JP6572734B2 - Abrasive, polishing method, and additive liquid for polishing - Google Patents

Description

  The present invention relates to an abrasive, a polishing method, and an additive solution for polishing, and in particular, an abrasive for chemical mechanical polishing in the manufacture of a semiconductor integrated circuit, a polishing method using the abrasive, and an abrasive The additive liquid for grinding | polishing for preparing this.

  In recent years, along with higher integration and higher functionality of semiconductor integrated circuits, development of microfabrication techniques for miniaturization and higher density of semiconductor elements has been promoted. Conventionally, in the manufacture of a semiconductor integrated circuit device (hereinafter also referred to as a semiconductor device), in order to prevent problems such as unevenness (steps) on the surface of the layer exceeding the depth of focus of lithography, a sufficient resolution cannot be obtained. An interlayer insulating film, a buried wiring, and the like are planarized by using a chemical mechanical polishing method (hereinafter referred to as CMP). As the demand for higher definition and miniaturization of elements becomes stricter, the importance of high planarization by CMP is increasing.

  In recent years, in the manufacture of semiconductor devices, a shallow trench isolation (hereinafter referred to as STI) method using a shallow trench having a small element isolation width has been introduced in order to advance further miniaturization of semiconductor elements.

  STI is a method of forming an electrically isolated element region by forming a trench (groove) in a silicon substrate and embedding an insulating film in the trench. In STI, first, as shown in FIG. 1A, after the element region of the silicon substrate 1 is masked with a silicon nitride film 2 or the like, a trench 3 is formed in the silicon substrate 1, and carbon dioxide is buried so as to fill the trench 3. An insulating film such as a silicon film 4 is deposited. Next, by CMP, the silicon dioxide film 4 on the silicon nitride film 2 that is the convex portion is polished and removed while leaving the silicon dioxide film 4 in the trench 3 that is the concave portion. Thus, an element isolation structure in which the silicon dioxide film 4 is embedded in the trench 3 is obtained as shown in FIG.

  In CMP in such STI, it is desirable that the upper surface of the silicon dioxide film 4 in the trench 3 which is a concave portion is flush with the upper surface of the silicon nitride film 2 which is a convex portion. When the level of the upper surface of the silicon dioxide film 4 and the upper surface of the silicon nitride film 2 is defined as flatness, the carbon dioxide in the recess after polishing is removed from the upper surface of the silicon nitride film 2 before polishing. A distance (hereinafter simply referred to as “distance”) along the thickness (or height) direction to the upper surface of the silicon film 4 can be used as an index representing the flatness. The shorter the distance is, the closer the top surface of the silicon dioxide film 4 and the top surface of the silicon nitride film 2 are to be flush with each other, and the surfaces are almost the same height.

  In recent CMP techniques, not only the above-described goodness (height) of flatness but also a high polishing rate for the silicon dioxide film is required from the cost aspect, and both high polishing rate and high flatness are required. .

  From such a viewpoint, a method for improving the polishing characteristics of the abrasive has been proposed. Patent Document 1 discloses a CMP polishing agent for planarizing an interlayer insulating film, an STI insulating film, etc., including cerium oxide particles, a dispersing agent, a polycarboxylic acid having a weight average molecular weight of 500 to 20,000, 1 A polishing agent containing a strong acid (sulfuric acid) having a pKa value of 3.2 or less and water having a pKa value of 3.2 or less and having a pH of 4.0 or more and 7.5 or less is disclosed.

  However, with the polishing agent disclosed in Patent Document 1, the flatness of the substrate obtained by polishing is good, but it cannot be said that the polishing rate for the silicon dioxide film is sufficiently high.

WO2006 / 035771

  The present invention has been made to solve the above-described problems. An abrasive capable of realizing a sufficiently high polishing rate for a silicon oxide film such as a silicon dioxide film while ensuring good flatness, and polishing. It aims to provide a method.

  The abrasive of the present invention comprises cerium oxide particles, a water-soluble organic polymer having a carboxylic acid group and / or a salt of carboxylic acid, a water-soluble polyamide having a tertiary amino group and / or an oxyalkylene chain in the molecule, It contains water and has a pH of 7 or less.

  In the abrasive of the present invention, the water-soluble polyamide preferably has the tertiary amino group in the main chain and / or side chain. The water-soluble polyamide preferably has the oxyalkylene chain in the main chain. The water-soluble polyamide is preferably a copolymer obtained from aminoethylpiperazine and / or modified polyalkylene glycol and lactam. The water-soluble organic polymer preferably contains polyacrylic acid and / or ammonium polyacrylate. The water-soluble organic polymer preferably has a molecular weight of 1000 to 50000.

  The water-soluble polyamide content is preferably 0.00005% by mass or more and 0.01% by mass or less. The content of the water-soluble organic polymer is preferably 0.01% by mass or more and 0.5% by mass or less. The pH is preferably 4 or more and 6.5 or less. The average secondary particle diameter of the cerium oxide particles is preferably 0.01 μm or more and 0.5 μm or less. The content of the cerium oxide particles is preferably 0.05% by mass or more and 2% by mass or less.

  In the polishing method of the present invention, the surface to be polished and the polishing pad are brought into contact with each other while supplying the polishing agent, and polishing is performed by relative movement of both. A surface to be polished including a surface made of silicon oxide is polished.

