JP2017117898A - Polishing liquid for CMP and polishing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid for CMP (chemical mechanical polishing) having high step removability.SOLUTION: A polishing liquid for CMP is used in a first polishing step of a polishing method including the first polishing step of polishing an insulation material in a substrate having a silicon base material 1 provided with recesses and protrusions on the surface, a stopper film 2 placed on the protrusions of the base material, and an insulation material 3 silicon oxide film covering the base material and a stopper, and a second polishing step of exposing the stopper film by polishing a portion on the stopper film in the insulation material. The polishing liquid contains abrasive grains, a first additive, a second additive, and water, where the first additive contains a 4-pyrone compound, the second additive contains cationic polymer having a structural unit derived from a monomer containing quaternary ammonium salt.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a CMP polishing liquid and a polishing method using the same. The present invention relates to a polishing slurry for CMP used for chemical mechanical polishing (CMP) of a semiconductor material, and a polishing method using the same, in particular, for polishing silicon oxide provided on the surface of a semiconductor wafer. The present invention relates to a polishing liquid for CMP and a polishing method using the same.

  In the field of semiconductor manufacturing, along with the improvement in performance of VLSI devices, it is becoming the limit to achieve both high integration and high speed in the miniaturization technology on the extension line of the prior art. In view of this, a technology for increasing the integration in the vertical direction while miniaturizing a semiconductor element, that is, a technology for multilayering wiring has been developed.

One of the most important techniques in the process of manufacturing a device with multi-layered wiring is the CMP technique. The CMP technique is a technique in which a thin film is formed on a substrate by chemical vapor deposition (CVD) or the like to obtain a substrate, and then the surface is flattened. If the surface of the substrate is uneven, inconveniences such as inability to focus in the exposure process and insufficient formation of a fine wiring structure occur. The CMP technology is a device manufacturing process in which an element isolation region is formed by polishing a plasma oxide film (BPSG, HDP-SiO ₂ , p-TEOS, etc.), an interlayer insulating film is formed, or silicon oxide is formed. The present invention is also applied to a step of flattening a plug (for example, an Al / Cu plug) after embedding a film including the metal wiring.

  CMP is usually performed using an apparatus capable of supplying a polishing liquid onto a polishing pad. The substrate surface is polished by pressing the substrate against the polishing pad while supplying a polishing liquid between the substrate surface and the polishing pad. In the CMP technique, a high-performance polishing liquid is one of elemental techniques, and various polishing liquids have been developed so far (see, for example, Patent Document 1 below). Patent Document 1 describes a CMP polishing liquid using a 4-pyrone-based compound.

JP 2013-175731 A

  By the way, in the step of forming the element isolation region on the base material, a groove is previously provided on the surface of the base material, and a material to be polished (for example, an insulating material such as silicon oxide) is formed by CVD or the like so as to fill the groove. The Thereafter, an element isolation region is formed by planarizing the surface of the material to be polished by CMP. When a material to be polished is formed on a substrate having an element isolation structure such as a recess (groove) on the surface, irregularities corresponding to the irregularities of the element isolation structure are also generated on the surface of the material to be polished. On the surface having irregularities, the convex portions are removed preferentially, while the concave portions are removed slowly to achieve flattening.

  In order to improve the process margin and yield of semiconductor production, it is preferable to remove unnecessary portions of the material to be polished formed on the substrate as uniformly and as fast as possible on the wafer surface. For example, when shallow trench isolation (STI) is adopted in order to cope with the narrowing of the element isolation region, the step of the material to be polished (eg, insulating material such as silicon oxide) provided on the substrate and unnecessary It is required to remove the part at a high polishing rate.

  In general, the polishing process for a material to be polished (for example, an insulating material such as silicon oxide) may be divided into two stages to improve the production efficiency. In the first polishing step (rough cutting), most of the steps of the material to be polished are removed, and in the second polishing step (finishing step), the material to be polished is made to have an arbitrary thickness, and the material to be polished is polished. Finish slowly so that the surface is sufficiently flat. In some cases, the polishing liquid is changed in the first and second polishing steps, but it is also required to finish with a single polishing liquid in order to simplify productivity and equipment.

  When the CMP for the material to be polished is divided into two or more stages as described above, in the second polishing process, the dishing needs to be minimized and the surface to be polished needs to be sufficiently flattened. In one polishing process, a high level difference removal property is required. In particular, in the first polishing step, the step removal property is required in preference to the high polishing rate for the material to be polished. However, the conventional polishing liquid such as the polishing liquid for CMP disclosed in Patent Document 1 has room for improvement in step removability even if a high polishing rate for a material to be polished such as an insulating material can be obtained.

  The present invention is intended to solve the above-described problems, and an object of the present invention is to provide a polishing liquid for CMP having a high level difference removing property and a polishing method using the same.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on additives to be added to the CMP polishing liquid. The inventors prepared a number of polishing liquids using various compounds as additives. Using these polishing liquids for CMP, an insulating material having irregularities (for example, an inorganic insulating material such as silicon oxide) was polished, and the step-removability was evaluated. As a result, it has been found that the combined use of a specific 4-pyrone-based compound and a cationic polymer having a structural unit derived from a quaternary ammonium salt-containing monomer is effective in exhibiting high step removal properties. It was.

［式（１）中、Ｘ^１１、Ｘ^１２及びＸ^１３は、それぞれ独立に、水素原子又は１価の置換基である。］ The polishing slurry for CMP according to the present invention has a base material having concave and convex portions on the surface, a stopper disposed on the convex portion of the base material, and an insulating material that covers the base material and the stopper. The first polishing in a polishing method, comprising: a first polishing step for polishing the insulating material on a base; and a second polishing step for polishing a portion of the insulating material on the stopper to expose the stopper. A polishing liquid used in the process, which contains abrasive grains, a first additive, a second additive, and water, and the first additive is represented by the following general formula (1). And the second additive includes a cationic polymer having a structural unit derived from a quaternary ammonium salt-containing monomer.

[In formula (1), X ¹¹ , X ¹² and X ¹³ are each independently a hydrogen atom or a monovalent substituent. ]

  According to the polishing slurry for CMP according to the present invention, it is possible to achieve high step removal performance when an insulating material having irregularities (for example, an inorganic insulating material such as silicon oxide) is polished.

  By the way, when the polishing treatment of the insulating material having unevenness (for example, an inorganic insulating material such as silicon oxide) is divided into two stages, through the first and second polishing processes, the density dependency is generated in the process of eliminating the steps. There's a problem. The density dependency means that the flatness of the finished product is deteriorated because the step in the region where the step is rough is canceled over the step in the region where the step (step protrusion) is dense. is there. For example, as shown in FIG. 1, using abrasive grains (cerium oxide particles or the like), a substrate having a dense step A1 and a rough step A2 (reference symbol B is a base material, reference symbol C is an insulating material) When polishing a material (for example, silicon oxide), the step in the region A2 is eliminated with priority over the region A1, and thus the flatness of the finish is deteriorated.

  On the other hand, as a result of intensive studies on additives to be added to the polishing slurry for CMP, the present inventors have obtained a specific 4-pyrone compound and a quaternary ammonium salt-containing monomer as described above. It has been found that the combined use of a cationic polymer having a structural unit derived from it is effective in eliminating the dependence on density while achieving high step removal. That is, according to the polishing slurry for CMP according to the present invention, it is possible to eliminate the dependency on density while achieving high level difference removal.

  Although the factors that produce these effects are not necessarily clear, the first additive having a specific chemical structure greatly increases the interaction between the polishing liquid and the insulating material (for example, an inorganic insulating material such as silicon oxide). As a result, it is estimated that the polishing rate increases. In addition, the use of a second additive having a specific chemical structure creates a strong load dependency and improves the removal of a stepped convex portion that is heavily loaded, while the concave portion is protected by the second additive. Therefore, it is estimated that the flatness is improved. Furthermore, since the second additive acts on the insulating material (for example, an inorganic insulating material such as silicon oxide), the polishing of the dense portion of the step (step protrusion) is prioritized from the point when the step is eliminated to some extent. It is speculated that the dependence on density will be resolved.

