JP2016178099A - Polishing liquid for cmp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid for CMP, with which it is possible to suppress polishing scratches and dishing, and to achieve a higher polishing speed and cleaning performance.SOLUTION: A polishing liquid for CMP of the present invention is used for polishing a film to be polished by mixing, at the time of polishing, a polishing material slurry containing a polishing material, a dispersant and water, with an additive solution containing an additive that includes a carboxylic acid or a water-soluble organic polymer having a carboxylate group, an inorganic acid or an inorganic acid salt and water. Polishing material particles (10) used in the polishing material are particles having a core/shell structure, a core layer (2) containing an oxide of at least one element selected from among Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, W, Bi, Th and alkaline earth metals, and a shell layer (4) containing a cerium oxide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polishing liquid for CMP. More specifically, the present invention relates to a polishing slurry for CMP that can suppress polishing scratches and dishing and obtain a higher polishing rate and cleaning performance.

  As the degree of integration of semiconductor devices has increased and the number of layers has increased, the storage capacity of memory devices has increased dramatically. This is supported by the progress of miniaturization of processing technology, but despite the multilayer wiring, etc., the chip size becomes larger, the process increases with the miniaturization, and the cost of the chip is increased. .

  Under such circumstances, processing technology for high density and miniaturization has been researched and developed, and as one of them, CMP (Chemical Mechanical Polishing) technology has been introduced and widely adopted. By applying this CMP technique, for example, many miniaturization techniques such as planarization of interlayer insulating films and BPSG films (silicon dioxide films doped with boron, phosphorus, etc.) are realized in the manufacturing process of semiconductor elements. It was.

As such a miniaturization technique, for example, a so-called STI technique, known as miniaturization element isolation (Shallow Trench Isolation), is known. In the STI technique, CMP is used to remove an excess silicon oxide insulating film formed on a wafer substrate.
In this STI technique, in order to stop polishing, a stopper film such as silicon nitride having a low polishing rate is formed under the silicon oxide film. Therefore, it is desirable that the polishing liquid for CMP has a large polishing rate ratio between the silicon oxide film and the stopper film. In addition, various polishing materials have been studied so far in order to obtain flatness of the surface to be polished. .

  Conventionally, silica particles were generally used as abrasive particles used in CMP polishing liquids, but in the STI process, the selectivity between the polishing rate of the silicon oxide film and the polishing rate of the silicon nitride film is small. Further, cerium oxide particles having excellent polishing selectivity have been used.

For example, in Patent Documents 1 and 2, in an STI CMP process, an aqueous dispersion using cerium oxide as abrasive particles is used to obtain a surface to be polished having a high polishing rate and relatively few polishing flaws. Disclosed technology.
However, in this technique, for example, when excessive polishing is performed to remove the polishing residue other than the trench groove, the silicon oxide film embedded in the trench groove is polished, and a structural defect such as a depression is generated. A phenomenon called dishing occurs, and planarization may be insufficient or electrical performance may deteriorate. The degree of dishing depends on the width of the trench groove, and the dishing tends to increase particularly in a wide trench groove.

Further, since contaminants on the substrate after polishing caused by impurities and abrasive particles in the polishing liquid used in the CMP process must be removed by the cleaning process before moving to the subsequent process, a cleaning method after CMP Many proposals have been made.
However, these conventional cleaning methods are effective when the abrasive particles in the polishing liquid are silica particles, but when the abrasive particles are cerium oxide particles, the cerium oxide particles are chemically compared to the silica particles. Since it is active and has an extremely high adhesion to the surface of the semiconductor substrate, there has been a serious problem that a sufficient cleaning effect cannot be expected.

Japanese Patent No. 3335667 JP-A-9-270402

  The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is to provide a polishing slurry for CMP that can suppress polishing scratches and dishing and obtain a higher polishing rate and cleaning performance. It is.

  In order to solve the above problems, the present inventor, in the process of examining the cause of the above problems, the abrasive particles used for the abrasive are particles having a core-shell structure, and the core layer has a specific element. And the shell layer contains cerium oxide, so that polishing scratches and dishing can be suppressed, and a higher polishing rate and cleaning performance can be obtained. The headline, the present invention has been reached.

  That is, the said subject which concerns on this invention is solved by the following means.