  The polishing additive liquid of the present invention is an additive liquid for preparing an abrasive by mixing with a dispersion of cerium oxide particles, and comprising a water-soluble organic polymer having a carboxylic acid group and / or a carboxylic acid salt The water-soluble polyamide having a tertiary amino group and / or oxyalkylene chain in the molecule and water, and having a pH of 7 or less.

  In the polishing additive liquid of the present invention, the water-soluble polyamide has at least one of the tertiary amino group bonded to the main chain and / or the side chain and the oxyalkylene chain bonded to the main chain. preferable. The water-soluble polyamide is preferably a copolymer obtained from aminoethylpiperazine and / or modified polyalkylene glycol and lactam. The water-soluble organic polymer preferably contains polyacrylic acid and / or ammonium polyacrylate.

In the present invention, the “surface to be polished” is a surface to be polished of an object to be polished, such as a surface. In this specification, an intermediate stage surface that appears on a semiconductor substrate in the process of manufacturing a semiconductor device is also included in the “surface to be polished”.
In the present invention, “silicon oxide” is specifically silicon dioxide, but is not limited thereto, and includes silicon oxides other than silicon dioxide.
Furthermore, “water-soluble” refers to the property of dissolving in water at room temperature.

  According to the polishing agent and polishing method of the present invention, for example, in CMP of a surface to be polished including a surface made of silicon oxide, a high polishing rate for a silicon oxide film can be achieved while maintaining sufficiently high flatness. it can.

It is sectional drawing of the semiconductor substrate which shows the method of grind | polishing by CMP in STI. It is a figure which shows an example of the grinding | polishing apparatus which can be used for the grinding | polishing method of this invention.

  Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments, and other embodiments may belong to the category of the present invention as long as they match the gist of the present invention.

<Abrasive>
The abrasive of the present invention comprises cerium oxide particles, a water-soluble organic polymer having a carboxylic acid group and / or a salt of carboxylic acid, a water-soluble polyamide having a tertiary amino group and / or an oxyalkylene chain in the molecule, It contains water and has a pH of 7 or less.

  When the polishing agent of the present invention is used for CMP of a surface to be polished including a surface made of silicon oxide, for example, a high polishing rate for the silicon oxide film can be realized while maintaining sufficiently high flatness.

  The mechanism by which the abrasive of the present invention exhibits such excellent polishing properties is not clear, but it is not clear that the water-soluble organic polymer having a carboxylic acid group and / or a salt of carboxylic acid, and a tertiary amino acid in the molecule. It is thought that it originates in including the water-soluble polyamide which has a group and / or an oxyalkylene chain. That is, the water-soluble organic polymer having a carboxylic acid group and / or a salt of carboxylic acid and a water-soluble polyamide having a tertiary amino group and / or an oxyalkylene chain in the molecule contained in the abrasive are pH 7 or less. In this region, it is considered that this is due to electrostatic adsorption on the surface of the cerium oxide particles and the surface to be polished including the silicon oxide film through the end groups of the respective molecules. As a result of optimizing the effect of such water-soluble organic polymer and water-soluble polyamide on the surface of the cerium oxide particles and the surface to be polished including the silicon oxide film, the polishing liquid It is considered that both a high polishing rate for the silicon oxide film and a high flatness can be obtained without impairing the dispersibility of the cerium oxide particles therein.

  Hereinafter, each component contained in the abrasive | polishing agent of this invention and pH of a liquid are demonstrated.

(Cerium oxide particles)
The cerium oxide particles contained in the abrasive of the present invention have a function as abrasive grains. Although the kind of cerium oxide particle is not particularly limited, for example, cerium oxide particles produced by the methods described in JP-A Nos. 11-12561 and 2001-35818 can be used. That is, a cerium hydroxide gel is prepared by adding an alkali to an aqueous solution of cerium (IV) ammonium nitrate, and the cerium oxide particles obtained by filtering, washing, and firing, or pulverizing and firing high-purity cerium carbonate, Cerium oxide particles obtained by pulverization and classification can be used. Further, as described in JP 2010-505735 A, cerium oxide particles obtained by chemically oxidizing a cerium (III) salt in a liquid can be used.

  The average particle diameter of the cerium oxide particles is preferably 0.01 μm or more and 0.5 μm or less, and more preferably 0.03 μm or more and 0.3 μm or less. When the average particle diameter exceeds 0.5 μm, there is a possibility that polishing scratches such as scratches may occur on the surface to be polished. Further, if the average particle size is less than 0.01 μm, not only the polishing rate may be lowered, but also the ratio of the surface area per unit volume is large, so that it is easily affected by the surface condition, and the pH and additives Depending on conditions such as concentration, cerium oxide particles tend to aggregate.

In addition, since the cerium oxide particles exist as aggregated particles (secondary particles) in which the primary particles are aggregated in the liquid, the preferable average particle size of the cerium oxide particles described above is expressed by the average secondary particle size. To do. That is, the average secondary particle diameter of the cerium oxide particles is preferably 0.01 μm or more and 0.5 μm or less, and more preferably 0.03 μm or more and 0.3 μm or less.
The average secondary particle size is measured using a dispersion liquid dispersed in a dispersion medium such as pure water, using a particle size distribution analyzer such as a laser diffraction / scattering type.

  The content (content ratio or concentration) of the cerium oxide particles is preferably 0.05% by mass or more and 2.0% by mass or less with respect to the total amount of the abrasive. A particularly preferable content is 0.15% by mass or more and 0.5% by mass or less. When the content of the cerium oxide particles is 0.05% by mass or more and 2.0% by mass or less, a sufficiently high polishing rate can be obtained for the silicon oxide film. Also, the viscosity of the abrasive is not too high, and the handleability is good.