  As described above, the polishing slurry for CMP according to the present invention can achieve high level difference removability, and thus is suitable for polishing an insulating material (for example, an inorganic insulating material such as silicon oxide) provided on a substrate having irregularities. ing. Further, the CMP polishing liquid according to the present invention has an advantage that even if it is a semiconductor material whose step removal is relatively difficult with a conventional polishing liquid, the effect can be exhibited. For example, an insulating material (for example, an inorganic insulating material such as silicon oxide) of a substrate having a concave or convex portion provided in a T shape or a lattice shape when viewed from above, such as a semiconductor substrate having a memory cell ), The effect can be exhibited.

  According to the polishing liquid containing the 4-pyrone compound represented by the formula (1), in addition to achieving a sufficiently high polishing rate for an insulating material (for example, an inorganic insulating material such as silicon oxide), Aggregation of abrasive grains can be suppressed. Although the cause of the effect is not necessarily clear, the 4-pyrone compound having the specific structure described above increases the interaction between the polishing liquid and the insulating material (for example, an inorganic insulating material such as silicon oxide). Although it is an additive to be obtained, there is no effect of weakening the repulsive force such as electrostatic repulsive force between the abrasive grains, and it is considered that aggregation of the abrasive grains can be suppressed.

  The first additive comprises 3-hydroxy-2-methyl-4-pyrone, 5-hydroxy-2- (hydroxymethyl) -4-pyrone, and 2-ethyl-3-hydroxy-4-pyrone. It is preferable to include at least one compound selected from the group.

  The second additive is vinylpyrrolidone / dimethylaminoethyl methacrylate diethyl sulfate copolymer, diallyldimethylammonium chloride homopolymer, diallyldimethylammonium chloride / acrylamide copolymer, and diallylmethylethylammonium ethyl sulfate homopolymer It is preferable to include at least one compound selected from the group consisting of polymers.

  The CMP polishing liquid according to the present invention may not contain a polymer compound having an aromatic ring and a polyoxyalkylene chain.

  The pH of the polishing slurry for CMP according to the present invention is preferably 8.0 or less, and more preferably 2.0 to 5.0.

  The CMP polishing liquid according to the present invention may further contain a pH adjusting agent.

  The content of the first additive is preferably 0.001 to 5 parts by mass with respect to 100 parts by mass of the polishing liquid. By adopting such a configuration, the effect of improving the polishing rate can be obtained more efficiently.

  The content of the second additive is preferably 0.00001 to 5 parts by mass with respect to 100 parts by mass of the polishing liquid. By adopting such a configuration, the step removal effect can be obtained more efficiently.

  The abrasive content is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the polishing liquid.

  The average particle size of the abrasive grains is preferably 50 to 500 nm. The abrasive grains preferably contain a cerium compound. The cerium compound is preferably cerium oxide. It is preferable that the abrasive grains include polycrystalline cerium oxide having a crystal grain boundary. By adopting one configuration or two or more configurations among these configurations related to the abrasive grains, the polishing rate of the insulating material (for example, an inorganic insulating material such as silicon oxide) is further improved.

  The polishing slurry for CMP according to the present invention may further contain a nonionic surfactant. By adopting such a configuration, the dispersion stability of the abrasive grains in the polishing liquid is improved.

  The CMP polishing liquid according to the present invention preferably further contains a saturated monocarboxylic acid. By adopting such a configuration, an advantage of improving the polishing rate of a flat substrate (semiconductor substrate, etc.) without reducing the polishing rate of a substrate having a concavo-convex shape (semiconductor substrate, etc.), or a wafer surface with a polishing rate The advantage of improving the in-plane uniformity, which is an index of the variation within, is obtained.

  The saturated monocarboxylic acid preferably has 2 to 6 carbon atoms. By adopting such a configuration, the effect of improving the polishing rate of the flat substrate (semiconductor substrate or the like) and the effect of improving the in-plane uniformity can be further improved.

  The saturated monocarboxylic acid is acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, hydroangelic acid, caproic acid, 2-methylpentanoic acid, 4-methylpentanoic acid, 2,3- It is preferably at least one compound selected from the group consisting of dimethylbutanoic acid, 2-ethylbutanoic acid, 2,2-dimethylbutanoic acid and 3,3-dimethylbutanoic acid.

  The content of the saturated monocarboxylic acid is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the polishing liquid. By adopting such a configuration, the effect of improving the polishing rate and the effect of improving in-plane uniformity of a flat substrate (semiconductor substrate or the like) can be obtained more efficiently.

  The present invention provides a polishing method using the polishing liquid. That is, the polishing method according to the present invention includes a base material having a concave portion and a convex portion on the surface, a stopper disposed on the convex portion of the base material, and an insulating material that covers the base material and the stopper. A polishing method comprising: a first polishing step for polishing the insulating material on a base; and a second polishing step for polishing a portion of the insulating material on the stopper to expose the stopper. In one polishing step, the insulating material is polished by the polishing pad while supplying the CMP polishing liquid according to the present invention between the insulating material and the polishing pad. According to this polishing method, a sufficiently high polishing rate for an insulating material (for example, an inorganic insulating material such as silicon oxide) can be achieved, and an insulating material having irregularities (for example, an inorganic insulating material such as silicon oxide) is polished. In some cases, high step removal can be achieved. In addition, since a high polishing rate is achieved without greatly depending on the surface shape of the substrate to be polished, this polishing method includes rough cutting of an insulating material (for example, an inorganic insulating material such as silicon oxide) and a memory cell. It is suitable for polishing a semiconductor substrate having

  The base may have a portion in which the concave portion or the convex portion is provided in a T shape or a lattice shape when viewed from above. The substrate may be a semiconductor substrate having memory cells.

  ADVANTAGE OF THE INVENTION According to this invention, when the insulating material (for example, inorganic insulating materials, such as silicon oxide) which has an unevenness | corrugation is grind | polished, the polishing liquid for CMP which can achieve high level | step difference removal property, and the grinding | polishing method using the same are provided. can do. In addition, according to the present invention, it is possible to eliminate the dependence on density while achieving high level difference removability.

  In addition, the CMP polishing liquid according to the present invention can exhibit a specific load dependency as shown in FIG. 3 by containing the second additive. By expressing the load dependency as shown in FIG. 3, when an insulating material having irregularities is polished, a low polishing rate can be exhibited in a concave portion that is difficult to apply a load, and a high polishing rate can be exhibited in a convex portion that is likely to be loaded. .

FIG. 5 is a schematic cross-sectional view for explaining a phenomenon in which a material to be polished having a region having a dense step and a region having a rough step is polished to cause a dependency on the density. It is a schematic cross-sectional view showing a process in which a silicon oxide film is polished to form a shallow trench isolation structure in a semiconductor substrate. It is a figure which shows the evaluation result of load dependence.

  Hereinafter, embodiments of the present invention will be described in detail.

<CMP polishing liquid>
The polishing slurry for CMP according to the present embodiment includes a base material having a concave portion and a convex portion on the surface, a stopper disposed on the convex portion of the base material, and an insulating material that covers the base material and the stopper. A first polishing step for polishing the insulating material in the substrate having the first polishing step, and a second polishing step for polishing a portion of the insulating material on the stopper to expose the stopper. Used in the polishing process. Further, the CMP polishing liquid according to this embodiment contains abrasive grains (polishing particles), a first additive, a second additive, and water, and the first additive is generally A 4-pyrone-based compound represented by the formula (1) is included, and the second additive includes a cationic polymer having a structural unit derived from a quaternary ammonium salt-containing monomer. According to the polishing slurry for CMP according to the present embodiment, it is possible to eliminate the dependency on the density while achieving high step removal performance with respect to an insulating material having irregularities (for example, an inorganic insulating material such as silicon oxide). Hereinafter, each component etc. which are used for preparation of polishing liquid are demonstrated.

(Abrasive grains)
The abrasive grains can include, for example, a cerium compound, alumina, silica, titania, zirconia, magnesia, mullite, silicon nitride, α-sialon, aluminum nitride, titanium nitride, silicon carbide, boron carbide, and the like. As a constituent component of these abrasive grains, one kind may be used alone, or two or more kinds may be used in combination. Among these, the addition effect of the first additive and the second additive can be exhibited more satisfactorily, and a high polishing rate and a high step for an insulating material having unevenness (for example, an inorganic insulating material such as silicon oxide). A cerium-based compound is preferable from the viewpoint of obtaining a higher degree of removability.