1. An abrasive slurry containing an abrasive, a dispersant and water, and an additive containing a carboxylic acid or a water-soluble organic polymer having a carboxylate group, an inorganic acid or an inorganic acid salt and water are mixed during polishing. A CMP polishing liquid used for polishing a film to be polished,
The abrasive particles used for the abrasive are particles having a core / shell structure,
The core layer includes aluminum (Al), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), Copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), indium (In), tin (Sn), yttrium (Y), gatrinium (Gd), terbium (Tb), From dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), tungsten (W), bismuth (Bi), thorium (Th) and alkaline earth metals Contains an oxide of at least one element selected, and
A polishing slurry for CMP, wherein the shell layer contains cerium oxide.

  2. The CMP polishing liquid has a pH of 3 to 6 at 25 ° C., and the total concentration of the water-soluble organic polymer having a carboxylic acid group or a carboxylic acid group is 0.01 to 0 based on the total mass of the polishing liquid. The polishing liquid for CMP according to item 1, wherein the polishing liquid is within a range of 0.5 mass%.

3. Further comprising an intermediate layer between the core layer and the shell layer; and
The intermediate layer includes aluminum (Al), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), and nickel (Ni). , Copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), indium (In), tin (Sn), yttrium (Y), gatrinium (Gd), terbium (Tb) , Dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), tungsten (W), bismuth (Bi), thorium (Th) and alkaline earth metals Item 1 or Item 2 containing an oxide of at least one element selected from cerium oxide CMP polishing slurry according.

  By the above means of the present invention, it is possible to provide a polishing slurry for CMP that can suppress polishing scratches and dishing, and can obtain a higher polishing rate and cleaning performance.

  The expression mechanism / action mechanism of the effect of the present invention is not clear, but is presumed as follows.

  Cerium oxide particles have a chemically active property known as a strong oxidant, and have the advantage that a higher polishing rate can be obtained compared to silica particles or alumina particles that perform only physical polishing. is there. However, when polishing scratches that can be visually observed enter, or when applied to polishing of an inorganic insulating film, it tends to chemically adhere to the surface of the insulating film, so that the cleaning property is remarkably deteriorated.

  In the present invention, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy are used for the core layer and the intermediate layer. , Ho, Er, Tm, Yb, Lu, W, Bi, Th, or a salt of at least one element selected from alkaline earth metals, for example, yttrium oxide, to prevent stress applied during polishing Thus, the particles are less likely to break than cerium oxide particles, and the particles remaining on the surface of the object to be polished can be significantly reduced. Furthermore, by containing an additive that adsorbs to the surface of the abrasive and prevents direct contact with the object to be polished, the additive adsorbed on the surface is peeled off only at the part where high pressure is applied, and only that part is removed. Polishing occurs due to chemical bonding and mechanical action. Thus, it is possible to further reduce residual particles by preventing excessive chemical bonding.

Schematic diagram showing a two-layer structure of abrasive particles according to the present invention Schematic diagram showing a three-layer structure of abrasive particles according to the present invention The graph which shows typically the composition of the 3 layer structure of the abrasive particle which concerns on this invention The graph which shows typically the composition of the 3 layer structure of the abrasive particle which concerns on this invention The graph which shows typically the composition of the 2 layer structure of the abrasive particle which concerns on this invention The graph which shows typically the composition of the 2 layer structure of the abrasive particle which concerns on this invention

  The polishing slurry for CMP of the present invention comprises an abrasive slurry containing an abrasive, a dispersing agent and water, an additive containing a water-soluble organic polymer having a carboxylic acid or a carboxylate group, an inorganic acid or an inorganic acid salt, and water. A polishing slurry for CMP that is used for polishing a film to be polished by mixing an additive liquid that is contained during polishing, and the abrasive particles used for the abrasive are particles having a core-shell structure. Aluminum (Al), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), Zinc (Zn), Gallium (Ga), Germanium (Ge), Zirconium (Zr), Indium (In), Tin (Sn), Yttrium (Y), Gatrinium (Gd), Terbium (Tb), Dis From rosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), tungsten (W), bismuth (Bi), thorium (Th) and alkaline earth metals An oxide of at least one element selected is contained, and the shell layer contains cerium oxide. This feature is a technical feature common to the inventions according to claims 1 to 3.