  As the cerium oxide particles, particles dispersed in a medium in advance may be used. At this time, water is preferable as the medium.

(water)
The abrasive of the present invention contains water as a medium in which cerium oxide particles are dispersed and a water-soluble organic polymer and a water-soluble polyamide described later are dissolved. Although there is no particular limitation on the type of water, pure water, ultrapure water, ion-exchanged water, etc. in consideration of effects on water-soluble organic polymers and water-soluble polyamides, prevention of impurity contamination, pH, etc. Is preferably used.

(Water-soluble organic polymer)
The water-soluble organic polymer contained in the abrasive of the present invention is a polymer having at least one of a carboxylic acid group and a carboxylic acid salt. As the water-soluble organic polymer having a carboxylic acid group and / or a salt of carboxylic acid, specifically, a homopolymer of a monomer having a carboxylic acid group such as acrylic acid, methacrylic acid, maleic acid, Homopolymers in which the carboxylic acid group moiety is a salt such as an ammonium salt. Further, a copolymer of a monomer having a carboxylic acid group and a monomer having a carboxylic acid salt, a monomer having a carboxylic acid group, a monomer having a carboxylic acid salt, a derivative such as an alkyl ester of carboxylic acid, and the like These copolymers are also preferably used.

  In particular, a polymer having an acrylic acid group or a salt group thereof is preferable. Specifically, polyacrylic acid or a polymer in which at least a part of the carboxylic acid group of polyacrylic acid is substituted with ammonium carboxylate (hereinafter referred to as polyammonium acrylate) and the like can be mentioned. When the abrasive of the present invention contains an inorganic acid as a pH adjuster, ammonium polyacrylate is particularly preferable in order to adjust the pH of the abrasive to a range of 7 or less.

  The molecular weight of the water-soluble organic polymer having a carboxylic acid group and / or a salt of a carboxylic acid is preferably in the range of 1000 to 50000, particularly preferably in the range of 2000 to 30000. In addition, the content (content ratio or concentration) of the water-soluble organic polymer is preferably 0.01% by mass or more and 0.5% by mass or less with respect to the total amount of the abrasive. When the content ratio of the water-soluble organic polymer is 0.01% by mass or more and 0.5% by mass or less, the flatness in polishing the pattern substrate is good and the polishing rate sufficient for the silicon oxide film is obtained. can get.

(Water-soluble polyamide)
The water-soluble polyamide contained in the abrasive of the present invention is a polyamide having a tertiary amino group and / or oxyalkylene chain in the molecule and having water solubility.

  In the water-soluble polyamide of the present invention, water solubility is imparted by a tertiary amino group and / or an oxyalkylene chain present in the molecule. The tertiary amino group may be introduced into the main chain of the polyamide, but may be bonded to the side chain, or may be bonded to both the main chain and the side chain. The oxyalkylene chain is preferably introduced into the main chain of the polyamide.

  Examples of monomer compounds that introduce tertiary amino groups into the main chain of polyamide include aminoethylpiperazine, bisaminopropylpiperazine, and the like. Examples of the monomer compound for introducing a tertiary amino group into the side chain of polyamide include α-dimethylamino-ε-caprolactam. Hereinafter, a monomer compound that introduces a tertiary amino group into the main chain or side chain of polyamide is referred to as an amino group-introducing monomer.

  Examples of the monomer compound for introducing an oxyethylene chain into the main chain of polyamide include modified polyalkylene glycol in which both ends of polyalkylene glycol are modified with diamine or dicarboxylic acid. And as what was modified | denatured by diamine, bisaminopropyl polyethyleneglycol is mentioned. Examples of those modified with dicarboxylic acid include biscarboxypolyethylene glycol.

  When a modified polyalkylene glycol having both ends modified with a diamine is used, it is preferable to use a substantially equimolar amount of the dicarboxylic acid. Examples of the dicarboxylic acid include adipic acid, sebacic acid, dodecanedicarboxylic acid, terephthalic acid, isophthalic acid and the like. When a modified polyalkylene glycol having both ends modified with a dicarboxylic acid is used, it is preferable to use a substantially equimolar amount of the diamine. Examples of diamines include aliphatic diamines such as hexamethylene diamine, methylpentadiamine, and nonanediamine, alicyclic diamines such as p-aminocyclohexylmethane, and aromatic diamines such as metaxylylenediamine.

  The amino group-introducing monomer and the modified polyalkylene glycol can be polymerized or copolymerized alone to obtain a water-soluble polyamide, and a water-soluble polyamide obtained by copolymerization with addition of lactams is preferred. That is, a water-soluble polyamide obtained by copolymerizing at least one of the amino group-introducing monomer, the modified polyalkylene glycol, and a lactam is preferable. The amino group-introducing monomer, the modified polyalkylene glycol, and the lactam Water-soluble polyamides obtained by copolymerizing are more preferred.

Examples of the lactams include ε-caprolactam, propion lactam, heptane lactam, capryl lactam, undecane lactam, lauryl lactam and the like.
The water-soluble polyamide is preferably a copolymer obtained from aminoethylpiperazine and / or modified polyalkylene glycol and lactam.
Examples of commercially available water-soluble polyamides include water-soluble nylon (trade name “AQ nylon”) manufactured by Toray Industries, Inc.