  A polishing liquid for CMP using abrasive grains containing a cerium-based compound has a feature that relatively few polishing scratches are generated on the surface to be polished. Conventionally, CMP polishing liquid containing silica particles as abrasive grains has been widely used from the viewpoint of easily achieving a high polishing rate for an insulating material (for example, an inorganic insulating material such as silicon oxide). However, the CMP polishing liquid using silica particles generally has a problem that polishing scratches are likely to occur on the surface to be polished. In a device having a fine pattern with a wiring width of 45 nm or later, even a fine scratch that has not been a problem may affect the reliability of the device.

  Examples of the cerium compound include cerium oxide, cerium hydroxide, ammonium cerium nitrate, cerium acetate, cerium sulfate hydrate, cerium bromate, cerium bromide, cerium chloride, cerium oxalate, cerium nitrate, and cerium carbonate. . Among these, cerium oxide is preferable. By using cerium oxide, it is possible to achieve a high polishing rate and a high level difference removability at a high level, and to obtain an excellent polished surface with few polishing flaws.

  When cerium oxide is used, the abrasive grains preferably include polycrystalline cerium oxide having a crystal grain boundary (for example, polycrystalline cerium oxide having a plurality of crystallites surrounded by the crystal grain boundary). The polycrystalline cerium oxide particles having such a structure are different from simple aggregates in which single crystal particles are aggregated, and become fine due to stress during polishing, and at the same time, have an active surface (a surface not exposed to the outside before becoming fine). Since it appears one after another, it is considered that a high polishing rate for an insulating material (for example, an inorganic insulating material such as silicon oxide) can be maintained at a high level. Such polycrystalline cerium oxide particles are described in detail in, for example, International Publication No. WO99 / 31195.

  Although there is no restriction | limiting in particular as a manufacturing method of the abrasive grain containing a cerium oxide, The method of oxidizing by liquid phase synthesis; baking or hydrogen peroxide etc. is mentioned. When obtaining abrasive grains containing polycrystalline cerium oxide having crystal grain boundaries, a method of firing a cerium source such as cerium carbonate is preferred. As for the temperature at the time of the said baking, 350-900 degreeC is preferable. When the produced cerium oxide particles are aggregated, it is preferably mechanically pulverized. The pulverization method is not particularly limited, but for example, dry pulverization using a jet mill or the like; wet pulverization using a planetary bead mill or the like is preferable. The jet mill is described in, for example, “Chemical Engineering Papers”, Vol. 6, No. 5, (1980), pages 527-532.

  The average particle size of the abrasive grains is preferably 50 nm or more, more preferably 70 nm or more, and still more preferably 80 nm or more. When the average particle size is 50 nm or more, there is a tendency that the polishing rate of an insulating material (for example, an inorganic insulating material such as silicon oxide) can be increased as compared with the case of less than 50 nm. The average particle size of the abrasive grains is preferably 500 nm or less, more preferably 300 nm or less, still more preferably 280 nm or less, particularly preferably 250 nm or less, and extremely preferably 200 nm or less. When the average particle size is 500 nm or less, there is a tendency that polishing flaws can be suppressed as compared with the case where the average particle size exceeds 500 nm. In order to control the average particle diameter of the abrasive grains, a conventionally known method can be used. Taking the cerium oxide particles as an example, control of the firing temperature, firing time, pulverization conditions, etc .; filtration, classification, etc. Application.

  The average particle diameter of the abrasive grains is the D50% particle diameter of the abrasive grains, and means the median value of the volume distribution obtained by measuring the polishing liquid sample in which the abrasive grains are dispersed with a scattering type particle size distribution meter. Specifically, it is a value measured using LA-920 (trade name) manufactured by HORIBA, Ltd. The abrasive content of the polishing liquid sample is adjusted so that the abrasive content is 0.5 parts by mass with respect to 100 parts by mass of the polishing liquid sample, and this is set in LA-920 to the center of the volume distribution. Measure the value. In addition, the degree of agglomeration of abrasive grains can also be evaluated by measuring the median diameter (cumulative median value) with LA-920. When measuring the average particle diameter of the abrasive grains in the CMP polishing liquid, the content of the abrasive grains is reduced to 0.5 parts by mass with respect to 100 parts by mass of the polishing liquid sample by concentrating or diluting the CMP polishing liquid with water. It can measure by the same method, after adjusting content of the abrasive grain of a polishing liquid sample so that it may become a mass part.

  The content of the abrasive grains (particle content) is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and further preferably 0.15 parts by mass or more with respect to 100 parts by mass of the polishing slurry for CMP. Preferably, 0.2 mass part or more is especially preferable. When the content of the abrasive grains is 0.01 parts by mass or more, a higher polishing rate tends to be achieved as compared to the case of less than 0.01 parts by mass. The content of the abrasive is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, still more preferably 3.0 parts by mass or less, and 2.0 parts by mass with respect to 100 parts by mass of the polishing slurry for CMP. The following is particularly preferable, and 1.0 part by mass or less is extremely preferable. When the content of the abrasive grains is 10 parts by mass or less, compared to a case where the content exceeds 10 parts by mass, aggregation of the abrasive grains tends to be suppressed, and a high polishing rate tends to be easily achieved.

(First additive)
A 1st additive contains 1 type (s) or 2 or more types from the 4-pyrone type compound represented by following General formula (1).

In formula (1), X ¹¹ , X ¹² and X ¹³ are each independently a hydrogen atom or a monovalent substituent. Examples of the monovalent substituent include an aldehyde group, a hydroxy group (hydroxyl group), a carboxyl group, a sulfonic acid group, a phosphoric acid group, a bromine atom, a chlorine atom, an iodine atom, a fluorine atom, a nitro group, a hydrazine group, 8 alkyl groups (which may be substituted with OH, COOH, Br, Cl, I, or NO ₂ ), C 6-12 aryl groups, C 2-8 alkenyl groups, and the like.

When the 4-pyrone compound has a monovalent substituent as X ¹¹ , X ¹² and X ¹³ , the monovalent substituent is bonded to a carbon atom adjacent to the oxy group from the viewpoint of easy synthesis. It is preferable. That is, it is preferable that at least one of X ¹¹ and X ¹² is a monovalent substituent. Furthermore, easy in view to obtain the effect of improving abrasive grains of the polishing ^ability, it is preferable that at least two are hydrogen atom of X ^{11, X 12} and ^{X 13,} among the X ^{11, X 12} and ^{X 13} 2 More preferably, one is a hydrogen atom.

  The 4-pyrone compound has a structure in which a hydroxy group is bonded to at least a carbon atom adjacent to a carbon atom of a carbonyl group. Here, the “4-pyrone compound” includes an oxy group and a carbonyl group, and has a 6-membered ring (γ-pyrone ring) structure in which the carbonyl group is located at the 4-position with respect to the oxy group. It is a heterocyclic compound. In the 4-pyrone compound of this embodiment, a hydroxy group is bonded to a carbon atom adjacent to the carbonyl group in the γ-pyrone ring, and a substituent other than a hydrogen atom is attached to the other carbon atom. May be substituted.

  As such a 4-pyrone-based compound, 3-hydroxy-2-methyl-4-pyrone (also known as 3-hydroxy-2-methyl-) is preferable from the viewpoint of more suitably obtaining the effect of achieving high step removal performance. 4H-pyran-4-one, maltol), 5-hydroxy-2- (hydroxymethyl) -4-pyrone (also known as 5-hydroxy-2- (hydroxymethyl) -4H-pyran-4-one, kojic acid) And at least one compound selected from the group consisting of 2-ethyl-3-hydroxy-4-pyrone (also known as 2-ethyl-3-hydroxy-4H-pyran-4-one) is preferable.

  As a 1st additive, 1 type may be used independently and 2 or more types may be used together. A high polishing rate can also be obtained by using a combination of two or more first additives.

  The first additive is preferably water-soluble. By using a compound having a high solubility in water, a desired amount of the first additive can be dissolved well in the polishing slurry for CMP, and an effect of improving the polishing rate and agglomeration of abrasive grains can be achieved. There is a tendency that the suppression effect can be achieved to a higher level. The solubility of the first additive in 100 g of water at room temperature (25 ° C.) is preferably 0.001 g or more, more preferably 0.005 g or more, still more preferably 0.01 g or more, and particularly preferably 0.05 g or more. The upper limit of solubility is not particularly limited.

