colloidal silica with an organic acid fixed to its surface. [4] The post-CMP cleaning composition according to [3], wherein the colloidal silica is sulfonic acid-modified colloidal silica. [5] The post-CMP cleaning composition according to any one of [1] to [4], wherein the silica concentration is 1% by mass or more and 8% by mass or less. [6] The post-CMP cleaning composition according to any one of [1] to [5], wherein the water-soluble polymer is at least one of anionic water-soluble polymers or nonionic water-soluble polymers. [7] The post-CMP cleaning composition according to [6], wherein the anionic water-soluble polymer has a sulfo group. [8] The post-CMP cleaning composition according to [6], wherein the nonionic water-soluble polymer has structural units derived from monomers having vinyl groups. [9] A post-CMP cleaning composition according to any one of items [1] to [8], wherein the pH is 7 or less.

[10] The post-CMP cleaning composition according to [9], wherein the pH is less than 5.

[11] A method for cleaning a polished object which has been subjected to CMP using an abrasive composition containing a cerium compound as an abrasive grain, A post-CMP cleaning method comprising cleaning the polished object using the post-CMP cleaning composition described in any one of items [1] to

[10] .

Claims

1. A post-CMP cleaning composition used for cleaning polished objects that have been chemically and mechanically polished (CMP) with an abrasive composition containing a cerium compound as abrasive particles, It contains silica and a water-soluble polymer. A post-CMP cleaning composition wherein the silica concentration is 0.5% by mass or more and 10% by mass or less.

2. The post-CMP cleaning composition according to claim 1, wherein the silica has a negative zeta potential.

3. The post-CMP cleaning composition according to claim 1 or claim 2, wherein the silica is colloidal silica in which an organic acid is immobilized on its surface.

4. The post-CMP cleaning composition according to claim 3, wherein the colloidal silica is sulfonic acid-modified colloidal silica.

5. The post-CMP cleaning composition according to claim 1 or claim 2, wherein the silica concentration is 1% by mass or more and 8% by mass or less.

6. The post-CMP cleaning composition according to claim 1 or claim 2, wherein the water-soluble polymer is at least one of an anionic water-soluble polymer or a nonionic water-soluble polymer.

7. The post-CMP cleaning composition according to claim 6, wherein the anionic water-soluble polymer has a sulfo group.

8. The post-CMP cleaning composition according to claim 6, wherein the nonionic water-soluble polymer has structural units derived from monomers having vinyl groups.

9. A post-CMP cleaning composition according to claim 1 or claim 2, wherein the pH is 7 or less.

10. The post-CMP cleaning composition according to claim 9, wherein the pH is less than 5.

11. A method for cleaning a polished object which has been subjected to CMP with an abrasive composition containing a cerium compound as an abrasive particle, A post-CMP cleaning method comprising cleaning the polished object using the post-CMP cleaning composition described in claim 1 or claim 2.

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