  The content (content ratio or concentration) of the water-soluble polyamide is preferably 0.00005% by mass or more and 0.01% by mass or less with respect to the total amount of the abrasive. The content of the water-soluble polyamide is more preferably 0.0001% by mass or more and 0.005% by mass or less, and particularly preferably 0.0005% by mass or more and 0.005% by mass or less. When the content of the water-soluble polyamide is 0.00005% by mass or more and 0.01% by mass or less, a sufficiently high polishing rate can be obtained for the silicon oxide film, and the flatness in polishing the pattern substrate is also good. is there.

(PH)
The pH of the abrasive of the present invention is preferably 7 or less. When the pH of the abrasive is 7 or less, the effect of improving the polishing rate and the flatness of the silicon oxide film can be sufficiently obtained, and the dispersion stability of the cerium oxide particles that are abrasive grains is also good. . The pH of the abrasive is preferably 4 or more and 6.5 or less, more preferably 4.5 or more and 6 or less.

  The abrasive of the present invention may contain various inorganic acids or inorganic acid salts as a pH adjuster in order to adjust the pH to a predetermined value of 7 or less. Although it does not specifically limit as an inorganic acid or an inorganic acid salt, For example, nitric acid, a sulfuric acid, hydrochloric acid, phosphoric acid, those ammonium salt, potassium salt, etc. can be used. Moreover, you may add various basic compounds to the abrasive | polishing agent of this invention as a pH adjuster. The basic compound is preferably water-soluble, but is not particularly limited. Examples of basic compounds that can be used include ammonia, potassium hydroxide, quaternary ammonium hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide, and organic amines such as monoethanolamine and ethylenediamine.

  In addition to the above components, the abrasive of the present invention can contain a dispersant. A dispersing agent is contained for stably dispersing cerium oxide particles in a dispersion medium such as pure water. Examples of the dispersant include anionic, cationic, nonionic, and amphoteric surfactants and anionic, cationic, nonionic, and amphoteric polymer compounds, and one or two of these. The above can be contained. Further, the abrasive of the present invention can appropriately contain a lubricant, a viscosity imparting agent or a viscosity modifier, a preservative, and the like as necessary.

  For the convenience of storage and transportation, the abrasive of the present invention is a water-soluble organic high-molecular compound having a dispersion of cerium oxide particles (hereinafter also referred to as dispersion α) and a carboxylic acid group and / or a salt of carboxylic acid. It may be prepared separately as two solutions of an aqueous solution in which molecules and water-soluble polyamide are dissolved in water (hereinafter also referred to as aqueous solution β), and may be mixed at the time of use. This aqueous solution β is an additive solution for polishing shown below.

<Polishing additive>
The polishing additive liquid of the present invention is an additive liquid for preparing an abrasive by mixing with a dispersion of cerium oxide particles (the above-described dispersion α), and comprising a carboxylic acid group and / or a salt of a carboxylic acid. It has a water-soluble organic polymer, a water-soluble polyamide, and water, and has a pH of 7 or less. In the preparation of the abrasive, the use of this polishing additive liquid can improve the convenience of storage and transportation of the abrasive.

  In the polishing additive liquid of the present invention, each of the water-soluble organic polymer, water-soluble polyamide, water component having the carboxylic acid group and / or carboxylic acid salt, and the pH of the liquid, and the pH of the liquid are described in It is the same as what was described about each component contained and pH of a liquid.

  In the additive solution for polishing of the present invention, the content ratio (concentration) of the water-soluble organic polymer having a carboxylic acid group and / or a salt of carboxylic acid is not particularly limited. From the viewpoint of easy mixing with the particle dispersion, the content is preferably 0.002% by mass or more and 50% by mass or less with respect to the total amount of the additive liquid.

  In the polishing additive liquid of the present invention, the content (concentration) of the water-soluble polyamide is not particularly limited, but from the viewpoint of easy handling of the additive liquid and easy mixing with the dispersion liquid of cerium oxide particles. The amount is preferably 0.0001% by mass or more and 60% by mass or less based on the total amount of the additive solution.

  The polishing additive solution of the present invention preferably has a pH of 7 or less. When the polishing additive solution has a pH of 7 or less, mixing with the dispersion of cerium oxide particles is sufficient to improve the polishing rate of the silicon oxide film and improve the flatness in polishing the pattern substrate. And an abrasive with good dispersion stability of cerium oxide particles as abrasive grains. The pH of the polishing additive solution is more preferably 4 or more and 6.5 or less, and particularly preferably 4.5 or more and 6 or less.

  In the dispersion liquid of cerium oxide particles mixed with such a polishing additive liquid, the content ratio (concentration) of the cerium oxide particles in the liquid is such as dispersibility of the cerium oxide particles and ease of handling of the dispersion liquid. From a viewpoint, 0.2 mass% or more and 40 mass% or less are preferable. 1 mass% or more and 20 mass% or less are more preferable, and 5 mass% or more and 10 mass% or less are especially preferable.

  By mixing the polishing additive liquid of the present invention with a dispersion of cerium oxide particles, it is possible to realize the above-mentioned abrasive having an improved polishing rate while maintaining sufficiently high flatness with respect to the silicon oxide film. it can. In addition, in the mixing of the polishing additive liquid and the dispersion liquid of cerium oxide particles, the polishing additive liquid may be added to and mixed with the dispersion liquid of cerium oxide particles. A dispersion may be added and mixed.