  The content of the first additive is preferably 0.001 part by mass or more, more preferably 0.003 part by mass or more, and further preferably 0.005 part by mass or more with respect to 100 parts by mass of the CMP polishing liquid. When the content of the first additive is 0.001 part by mass or more, a stable polishing rate tends to be achieved as compared with the case of less than 0.001 part by mass. The content of the first additive is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, and 0.5 parts by mass or less with respect to 100 parts by mass of the polishing slurry for CMP. Is particularly preferred. When the content of the first additive is 5 parts by mass or less, compared to a case where the content exceeds 5 parts by mass, aggregation of abrasive grains tends to be suppressed and a high polishing rate tends to be easily achieved.

(Second additive)
The polishing slurry for CMP according to this embodiment contains a cationic polymer (excluding a compound corresponding to the first additive) having a structural unit derived from a quaternary ammonium salt-containing monomer as the second additive. ing. As a 2nd additive, 1 type may be used independently and 2 or more types may be used together.

  The cationic polymer having a structural unit derived from a quaternary ammonium salt-containing monomer may be a homopolymer of a quaternary ammonium salt-containing monomer, and contains a quaternary ammonium salt-containing monomer and the quaternary ammonium salt-containing monomer. It may be a copolymer of a monomer and a copolymerizable monomer. Examples of the quaternary ammonium salt-containing monomer include quaternary ammonium salt-containing (meth) acrylate monomers such as dimethylaminoethyl (meth) acrylate diethyl sulfate, diallyldimethylammonium chloride, diallylmethylethylammonium ethyl sulfate, and the like. . The monomer copolymerizable with the quaternary ammonium salt-containing monomer is not particularly limited, and examples thereof include vinyl pyrrolidone and acrylamide. Cationic polymers having structural units derived from quaternary ammonium salt-containing monomers include vinylpyrrolidone / dimethylaminoethyl (meth) acrylate diethylsulfate copolymer, diallyldimethylammonium chloride homopolymer, diallyldimethylammonium chloride / acrylamide. Examples thereof include a copolymer and diallylmethylethylammonium ethyl sulfate homopolymer.

  As a second additive, vinylpyrrolidone-dimethylaminoethyl methacrylate diethyl sulfate copolymer and diallyldimethyl are used from the viewpoint of more suitably obtaining the effect of eliminating the dependence on density while achieving high step removal performance. At least one selected from the group consisting of ammonium chloride homopolymers is preferred.

  The weight average molecular weight of the second additive is preferably 100,000 or more, preferably 200,000 or more from the viewpoint that the functional group in the second additive easily reacts with the insulating material (for example, an inorganic insulating material such as silicon oxide). Is more preferable. The upper limit of the weight average molecular weight may be 1 million, for example.

In addition, the weight average molecular weight of a 2nd additive can be measured on condition of the following by the gel permeation chromatography method (GPC) using the analytical curve of a standard polystyrene, for example.
Equipment used: Hitachi L-6000 (manufactured by Hitachi, Ltd.)
Column: Gel pack GL-R420 + Gel pack GL-R430 + Gel pack GL-R440 [trade name, manufactured by Hitachi Chemical Co., Ltd., total of 3]
Eluent: Tetrahydrofuran Measurement temperature: 40 ° C
Flow rate: 1.75 mL / min
Detector: L-3300RI [manufactured by Hitachi, Ltd.]

  The second additive is preferably water-soluble. By using a compound with high solubility in water, the desired amount of the second additive can be well dissolved in the polishing liquid for CMP, eliminating the dependency on density while achieving high step removal. This effect can be achieved at a higher level. The solubility of the second additive in 100 g of water at room temperature (25 ° C.) is preferably 0.005 g or more, and more preferably 0.02 g or more. The upper limit of solubility is not particularly limited.

  The content of the second additive is preferably 0.00001 parts by mass or more, more preferably 0.00005 parts by mass or more, and further preferably 0.0001 parts by mass or more with respect to 100 parts by mass of the polishing slurry for CMP. When the content of the second additive is 0.00001 part by mass or more, the effect of eliminating the dependency on the density is stabilized while achieving high step removability as compared with the case of less than 0.00001 part by mass. Tend to be easily obtained. The content of the second additive is preferably 5 parts by mass or less, more preferably 1 part by mass or less, and still more preferably 0.1 part by mass or less with respect to 100 parts by mass of the CMP polishing liquid. When the content of the second additive is 5 parts by mass or less, it is easier to suppress agglomeration of the abrasive grains than in the case where the content exceeds 5 parts by mass, and the effect of achieving high step removal is stably obtained. Tend to be. Further, by adopting the upper limit value, it is possible to prevent the CMP polishing liquid from being deteriorated and store it in a more stable state. The content of the second additive is preferably 0.00001 to 5 parts by mass with respect to 100 parts by mass of the polishing slurry for CMP, from the viewpoint of more efficiently obtaining the effect of removing the step. 5 mass parts is more preferable, 0.00005-1 mass part is still more preferable, and 0.0001-0.1 mass part is especially preferable. The content of the second additive can be appropriately adjusted according to the type of the first additive or the type of the second additive.

(water)
The water contained in the CMP polishing liquid according to the present embodiment is not particularly limited, but deionized water, ion-exchanged water, and ultrapure water are preferable. In addition, you may use polar solvents, such as ethanol and acetone, together with water as needed.

(Third additive)
The CMP polishing liquid according to this embodiment preferably contains a saturated monocarboxylic acid as the third additive. Thereby, there exists a tendency which can improve the grinding | polishing speed | rate of a wafer (blanket wafer) without an unevenness | corrugation. In general, in polishing a wafer having irregularities, the surface to be polished tends to approach the state of a blanket wafer as the polishing progresses because the convex portions are polished preferentially. Therefore, a polishing liquid that is also excellent in the blanket wafer polishing rate is preferable in that a good polishing rate can be obtained throughout the entire process.

  From the above viewpoint, the saturated monocarboxylic acid preferably has 2 to 6 carbon atoms. Saturated monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, hydroangelic acid, caproic acid, 2-methylpentanoic acid, 4-methylpentanoic acid, 2,3- Preference is given to at least one compound selected from the group consisting of dimethylbutanoic acid, 2-ethylbutanoic acid, 2,2-dimethylbutanoic acid and 3,3-dimethylbutanoic acid. As the saturated monocarboxylic acid, one of these compounds may be used alone, or two or more may be used in combination.

  When a saturated monocarboxylic acid is used as the third additive, the content of the third additive is preferably 0.01 parts by mass or more with respect to 100 parts by mass of the CMP polishing liquid, and 0.05 parts by mass. The above is more preferable, 0.075 parts by mass or more is further preferable, and 0.09 parts by mass or more is particularly preferable. When the content of the third additive is 0.01 parts by mass or more, a stable polishing rate and good in-plane uniformity tend to be achieved. The content of the third additive is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3 parts by mass or less, and particularly preferably 2 parts by mass or less, with respect to 100 parts by mass of the polishing slurry for CMP. The amount is preferably 1 part by mass or less. When the content of the third additive is 10 parts by mass or less, compared to the case where the content exceeds 10 parts by mass, the agglomeration of the abrasive grains is easily suppressed, and a stable polishing rate and good in-plane uniformity are achieved. There is a tendency to be easily done.

(Other ingredients)
The CMP polishing liquid according to this embodiment corresponds to a surfactant (first additive or second additive) from the viewpoint of improving the dispersion stability of the abrasive grains and / or the flatness of the surface to be polished. Excluding compounds). Examples of the surfactant include ionic surfactants and nonionic surfactants, and nonionic surfactants are preferred. As the surfactant, one type may be used alone, or two or more types may be used in combination.

  Nonionic surfactants include polyoxypropylene polyoxyethylene alkyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene polyoxypropylene ether derivatives, polyoxypropylene glyceryl ether, polyethylene glycol oxyethylene Ether type surfactants such as adducts, oxyethylene adducts of methoxypolyethylene glycol, oxyethylene adducts of acetylenic diols; ester type surfactants such as sorbitan fatty acid esters and glycerol borate fatty acid esters; polyoxyethylene alkylamines Amino ether type surfactants such as polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerol borate fatty acid ester Ether ester type surfactants such as polyoxyethylene alkyl esters; fatty acid alkanolamides, alkanolamide type surfactants such as polyoxyethylene fatty acid alkanolamides; oxyethylene adducts of acetylenic diols; polyvinylpyrrolidone; polyacrylamide; Polydimethylacrylamide; and polyvinyl alcohol. As a nonionic surfactant, 1 type may be used independently and 2 or more types may be used together. The CMP polishing liquid according to the present embodiment may not contain a polymer compound having an aromatic ring and a polyoxyalkylene chain (polyoxyethylene styrenated phenyl ether, polyoxyethylene alkylphenyl ether, etc.).

  The CMP polishing liquid according to this embodiment may contain other components in addition to the surfactant in accordance with desired characteristics. Examples of such components include pH adjusters as described later, pH buffering agents for suppressing fluctuations in pH, aminocarboxylic acids (excluding compounds corresponding to the third additive), cyclic monocarboxylic acids, and the like. It is done. The content of these components is preferably in a range that does not excessively reduce the effect of the polishing liquid.

(PH)
The pH of the CMP polishing liquid according to the present embodiment tends to improve wettability between the polishing liquid and an insulating material (for example, an inorganic insulating material such as silicon oxide), and tends to suppress agglomeration of abrasive grains. In view of the above, 8.0 or less is preferable, less than 8.0 is more preferable, 7.0 or less is more preferable, 6.0 or less is particularly preferable, and 5.0 or less is extremely preferable. When the pH is 8.0 or less, compared to a case where the pH exceeds 8.0, it is easy to suppress the aggregation of abrasive grains and the like, and the effect of adding the additive tends to be easily obtained. The pH of the polishing liquid is preferably 1.5 or more, and more preferably 2.0 or more. When the pH is 1.5 or more, the absolute value of the zeta potential of an insulating material (for example, an inorganic insulating material such as silicon oxide) tends to be large as compared with a case of less than 1.5. . The pH of the CMP polishing liquid according to this embodiment is 2.0 to 5.0 from the viewpoint of improving the wettability between the polishing liquid and an insulating material (for example, an inorganic insulating material such as silicon oxide). preferable. The pH is defined as the pH at a liquid temperature of 25 ° C.

  The pH of the polishing slurry for CMP according to this embodiment can be measured with a pH meter (for example, model number PHL-40 manufactured by Electrochemical Instrument Co., Ltd.). For example, using a phthalate pH buffer (pH 4.01), a neutral phosphate pH buffer (pH 6.86), and a borate pH buffer (pH 9.18) as standard buffers, After three-point calibration, the electrode of the pH meter is put into the polishing liquid, and the value after 3 minutes has passed and stabilized is measured. At this time, both the standard buffer solution and the polishing solution are set to 25 ° C.

It is considered that the following two effects can be obtained by adjusting the pH of the CMP polishing liquid within the range of 1.5 to 8.0.
(1) Proton or hydroxy anion acts on a compound blended as an additive to change the chemical form of the compound, and wettability to an insulating material (for example, silicon oxide) and / or a stopper (for example, silicon nitride) on the substrate surface. And the affinity is improved.
(2) When the abrasive grains contain cerium oxide, when polishing silicon oxide, the contact efficiency between the abrasive grains and silicon oxide is improved, and a higher polishing rate is achieved. This is thought to be because the sign of the zeta potential of cerium oxide is positive while the sign of the zeta potential of silicon oxide is negative, and an electrostatic attractive force acts between them.

  The pH of the CMP polishing liquid can vary depending on the type of compound used as an additive. Therefore, the CMP polishing liquid may contain a pH adjusting agent in order to adjust the pH to the above range. The pH adjuster is not particularly limited, and examples thereof include acids such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and boric acid; bases such as sodium hydroxide, ammonia, potassium hydroxide and calcium hydroxide. Moreover, pH can also be adjusted using 3rd additives, such as an acetic acid mentioned above. From the viewpoint of improving productivity, a CMP polishing liquid may be prepared without using a pH adjuster, and such a CMP polishing liquid may be applied to CMP as it is.

<Preparation method and usage of polishing liquid for CMP>
The polishing liquid for CMP can be classified into (A) normal type, (B) concentrated type, and (C) two-liquid type, and the preparation method and usage differ depending on the type. (A) The normal type is a polishing liquid that can be used as it is without pretreatment such as dilution during polishing. (B) The concentrated type is a polishing liquid in which the contents are concentrated in comparison with the (A) normal type in consideration of convenience of storage or transportation. (C) The two-liquid type is divided into a liquid A containing a certain component and a liquid B containing other components at the time of storage or transportation, and the liquid A and the liquid B are mixed and used at the time of use. A polishing liquid.

  (A) The normal type can be obtained by dissolving or dispersing the abrasive grains, the first additive, the second additive, and, if necessary, other components in water, which is the main dispersion medium. it can. For example, 100 parts by weight of polishing slurry for CMP having 0.5 parts by weight of abrasive grains, 0.1 parts by weight of first additive, and 0.001 parts by weight of second additive. To prepare 1000 g, the CMP polishing liquid 1000 g may be adjusted to contain 5 g of abrasive grains, 1 g of the first additive, and 0.01 g of the second additive.

  The CMP polishing liquid can be prepared using, for example, a stirrer, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like. In addition, you may perform the micronization process of an abrasive grain in the preparation process of polishing liquid for CMP so that the average particle diameter of an abrasive grain may become a desired range. The fine graining treatment of the abrasive grains can be carried out by a sedimentation classification method or a method using a high pressure homogenizer. The sedimentation classification method is a method having a step of forcibly sedimenting coarse particles of slurry containing abrasive grains with a centrifuge and a step of taking out only the supernatant. A method using a high-pressure homogenizer is a method in which abrasive grains in a dispersion medium collide with each other at a high pressure.

  (B) The concentrated type is diluted with water so that the content of the contained component becomes a desired content immediately before use. After dilution, (A) Liquid characteristics (pH, grain size of abrasive grains, etc.) and polishing characteristics (for example, polishing rate of silicon oxide, polishing selectivity ratio of silicon oxide to silicon nitride, etc.) comparable to normal type can be reproduced. Until then, stirring or abrasive dispersion may be performed for an arbitrary time. (B) In the concentration type, the volume is reduced according to the degree of concentration, so that the cost for storage and transportation can be reduced.

  The concentration factor is preferably 1.5 times or more, more preferably 2 times or more, still more preferably 3 times or more, and particularly preferably 5 times or more. When the concentration factor is 1.5 times or more, there is a tendency that merits relating to storage and transportation can be obtained as compared with the case of less than 1.5 times. The concentration factor is preferably 40 times or less, more preferably 20 times or less, and still more preferably 15 times or less. When the concentration factor is 40 times or less, there is a tendency that aggregation of abrasive grains is easily suppressed as compared with a case where the concentration rate exceeds 40 times.

  (B) The point to be noted when using the concentrated type is that the pH changes before and after dilution with water. (A) To prepare a polishing liquid having the same pH as that of the normal type from (B) the concentrated type, the pH of the concentrated type polishing liquid should be set low in advance, taking into account the increase in pH due to mixing with water. That's fine. For example, when water (pH: about 5.6) in which carbon dioxide is dissolved is used and (B) concentrated type polishing liquid having pH 4.0 is diluted 10 times, the pH of the diluted polishing liquid is 4. It rises to about 3.

  (B) The pH of the concentrated type is preferably 1.5 to 7.0 from the viewpoint of obtaining a polishing liquid having a suitable pH after dilution with water. The lower limit of pH is preferably 1.5 or more, and more preferably 2.0 or more. The upper limit of pH is preferably 7.0 or less, more preferably 6.0 or less, and even more preferably 5.0 or less, from the viewpoint of easily suppressing the aggregation of abrasive grains.