  The mixing ratio of the polishing additive liquid and the dispersion liquid of the cerium oxide particles is not particularly limited. In the mixed abrasive, the content ratio (concentration) of the water-soluble organic polymer and the water-soluble polyamide is the total amount of the abrasive. On the other hand, it may be 0.01% by mass or more and 0.5% by mass or less and 0.00005% by mass or more and 0.01% by mass or less, respectively. From the viewpoint of easy mixing of the polishing additive liquid and the dispersion liquid of cerium oxide particles, it is preferable to mix them at a mass ratio of polishing additive liquid: cerium oxide particle dispersion liquid = 130: 1 to 1: 130. .

  In addition, when dividing into two liquids, the dispersion liquid of cerium oxide particles (dispersion liquid α) and the polishing additive liquid of the present invention (aqueous solution β), and mixing them to prepare an abrasive, oxidation in the dispersion liquid α Concentration of cerium particles (concentration) and each concentration of water-soluble organic polymer and water-soluble polyamide in polishing additive solution (aqueous solution β) are concentrated to 2 to 100 times the concentration when used as an abrasive. The two solutions prepared and concentrated can be mixed and then diluted to a predetermined concentration when used as an abrasive. More specifically, for example, when the concentration of cerium oxide particles in the dispersion α and the concentration of each of the water-soluble organic polymer and the water-soluble polyamide in the polishing additive liquid are both increased by 10 times, α can be mixed with 10 parts by weight, polishing additive solution at 10 parts by weight, and water at 80 parts by weight, and diluted 10 times to obtain an abrasive.

<Preparation method of abrasive>
In order to prepare the abrasive of the present invention, a water-soluble organic polymer having a carboxylic acid group and / or a carboxylic acid salt in a dispersion obtained by dispersing the cerium oxide particles in water such as pure water or ion-exchanged water. And a method in which water-soluble polyamide is added and mixed. After mixing, a uniform abrasive is obtained by stirring for a predetermined time using a stirrer or the like. Moreover, a better dispersion state can also be obtained by using an ultrasonic disperser after mixing.

  The abrasive of the present invention does not necessarily have to be supplied to the polishing site as a mixture of all components. When the polishing agent is supplied to the polishing site, the polishing component may be mixed to have a desired composition.

  For the convenience of storage and transportation, the abrasive of the present invention is prepared separately as two liquids of a dispersion liquid of cerium oxide particles (dispersion liquid α) and the above-mentioned polishing additive liquid (aqueous solution β). You may mix. When preparing an abrasive by dividing the dispersion α into an aqueous solution β and mixing them, the concentration of the water-soluble organic polymer or water-soluble polyamide in the aqueous solution β is used as described above. For example, it may be concentrated to about 10 times that of the time and diluted with water to a predetermined concentration after mixing.

<Polishing method>
A polishing method according to an embodiment of the present invention is a method in which a surface to be polished and a polishing pad of a polishing target are brought into contact with each other while supplying the above-described polishing agent, and polishing is performed by relative movement of both. Here, the surface to be polished is a surface including a surface made of silicon dioxide of a semiconductor substrate, for example. As a semiconductor substrate, the above-mentioned STI substrate is a preferred example. The polishing method of the present invention is also effective for polishing for planarizing an interlayer insulating film between multilayer wirings in the manufacture of a semiconductor device.

  Examples of the silicon dioxide film in the STI substrate include a so-called PE-TEOS film formed by plasma CVD using tetraethoxysilane (TEOS) as a raw material. In addition, as the silicon dioxide film, a so-called HDP film formed by a high-density plasma CVD method can also be given. Examples of the silicon nitride film include films formed by low-pressure CVD or plasma CVD using silane or dichlorosilane and ammonia as raw materials.

By using the abrasive of the present invention and polishing by the method described above, the flatness can be improved. The flatness is evaluated using, for example, an STI pattern wafer. The polishing of the STI pattern is desirably stopped when the silicon nitride film is exposed, and the flatness is more advantageous as the silicon nitride film of the pattern wafer is not scraped.
In the present invention, as will be described later, in the patterned wafer, the distance from the upper surface of the silicon nitride film before polishing to the upper surface of the silicon dioxide film in the concave portion after polishing was used as an index of flatness. The amount of film thickness reduction can also be used as an index of flatness.

A known polishing apparatus can be used for the polishing method of the embodiment of the present invention. FIG. 2 is a diagram showing an example of a polishing apparatus that can be used in the polishing method of the present invention.
The polishing apparatus 20 includes a polishing head 22 that holds a semiconductor substrate 21 such as an STI substrate, a polishing surface plate 23, a polishing pad 24 attached to the surface of the polishing surface plate 23, and an abrasive agent on the polishing pad 24. And an abrasive supply pipe 26 for supplying 25. While supplying the polishing agent 25 from the polishing agent supply pipe 26, the polishing surface of the semiconductor substrate 21 held by the polishing head 22 is brought into contact with the polishing pad 24, and the polishing head 22 and the polishing surface plate 23 are rotated relatively. It is configured to polish by moving. Note that the polishing apparatus used in the embodiment of the present invention is not limited to such a structure.

  The polishing head 22 may perform not only rotational movement but also linear movement. Further, the polishing surface plate 23 and the polishing pad 24 may be as large as or smaller than the semiconductor substrate 21. In that case, it is preferable that the entire surface to be polished of the semiconductor substrate 21 can be polished by relatively moving the polishing head 22 and the polishing surface plate 23. Furthermore, the polishing surface plate 23 and the polishing pad 24 do not have to perform a rotational movement, and may be, for example, a belt type that moves in one direction.

  The polishing conditions of the polishing apparatus 20 are not particularly limited, 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 polished surface of the semiconductor substrate 21 at the polishing rate, flatness, and prevention of polishing defects such as scratches. The rotation speed of the polishing surface plate 23 and the polishing head 22 is preferably about 50 to 500 rpm, but is not limited thereto. The supply amount of the abrasive 25 is appropriately adjusted depending on the composition of the abrasive and the above polishing conditions.

  As the polishing pad 24, one made of nonwoven fabric, foamed polyurethane, porous resin, non-porous resin, or the like can be used. In order to promote the supply of the polishing agent 25 to the polishing pad 24 or to collect a certain amount of the polishing agent 25 on the polishing pad 24, groove processing such as a lattice shape, a concentric circle shape, and a spiral shape on the surface of the polishing pad 24. May be applied. Further, if necessary, the pad conditioner may be brought into contact with the surface of the polishing pad 24 to perform polishing while conditioning the surface of the polishing pad 24.

  According to the polishing method of the present invention, a surface to be polished made of silicon oxide (for example, silicon dioxide) is highly polished in a CMP process such as planarization of an interlayer insulating film or STI insulating film in manufacturing a semiconductor device. In addition to being able to polish at a high speed, high flatness can be realized.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these Examples.
Examples 1 to 10, Example 12 and Example 15 are examples, and Examples 11, 13 and 14 are comparative examples. In the following examples, “%” means mass% unless otherwise specified. The characteristic values were measured and evaluated by the following methods.

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

[Average secondary particle size]
The average secondary particle size was measured using a laser scattering / diffraction particle size distribution analyzer (manufactured by Horiba, Ltd., apparatus name: LA-920).

[Polishing characteristics]
The polishing characteristics were measured and evaluated using a fully automatic CMP polishing apparatus (Applied Materials, apparatus name: Mirra). As the polishing pad, a two-layer pad (Rodel, trade name: IC-1400, K-groove) was used, and for the polishing pad conditioning, a diamond pad conditioner (3M, trade name: A165) was used. . 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 ml / min.

  In order to measure the polishing rate, a blanket substrate with a silicon dioxide film in which a silicon dioxide film is formed by plasma CVD using tetraethoxysilane as a raw material on an 8-inch silicon wafer is used as an object to be polished (object to be polished). It was.

In addition, for the evaluation of polishing flatness, a commercially available test STI pattern substrate (trade name: 864CMP000, manufactured by International SEMATECH) was used as an object to be polished.
On this pattern substrate, a concave and convex pattern simulating an STI pattern is formed on an 8-inch silicon wafer. As the pattern, the width of each part is changed in the range of 0.5 μm to 500 μm, the line & space pattern in which the concave part and the convex part are alternately formed, and the sum of the widths of the concave part and the convex part is 100 μm. Each of the stripe patterns with the width changed in the range of 10 μm to 90 μm is formed. The film thickness of the silicon nitride film formed as a polishing stopper layer on the convex portion is 90 nm, and the depth of the trench is 350 nm. The entire surface of the pattern substrate is covered with a silicon dioxide film having a thickness of 500 nm, which is formed by plasma CVD using tetraethoxysilane as a raw material.

  A KLA-Tencor film thickness meter UV-1280SE was used to measure the film thickness of the silicon dioxide film formed on the blanket substrate and pattern substrate. In the blanket substrate, the polishing rate was calculated by determining the difference between the film thickness of the silicon dioxide film before polishing and the film thickness after polishing for 1 minute. And the average value of the said polishing rate obtained from the polishing rate of 49 points | pieces in the surface of a board | substrate was calculated | required, and it was set as the polishing rate (angstrom / min) of the silicon dioxide film.

In the evaluation of the flatness of the polishing, the pattern substrate is polished until the silicon nitride film is exposed in a stripe pattern in which the sum of the width of the concave portion and the convex portion is 100 μm and the width of the convex portion is 70 μm, and further for 30 seconds. Added polishing. Then, in the patterned substrate after polishing, the distance d from the upper surface of the silicon dioxide film in the concave portion to the silicon layer in the line and space pattern in which the widths of the concave portion and the convex portion are both 50 μm, that is, the film thickness of the silicon dioxide film in the concave portion , Measured by the above method. Then, the distance d, and obtains the difference between the reference value d _0. Here, the reference value d ₀ is based on the upper surface of the silicon nitride film before polishing, and the distance from the upper surface of the silicon nitride film before polishing to the silicon layer (this distance is the film thickness of the silicon nitride film before polishing). The center point of the lower surface of the silicon nitride film, and the line perpendicular to the lower surface of the silicon nitride film intersected with the line drawn in parallel from the bottom surface of the trench. The sum (350 nm) with the distance to was used as a reference value. The difference (d ₀ −d) between the distance d calculated in this way and the reference value d ₀ is the distance from the upper surface of the silicon nitride film before polishing to the upper surface of the silicon dioxide film in the recessed portion after polishing. Was used as an index of flatness.