  (C) 2 liquid type has the advantage that it can avoid agglomeration etc. of an abrasive grain compared with (B) concentration type. The component which each of the liquid A and the liquid B contains is arbitrary. For example, a slurry containing abrasive grains and a surfactant blended as necessary is prepared as liquid A, and the first additive, the second additive, and other blended as necessary A solution containing these components can be prepared as liquid B. In this case, in order to improve the dispersibility of the abrasive grains in the liquid A, any acid or alkali may be added to the liquid A to adjust the pH.

  (C) The two-liquid type polishing liquid is useful when the polishing characteristics deteriorate in a relatively short time due to agglomeration of abrasive grains in the state where the respective components are mixed. In addition, from the viewpoint of cost reduction for storage and transportation, at least one of the liquid A and the liquid B may be a concentrated type. In this case, the liquid A, the liquid B, and water may be mixed when using the polishing liquid. The concentration ratio and pH of the liquid A or the liquid B are arbitrary, and the liquid characteristics and polishing characteristics of the final mixture may be the same as those of the (A) normal type polishing liquid.

<Polishing method>
The polishing method according to the present embodiment is a polishing method using the CMP polishing liquid according to the present embodiment. For example, a polishing liquid in which the content and pH of each component are adjusted is used, and an insulating material is provided on the surface. A substrate having (for example, an inorganic insulating material such as silicon oxide) is planarized by a CMP technique. The insulating material (such as silicon oxide) may be in the form of a film (such as a silicon oxide film). Specifically, the base includes a base having a concave portion and a convex on the surface, a stopper disposed on the convex of the base, and an insulating material covering the base and the stopper. It is. Specifically, the polishing method according to this embodiment includes a first polishing step for polishing the insulating material in the base, and a second polishing step for polishing the portion of the insulating material on the stopper to expose the stopper. And a polishing step. In the first polishing step, the insulating material is polished without exposing the stopper. Further, in the polishing method according to the present embodiment, in the first polishing step, the insulating material is supplied by the polishing pad while supplying the CMP polishing liquid according to the present embodiment between the insulating material and the polishing pad. Can be polished.

  The polishing method according to this embodiment is suitable for polishing a substrate having an insulating material (for example, an inorganic insulating material such as silicon oxide) on the surface in the following device manufacturing process. Devices include, for example, individual semiconductors such as diodes, transistors, compound semiconductors, thermistors, varistors, thyristors; DRAM (dynamic random access memory), SRAM (static random access memory), EPROM (erasable programmable)・ Storage elements such as read only memory (ROM), mask ROM (mask read only memory), EEPROM (electrically erasable programmable read only memory), flash memory; microprocessor, DSP, ASIC, etc. Theoretical circuit element; integrated circuit element such as compound semiconductor represented by MMIC (monolithic microwave integrated circuit); hybrid integrated circuit (hybrid IC), light emitting diode Such as a photoelectric conversion element such as a charge coupled device and the like.

  The polishing liquid for CMP according to the present embodiment has an effect of eliminating the dependency on density while achieving high step removal performance. Such a polishing method using a polishing liquid can also be applied to a substrate for which it has been difficult to achieve high step-removability and the effect of eliminating the dependency on density by a conventional method using a polishing liquid for CMP. .

  The polishing method according to this embodiment is particularly suitable for flattening a surface to be polished having a step (unevenness) on the surface. Examples of the substrate having such a surface to be polished include a semiconductor device for logic. In addition, this polishing method is suitable for polishing a substrate having a surface including a portion where concave portions or convex portions are provided in a T shape or a lattice shape when viewed from above. For example, an insulating material (eg, an inorganic insulating material such as silicon oxide) provided on the surface of a semiconductor device (eg, DRAM or flash memory) including a semiconductor substrate having memory cells can be polished at a high speed. In addition, an insulating material (for example, an inorganic insulating material such as silicon oxide) provided on the surface of the 3D-NAND flash memory, which tends to show the dependency on density, can be polished with high speed and flatness. These are difficult to achieve a high step-removability and the effect of eliminating the dependency on the density by the conventional method using the CMP polishing liquid, and the CMP polishing liquid according to the present embodiment is high. It shows that it has the effect of eliminating the dependence on density while achieving step removal.

  The substrate to which the polishing method can be applied is not limited to a substrate in which the entire substrate surface is formed of a silicon oxide film, but a silicon nitride film, a polycrystalline silicon film, or the like is further formed on the substrate surface in addition to the silicon oxide film. It may be. In addition, the polishing method includes an inorganic insulating film such as a silicon oxide film, a glass film, and a silicon nitride film, a polysilicon film, Al, Cu, Ti, TiN, W, Ta, and TaN on a wiring board having a predetermined wiring. The present invention can also be applied to a substrate on which a film mainly containing etc. is formed.

Examples of the method for forming a silicon oxide film on the substrate surface include a low pressure CVD method and a plasma CVD method. In the formation of the silicon oxide film by the low pressure CVD method, monosilane (SiH ₄ ) can be used as the Si source, and oxygen (O ₂ ) can be used as the oxygen source. A silicon oxide film is formed by performing this SiH ₄ —O ₂ -based oxidation reaction at a low temperature of 400 ° C. or lower. In some cases, heat treatment is performed at a temperature of 1000 ° C. or lower after CVD.

The plasma CVD method has an advantage that a chemical reaction requiring a high temperature can be performed at a low temperature under normal thermal equilibrium. There are two plasma generation methods, a capacitive coupling type and an inductive coupling type. As the reaction gas, for _{example, SiH 4, SiH 4 -N 2} O -containing gas using _{N 2} O as oxygen source, and, _{TEOS-O 2} system using tetraethoxysilane (TEOS) as an Si source as Si source Gas (TEOS-plasma CVD method) can be used. The substrate temperature is preferably in the range of 250 to 400 ° C. The reaction pressure is preferably in the range of 67 to 400 Pa.

When doping silicon (P) with phosphorus (P) in order to achieve surface planarization by high-temperature reflow, it is preferable to use a SiH ₄ —O ₂ —PH ₃ -based reactive gas. Thus, the silicon oxide film to be polished may be doped with an element such as phosphorus or boron.

Similarly to the silicon oxide film, the silicon nitride film can be formed by a low pressure CVD method, a plasma CVD method, or the like. In the low pressure CVD method, for example, dichlorosilane (SiH ₂ Cl ₂ ) can be used as the Si source, and ammonia (NH ₃ ) can be used as the nitrogen source. A silicon nitride film is formed by performing this SiH ₂ Cl ₂ —NH ₃ oxidation reaction at a high temperature of 900 ° C. Examples of the reactive gas in the plasma CVD method include SiH ₄ —NH ₃ gas using SiH ₄ as a Si source and NH ₃ as a nitrogen source. In this case, the substrate temperature is preferably 300 to 400 ° C.

  With reference to FIG. 2, a process of forming an STI structure on a substrate (wafer) by CMP in the polishing method according to the present embodiment will be described. FIG. 2 is a schematic cross-sectional view showing a process in which a silicon oxide film is polished to form an STI structure. As shown in FIG. 2 (a), the substrate (base body) includes a silicon substrate (base material) 1 having concave and convex portions on the surface, and a silicon nitride film (stopper) disposed on the convex portions of the silicon substrate 1. ) 2 and a silicon oxide film (insulating material) 3 covering the silicon substrate 1 and the silicon nitride film 2. The polishing method according to this embodiment includes a first polishing step (roughing step) for polishing the silicon oxide film 3 with high step removal performance and a high polishing rate, and the remaining silicon oxide film so that the silicon nitride film 2 is exposed. And a second polishing step (finishing step) for polishing 3 at a high polishing rate.

  FIG. 2A is a cross-sectional view showing the substrate before polishing. FIG. 2B is a cross-sectional view showing the substrate after the first polishing step. FIG. 2C is a cross-sectional view showing the substrate after the second polishing step. As shown in these figures, in the process of forming the STI structure, in order to eliminate the step D of the silicon oxide film 3 formed on the silicon substrate 1, unnecessary protruding portions are preferentially processed by CMP. Remove. Note that a silicon nitride film (stopper film) 2 having a low polishing rate is formed in advance on the convex portion under the silicon oxide film 3 in order to stop polishing appropriately when the surface is flattened. By passing through the first polishing step and the second polishing step, the step (elevation difference in film thickness) D of the silicon oxide film 3 is eliminated, and the element isolation structure having the embedded portion 5 is formed.