Example 1
AQ nylon P-95 (trade name, manufactured by Toray Industries, Inc.) (hereinafter referred to as water-soluble polyamide A) is added to pure water so that the content ratio (concentration) with respect to the total amount of the additive solution is 0.002%. Further, after adding ammonium polyacrylate having a molecular weight of 5000 to a concentration of 0.106%, nitric acid was added to adjust the pH to 5 to obtain an additive solution. A 1000 g concentration of 0.5% cerium oxide dispersion in which cerium oxide particles having an average secondary particle size of 0.10 μm are dispersed in pure water is added to 1000 g of the additive solution, and the mixture is stirred and mixed to obtain an abrasive (1) Got.
In addition, the content rate (concentration) with respect to the whole quantity of abrasive | polishing agent (1) of water-soluble polyamide A, polyacrylic acid ammonium, and a cerium oxide particle | grain becomes 0.001%, 0.0531%, and 0.25%, respectively.

Example 2
Instead of water-soluble polyamide A, AQ nylon T-70 (trade name, manufactured by Toray Industries, Inc.) (hereinafter referred to as water-soluble polyamide B) is adjusted to a concentration of 0.002% with respect to the total amount of the additive solution. In addition to pure water, an additive solution was prepared. Other than that was carried out similarly to Example 1, and obtained the abrasive | polishing agent (2).

Example 3
The concentration with respect to the total amount of the water-soluble polyamide A additive solution was 0.0002%, and the concentration with respect to the total amount of the abrasive was 0.0001%. Other than that was carried out similarly to Example 1, and obtained the abrasive | polishing agent (3).

Example 4
The concentration with respect to the total amount of the water-soluble polyamide A additive solution was 0.001%, and the concentration with respect to the total amount of the abrasive was changed to 0.0005%. Other than that was carried out similarly to Example 1, and obtained the abrasive | polishing agent (4).

Example 5
The concentration with respect to the total amount of the water-soluble polyamide A additive solution was changed to 0.004%, and the concentration with respect to the total amount of the abrasive was changed to 0.002%. Other than that was carried out similarly to Example 1, and obtained the abrasive | polishing agent (5).

Example 6
The pH of the additive solution was changed to 4.5. Other than that was carried out similarly to Example 1, and obtained the abrasive | polishing agent (6).

Example 7
Nitric acid was added to adjust the pH to 5, and then KOH was added to adjust the pH to 6. Otherwise in the same manner as in Example 1, an abrasive (7) was obtained.

Example 8
The concentration with respect to the total amount of the ammonium polyacrylate additive solution was 0.0426%, and the concentration with respect to the total amount of the abrasive was changed to 0.0213%. Otherwise in the same manner as in Example 1, an abrasive (8) was obtained.

Example 9
The concentration relative to the total amount of the ammonium polyacrylate additive solution was changed to 0.17%, and the concentration relative to the total amount of the abrasive was changed to 0.085%. Other than that was carried out similarly to Example 1, and obtained abrasive | polishing agent (9).

Example 10
Instead of ammonium polyacrylate having a molecular weight of 5000, polyacrylic acid having a molecular weight of 5000 was used. Other than that was carried out similarly to Example 1, and obtained the abrasive | polishing agent (10).

Example 11
In the preparation of the additive solution, water-soluble polyamide A was not used. That is, ammonium polyacrylate having a molecular weight of 5000 was added to pure water so that the concentration relative to the total amount of the abrasive was 0.0531% (the concentration relative to the total amount of the additive solution was 0.1062%), and then nitric acid was added to adjust the pH. Was adjusted to 5 to obtain an additive solution. Other than that was carried out similarly to Example 1, and obtained the abrasive | polishing agent (11).

Example 12
Instead of the cerium oxide dispersion in which cerium oxide particles having an average secondary particle diameter of 0.10 μm are dispersed in pure water, a cerium oxide dispersion in which cerium oxide particles having an average secondary particle diameter of 0.18 μm are dispersed in pure water It was used. Otherwise in the same manner as in Example 1, an abrasive (12) was obtained.

Example 13
In the preparation of the additive solution, water-soluble polyamide A was not used. That is, ammonium polyacrylate having a molecular weight of 5000 was added to pure water so that the concentration relative to the total amount of the abrasive was 0.0531% (the concentration relative to the total amount of the additive solution was 0.1062%), and then nitric acid was added to adjust the pH. Was adjusted to 5 to obtain an additive solution. Otherwise in the same manner as in Example 12, an abrasive (13) was obtained.

Example 14
AQ nylon P-95 (water-soluble polyamide A) is added to pure water so that the content ratio (concentration) with respect to the total amount of the additive solution is 0.002%, and nitric acid is added to adjust the pH to 5, and the additive solution is added. Obtained. 1000 g of this additive solution is added with 1000 g of 0.5% cerium oxide dispersion in which cerium oxide particles having an average secondary particle size of 0.10 μm are dispersed in pure water, and the mixture is stirred and mixed to obtain an abrasive (14). Got.
The content ratio (concentration) of the water-soluble polyamide A and the cerium oxide particles with respect to the total amount of the abrasive (14) is 0.001% and 0.25%, respectively.

Example 15
Instead of water-soluble polyamide A, AQ nylon P-70 (trade name, manufactured by Toray Industries, Inc.) (hereinafter referred to as water-soluble polyamide C) is adjusted to a concentration of 0.002% with respect to the total amount of the additive solution. In addition to pure water, an additive solution was prepared. Otherwise in the same manner as in Example 1, an abrasive (15) was obtained.