  In order to polish the silicon oxide film 3, a substrate is disposed on the polishing pad so that the surface of the silicon oxide film 3 and the polishing pad are in contact with each other, and the surface of the silicon oxide film 3 is polished with the polishing pad. More specifically, the surface to be polished of the silicon oxide film 3 is pressed against the polishing pad of the polishing surface plate, and the CMP polishing liquid is supplied between the surface to be polished and the polishing pad. By moving, the silicon oxide film 3 is polished by the polishing pad.

  The CMP polishing liquid according to the present embodiment has a high level difference removing property and can be applied to both the first and second polishing steps. In addition, the CMP polishing liquid according to the present embodiment can be suitably used in the first polishing process, particularly in terms of having a high step removing property and an effect of eliminating the dependency on the density. The second polishing process Can also be suitably used. In the CMP polishing liquid according to this embodiment, the insulating material to be polished in the first polishing step preferably contains silicon oxide.

  As the polishing apparatus, for example, an apparatus provided with a holder for holding the substrate, a polishing surface plate on which the polishing pad is attached, and means for supplying a polishing liquid onto the polishing pad is suitable. Examples of the polishing apparatus include polishing apparatuses (model numbers: EPO-111, EPO-222, FREX200, FREX300) manufactured by Ebara Corporation, and polishing apparatuses manufactured by Applied Materials (AMAT) (trade name: Mirara 3400, Reflexion polishing machine). Can be mentioned. There is no restriction | limiting in particular as a polishing pad, For example, a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used. Further, the polishing pad is preferably subjected to groove processing so that the polishing liquid is accumulated.

The polishing conditions are not particularly limited, but from the viewpoint of preventing the substrate from popping out, the rotation speed of the polishing platen is preferably 200 min ⁻¹ or less, and the pressure (working load) applied to the substrate is set on the surface to be polished. From the viewpoint of suppressing scratches, 100 kPa or less is preferable. During polishing, it is preferable to continuously supply the polishing liquid to the polishing pad by a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with polishing liquid.

  After the polishing, it is preferable that the substrate is thoroughly washed in running water, and further, water droplets adhering to the substrate are removed by a spin dryer or the like and then dried.

  By polishing in this way, surface irregularities can be eliminated and a smooth surface can be obtained over the entire surface of the substrate. A substrate having a desired number of layers can be manufactured by repeating the formation of the material to be polished and the step of polishing the material a predetermined number of times.

  The substrate thus obtained can be used as various electronic parts and mechanical parts. Specific examples include: semiconductor elements; optical glasses such as photomasks, lenses, and prisms; inorganic conductive films such as ITO; optical integrated circuits / optical switching elements / optical waveguides composed of glass and crystalline materials; Examples include optical single crystals such as scintillators; solid laser single crystals; sapphire substrates for blue laser LEDs; semiconductor single crystals such as SiC, GaP and GaAs; glass substrates for magnetic disks; magnetic heads and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

(Production of abrasive grains)
40 kg of cerium carbonate hydrate was placed in an alumina container and calcined in air at 830 ° C. for 2 hours to obtain 20 kg of a yellowish white powder. This powder was subjected to phase identification by X-ray diffraction, and it was confirmed that the powder contained polycrystalline cerium oxide. When the particle diameter of the powder obtained by baking was observed with SEM, it was 20-100 micrometers. Next, 20 kg of cerium oxide powder was dry-ground using a jet mill. When the cerium oxide powder after pulverization was observed with an SEM, it was confirmed that polycrystalline cerium oxide particles having crystal grain boundaries were contained. The specific surface area of the cerium oxide powder was 9.4 m ² / g. The specific surface area was measured by the BET method.

(Preparation of polishing liquid for CMP)
15 kg of the cerium oxide powder obtained above and 84.7 kg of deionized water were placed in a container and mixed. Further, 0.3 kg of 1N aqueous acetic acid solution was added and stirred for 10 minutes to obtain a cerium oxide mixed solution. The obtained cerium oxide mixed solution was fed to another container over 30 minutes. In the meantime, ultrasonic irradiation was performed on the cerium oxide mixed solution at an ultrasonic frequency of 400 kHz in the pipe for feeding the liquid.

  500 g of cerium oxide mixed solution was sampled in each of four 500 mL beakers and centrifuged. Centrifugation was performed for 2 minutes under conditions such that the centrifugal force applied to the outer periphery was 500G. The cerium oxide that settled at the bottom of the beaker was recovered, and the supernatant (liquid phase) was collected. The abrasive content was adjusted to 0.5% by mass based on the total mass of the liquid phase. Then, as a result of measuring the average particle diameter of abrasive grains using a dynamic light scattering particle size distribution meter (trade name: LA-920, manufactured by Horiba, Ltd.), the average particle diameter was 150 nm.

  The abrasive grains obtained above, the first additive listed in Tables 1 and 2, the third additive, and deionized water are mixed to obtain abrasive grains (5% by mass), first And a slurry containing a third additive (0.9% by mass). Next, after diluting the slurry (abrasive grain content: 5 mass%) with deionized water, the second additives listed in Tables 1 and 2 were added and stirred for 5 minutes or more. This obtained the polishing liquid concerning each Example and a comparative example. Tables 1 and 2 show the components and contents of each polishing liquid (contents based on the total mass of the polishing liquid). Note that maltol is 3-hydroxy-2-methyl-4-pyrone, and kojic acid is 5-hydroxy-2- (hydroxymethyl) -4-pyrone.

  When the average particle diameter of the abrasive grains in the polishing liquid was measured using a dynamic light scattering particle size distribution analyzer (trade name: LA-920, manufactured by Horiba, Ltd.), the average particle diameter was 150 nm in all cases. .

The pH of the polishing liquid was measured under the following conditions.
Measurement temperature: 25 ° C
Measuring device: manufactured by Electrochemical Instrument Co., Ltd., model number PHL-40
Measurement method: Standard buffer (phthalate pH buffer, pH: 4.01 (25 ° C.); neutral phosphate pH buffer, pH: 6.86 (25 ° C.); borate pH buffer, After calibrating three points using pH: 9.18 (25 ° C.), the electrode was placed in the polishing liquid, and the pH after being stabilized for 3 minutes or more was measured with the measuring device.

(Polishing property evaluation)
[Wafer preparation]
Using each of the CMP polishing liquids prepared as described above, a blanket wafer having a silicon oxide film on the surface was polished to obtain a polishing rate (a blanket wafer polishing rate). A blanket wafer is a wafer having a silicon oxide film with a thickness of 1000 nm disposed on a silicon substrate having a diameter of 200 mm.

  Further, a patterned wafer having an uneven silicon oxide film as a film to be polished was prepared. In this pattern wafer, a silicon nitride film (thickness: 100 nm) is formed as a stopper film on a part of a silicon substrate having a diameter of 200 mm, and then a recess is formed by etching the silicon substrate without the silicon nitride film by 350 nm. Then, a 600 nm silicon oxide film was formed on the stopper film and in the recess by plasma CVD. The pattern wafer has a pattern of Line / Space = 50 μm / 50 μm.

[Wafer polishing]
The blanket wafer and the pattern wafer were polished using a polishing apparatus (product name: Mirra 3400, manufactured by Applied Materials). The wafer was set in a holder having a suction pad for attaching the wafer. Further, a polishing pad made of porous urethane resin (k-groove groove, manufactured by Rodel, model number: IC-1010) was attached to a polishing surface plate having a diameter of 500 mm.

  The holder was placed on the polishing pad with the silicon oxide film forming surface of the wafer facing down. The load (wafer pressing pressure) was set to 34 kPa (5 psi).

Then, while each of the CMP polishing liquids prepared as described above is dripped at a flow rate of 200 mL / min onto the polishing pad attached to the polishing surface plate, the polishing surface plate and the wafer are each rotated at a speed of 103 min ^−1. The silicon oxide film was polished by rotating at 97 min ⁻¹ . Thereafter, the polished wafer was thoroughly washed with pure water and then dried.

[Evaluation of step removal]
Using a light interference type film thickness measuring device (trade name: RE-3000, manufactured by Dainippon Screen Mfg. Co., Ltd.), the amount of change in film thickness of the silicon oxide film before and after polishing on the convex portion of the pattern wafer was measured. The amount of change in film thickness when polishing the initial 60 seconds of the pattern wafer is defined as the pattern wafer polishing rate (PTW), and the value obtained by dividing the pattern wafer polishing rate by the blanket wafer polishing rate (BKT) (PTW / BKT) is removed. Calculated as gender. In addition, it means that level | step difference removal property is so high that the said numerical value is high.

[Evaluation of density dependence]
The convex portions in the same pattern in the patterned wafer (die), the fastest and the film thickness of the silicon oxide film polishing proceeded portion (SiO ₂ film), slowest polishing proceeded portion of the silicon oxide film (SiO ₂ The difference from the film thickness was calculated. The point of time when the film thickness of the silicon oxide film where the polishing progressed most rapidly became 0 nm was defined as the polishing end point, and the minimum value (0 nm) of the remaining film. The film thickness of the silicon oxide film in the part where polishing progressed the latest was taken as the maximum value of the remaining film. The difference between the maximum value and the minimum value of the remaining film was calculated, and the relative values of Examples 1 to 6 and Comparative Examples 1 to 4 when the difference between the maximum value and the minimum value of the remaining film in Comparative Example 5 was 1.0. The density dependence was evaluated based on the relative value. Note that the smaller the relative value is, the less the density dependency is generated.

[Evaluation of load dependency]
Using the polishing slurry for CMP of Examples 1 to 3, 5 and Comparative Example 1, the polishing rate was calculated by polishing the blanket wafer under the same conditions as above except that the load was changed to each load shown in Table 3 below. The load dependency was evaluated. FIG. 3 is a graph in which the load is plotted on the horizontal axis and the polishing rate at the load is plotted on the vertical axis.

  From the results of Tables 1 and 2, a first additive containing a 4-pyrone compound and a second additive containing a cationic polymer having a structural unit derived from a quaternary ammonium salt-containing monomer were used. It was shown that the polishing liquid according to Examples 1 to 6 can eliminate the density dependency while achieving high level difference removability as compared with the polishing liquid according to Comparative Examples 1 to 5. In particular, in Examples 3 and 4 using a diallyldimethylammonium chloride homopolymer, it was shown that a particularly excellent effect was exhibited in eliminating the density dependency. Further, from the results of Table 3 and FIG. 3, it was shown that the polishing liquids according to Examples 1 to 3 and 5 have a specific load dependency as compared with the polishing liquid according to Comparative Example 1. Such a unique load dependency protects the concave portion of the pattern wafer, and can exhibit a phenomenon in which the convex portion is polished at a high polishing rate.

  The inventors have described the best mode for carrying out the invention in the specification. Preferred variations similar to these may become apparent when reading the above description by one of ordinary skill in the art. The inventors of the present invention are fully aware of the implementation of different forms of the present invention and the implementation of similar forms of application of the foundation of the present invention. Moreover, the present invention can use, as its principle, all the modifications described in the claims and any combination of the various elements. All possible combinations thereof are included in the invention unless otherwise specified herein or otherwise clearly denied by context.

  ADVANTAGE OF THE INVENTION According to this invention, when the insulating material (for example, inorganic insulating materials, such as silicon oxide) which has an unevenness | corrugation is grind | polished, the polishing liquid for CMP which can achieve high level | step difference removal property, and the grinding | polishing method using the same can do. In addition, according to the present invention, it is possible to eliminate the density dependency while achieving high level difference removability.

  DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... Stopper film | membrane (silicon nitride film) 3 ... Silicon oxide film, 5 ... Embedded part, A1 ... Area | region with a high level | step difference, A2 ... Area | region with a rough level | step difference, B ... Base material, C ... Insulating material , D: steps of the silicon oxide film.

Claims (22)

First polishing the insulating material in a base material having a base material having a concave portion and a convex portion on the surface, a stopper disposed on the convex portion of the base material, and an insulating material covering the base material and the stopper. Polishing process of
A second polishing step for polishing the portion of the insulating material on the stopper to expose the stopper, and a polishing liquid used in the first polishing step in a polishing method comprising:
Containing abrasive grains, a first additive, a second additive, and water,
The first additive includes a 4-pyrone compound represented by the following general formula (1):
A polishing slurry for CMP, wherein the second additive comprises a cationic polymer having a structural unit derived from a quaternary ammonium salt-containing monomer.

[In formula (1), X ¹¹ , X ¹² and X ¹³ are each independently a hydrogen atom or a monovalent substituent. ]   The first additive comprises 3-hydroxy-2-methyl-4-pyrone, 5-hydroxy-2- (hydroxymethyl) -4-pyrone, and 2-ethyl-3-hydroxy-4-pyrone. The polishing slurry for CMP according to claim 1, comprising at least one compound selected from the group.   The second additive is vinylpyrrolidone / dimethylaminoethyl methacrylate diethyl sulfate copolymer, diallyldimethylammonium chloride homopolymer, diallyldimethylammonium chloride / acrylamide copolymer, and diallylmethylethylammonium ethyl sulfate homopolymer The polishing slurry for CMP according to claim 1 or 2, comprising at least one compound selected from the group consisting of polymers.   The polishing slurry for CMP according to any one of claims 1 to 3, which does not contain a polymer compound having an aromatic ring and a polyoxyalkylene chain.   The polishing liquid for CMP as described in any one of Claims 1-4 whose pH is 8.0 or less.   The polishing liquid for CMP as described in any one of Claims 1-5 whose pH is 2.0-5.0.   The polishing liquid for CMP as described in any one of Claims 1-6 which further contains a pH adjuster.   The polishing liquid for CMP according to any one of claims 1 to 7, wherein the content of the first additive is 0.001 to 5 parts by mass with respect to 100 parts by mass of the polishing liquid.   The polishing liquid for CMP according to any one of claims 1 to 8, wherein the content of the second additive is 0.00001 to 5 parts by mass with respect to 100 parts by mass of the polishing liquid.   The polishing slurry for CMP according to any one of claims 1 to 9, wherein the content of the abrasive grains is 0.01 to 10 parts by mass with respect to 100 parts by mass of the polishing solution.   The polishing liquid for CMP as described in any one of Claims 1-10 whose average particle diameter of the said abrasive grain is 50-500 nm.   The polishing liquid for CMP as described in any one of Claims 1-11 in which the said abrasive grain contains a cerium type compound.   The polishing slurry for CMP according to claim 12, wherein the cerium-based compound is cerium oxide.   The polishing slurry for CMP as described in any one of Claims 1-13 in which the said abrasive grain contains the polycrystalline cerium oxide which has a crystal grain boundary.   The polishing liquid for CMP as described in any one of Claims 1-14 which further contains a nonionic surfactant.   The polishing slurry for CMP according to any one of claims 1 to 15, further comprising a saturated monocarboxylic acid.   The polishing slurry for CMP according to claim 16, wherein the saturated monocarboxylic acid has 2 to 6 carbon atoms.   The saturated monocarboxylic acid is acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, hydroangelic acid, caproic acid, 2-methylpentanoic acid, 4-methylpentanoic acid, 2,3- The polishing slurry for CMP according to claim 16 or 17, which is at least one compound selected from the group consisting of dimethylbutanoic acid, 2-ethylbutanoic acid, 2,2-dimethylbutanoic acid and 3,3-dimethylbutanoic acid. .   The polishing liquid for CMP according to any one of claims 16 to 18, wherein the content of the saturated monocarboxylic acid is 0.01 to 10 parts by mass with respect to 100 parts by mass of the polishing liquid. First polishing the insulating material in a base material having a base material having a concave portion and a convex portion on the surface, a stopper disposed on the convex portion of the base material, and an insulating material covering the base material and the stopper. Polishing process of
A second polishing step of polishing a portion of the insulating material on the stopper to expose the stopper, and a polishing method comprising:
In the first polishing step, the insulating material is polished by the polishing pad while supplying the CMP polishing liquid according to any one of claims 1 to 19 between the insulating material and the polishing pad. , Polishing method.   The polishing method according to claim 20, wherein the base has a portion in which the concave portion or the convex portion is provided in a T shape or a lattice shape when viewed from above.   The polishing method according to claim 20 or 21, wherein the substrate is a semiconductor substrate having memory cells.

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