The compositions and pH of the abrasives (1) to (15) thus obtained in Examples 1 to 15 are shown in Table 1.
Next, the polishing properties (polishing rate of silicon dioxide film, flatness of polishing) of the abrasives (1) to (15) obtained in Examples 1 to 15 were measured by the above-described methods. The measurement results are shown in Table 2 and Table 3. Here, polishing characteristics when polishing agents (1) to (11), (14) and (15) containing cerium oxide particles having an average secondary particle diameter of 0.10 μm were used (polishing of silicon dioxide film) Table 2 shows the polishing characteristics when the polishing agents (12) to (13) containing cerium oxide particles having an average secondary particle size of 0.18 μm are used (the speed and polishing flatness). Table 3 shows the polishing rate and flatness of polishing).

  From Tables 1 and 2, cerium oxide particles having an average secondary particle size of 0.10 μm, polyacrylic acid or a salt thereof, a water-soluble polyamide having a tertiary amino group and / or oxyalkylene chain in the molecule, and water The flatness of the patterned substrate after polishing is obtained by polishing using the polishing agents (1) to (10) and (15) of Examples 1 to 10 and Example 15 having a pH of 7 or less. It can be seen that it is sufficiently good and a high polishing rate for the silicon dioxide film can be obtained.

On the other hand, when the polishing agent (11) of Example 11 containing cerium oxide particles having an average secondary particle size of 0.10 μm and polyacrylate and no water-soluble polyamide was used, Compared to 10, not only the polishing rate for the silicon dioxide film is decreased, but also the flatness of the pattern substrate is deteriorated.
Moreover, when the abrasive | polishing agent (14) of Example 14 which contains cerium oxide particle | grains with an average secondary particle diameter of 0.10 micrometer and water-soluble polyamide and does not contain polyacrylate is used, it compares with Examples 1-10. Thus, it can be seen that the polishing rate for the silicon dioxide film is high, but the flatness of the pattern substrate is very poor.

  From Tables 1 and 3, cerium oxide particles having an average secondary particle diameter of 0.18 μm, polyacrylate, a water-soluble polyamide having a tertiary amino group and / or oxyalkylene chain in the molecule, water By performing polishing using the polishing agent (12) of Example 12 having a pH of 7 or less, the flatness of the patterned substrate after polishing is sufficiently good and a high polishing rate for the silicon dioxide film It can be seen that

  On the other hand, when the polishing agent (13) of Example 13 containing cerium oxide particles having an average secondary particle size of 0.18 μm, polyacrylate and no water-soluble polyamide was used, In comparison, it can be seen that not only the polishing rate for the silicon dioxide film decreases, but also the flatness of the pattern substrate deteriorates.

  According to the present invention, for example, in CMP of a surface to be polished including a surface made of silicon oxide, the polishing rate for the silicon oxide film can be improved while maintaining the flatness sufficiently high. Therefore, the abrasive | polishing agent and polishing method of this invention are suitable for planarization of the insulating film for STI in semiconductor device manufacture.

  DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Silicon nitride film, 3 ... Trench, 4 ... Silicon oxide film, 20 ... Polishing apparatus, 21 ... Semiconductor substrate, 22 ... Polishing head, 23 ... Polishing surface plate, 24 ... Polishing pad, 25 ... Polishing Agent, 26 ... abrasive supply pipe.

Claims (11)

It contains cerium oxide particles, a water-soluble organic polymer having a carboxylic acid group and / or a salt of carboxylic acid, a water-soluble polyamide having a tertiary amino group and / or oxyalkylene chain in the molecule, water, and pH Ri der but 7 or less, the water-soluble polyamide, polishing agent characterized and aminoethylpiperazine and / or modified polyalkylene glycols, Ru copolymer der obtained from a lactam, the. The abrasive according to claim 1, wherein the water-soluble organic polymer contains polyacrylic acid and / or ammonium polyacrylate. The abrasive according to claim 1 or 2, wherein the water-soluble organic polymer has a molecular weight of 1000 to 50000. The abrasive according to any one of claims 1 to 3 , wherein a content of the water-soluble polyamide is 0.00005 mass% or more and 0.01 mass% or less. The abrasive according to any one of claims 1 to 4 , wherein the content of the water-soluble organic polymer is 0.01% by mass or more and 0.5% by mass or less. The abrasive according to any one of claims 1 to 5 , wherein the pH is 4 or more and 6.5 or less. The abrasive | polishing agent of any one of Claims 1-6 whose average secondary particle diameter of the said cerium oxide particle is 0.01 micrometer or more and 0.5 micrometer or less. The abrasive according to any one of claims 1 to 7 , wherein a content of the cerium oxide particles is 0.05% by mass or more and 2% by mass or less. In a polishing method in which a surface to be polished and a polishing pad are brought into contact with each other while supplying an abrasive, and polishing is performed by relative movement between the two, the abrasive according to any one of claims 1 to 8 is used as the abrasive. A polishing method comprising polishing a surface to be polished including a surface made of silicon oxide of a semiconductor substrate. An additive solution for preparing an abrasive by mixing with a dispersion of cerium oxide particles,
A water-soluble organic polymer having a carboxylic acid group and / or a salt of carboxylic acid, a water-soluble polyamide having a tertiary amino group and / or oxyalkylene chain in the molecule, and water, and having a pH of 7 or less Ri, wherein said water-soluble polyamide, and aminoethylpiperazine and / or modified polyalkylene glycols, Ru copolymer der obtained from a lactam, the polishing additive liquid, characterized in that. The polishing additive liquid according to claim 10, wherein the water-soluble organic polymer contains polyacrylic acid and / or ammonium polyacrylate.

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