  As an embodiment of the present invention, the pH at 25 ° C. of the polishing liquid for CMP is in the range of 3 to 6 from the viewpoint of improving dispersion stability and suppressing polishing scratches by suppressing particle aggregation. And it is preferable that the sum total density | concentration of the water-soluble organic polymer which has a carboxylic acid group or a carboxylate group exists in the range of 0.01-0.5 mass% of polishing liquid total mass. In this embodiment, since the positive potential of the particle surface is increased, the additive is easily adsorbed on the particle surface, and the characteristics of the abrasive particles in the present invention can be further improved.

  Further, in the present invention, an intermediate layer is further provided between the core layer and the shell layer, and the intermediate layer includes aluminum (Al), scandium (Sc), titanium (Ti), vanadium (V), chromium. (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), indium (In), tin (Sn), yttrium (Y), gatrinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), tungsten (W), bismuth (Bi), thorium (Th) and an acid of at least one element selected from alkaline earth metals It is preferable from the viewpoint of improving the polishing rate and objects, and a cerium oxide are contained.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" showing a numerical range is used by the meaning containing the numerical value described before and behind that as a lower limit and an upper limit.

≪Abrasive material≫
<Layer configuration of abrasive particles>
As the abrasive according to the present invention, as shown in FIG. 1, an abrasive particle 10 having a two-layer core / shell structure having a core layer 2 and a shell layer 4 covering the core layer 2 is used.
The core layer 2 includes Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy, Ho, Er, Contains oxides of at least one element selected from Tm, Yb, Lu, W, Bi, Th or alkaline earth metals (calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra)) Has been.
The shell layer 4 contains cerium oxide.

As shown in FIG. 2, the layer structure of the abrasive particles includes a core layer 2, an intermediate layer 6 that covers the core layer 2, and a shell layer 4 that covers the intermediate layer 6 on the outer side. A three-layer structure is more preferable.
The intermediate layer 6 includes Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy, Ho, Er, An oxide of at least one element selected from Tm, Yb, Lu, W, Bi, Th, and an alkaline earth metal, and cerium oxide are contained.

More specifically, the abrasive particle 20 having a three-layer structure includes a core layer 2 containing an oxide such as yttrium oxide, and is formed outside the core layer 2 and contains an oxide such as yttrium oxide and cerium oxide. The intermediate layer 6 and the shell layer 4 formed on the outer side of the intermediate layer 6 and containing cerium oxide are included.
For example, as shown in FIG. 3, the core layer 2 contains almost no cerium oxide, and the oxide such as yttrium oxide is almost 100 mol%. The content of cerium oxide in the intermediate layer 6 changes in composition with a constant concentration gradient from the inner side of the intermediate layer 6 (core layer 2 side) to the outer side of the intermediate layer 6 (shell layer 4 side). (It has increased. The ratio of cerium oxide included in the intermediate layer 6 may be equal to or higher than the ratio of cerium oxide included in the core layer 2 and not higher than the ratio of cerium oxide included in the shell layer 4. The shell layer 4 formed outside the intermediate layer 6 contains cerium oxide at a ratio of approximately 100 mol%.
The ratio of cerium oxide contained in the shell layer 4 is preferably in the range of 50 to 100 mol%, and more preferably 75 mol% or more. By making the ratio of cerium oxide contained in the shell layer 4 serving as the surface of the abrasive particles close to 100 mol%, an excellent polishing rate of cerium oxide can be exhibited.

As another aspect, a three-layer structure as shown in FIG. 4 may be used.
That is, the ratio of the oxide such as yttrium oxide and cerium oxide contained in the intermediate layer 6 may be constant regardless of the distance from the center of the abrasive particles, and may be configured to be approximately half each. .

  The core layer 2 and the intermediate layer 6 form substantially one layer (hereinafter referred to as a composite layer 8), and the composite layer 8 contains cerium oxide with a predetermined concentration gradient. Abrasive particles having a two-layer structure of 8 and shell layer 4 may be used. Specifically, as shown in FIG. 5, the composition changes with a constant concentration gradient of cerium oxide content from the center of the abrasive particle 20 (center of the composite layer 8) toward the shell layer 4 side ( Increase).

  Further, as shown in FIG. 6, the ratio of the oxide such as yttrium oxide and cerium oxide contained in the composite layer 8 is constant regardless of the distance from the center of the abrasive particles 20, and is approximately half each. It may be configured as follows.

The oxide contained in the abrasive particles is not particularly limited as long as it is not easily broken by stress applied when used.
In addition, the oxide contained in the core layer 2 and the oxide contained in the intermediate layer 6 are preferably the same in order to maintain the bonding strength between the layers, but the present invention is not limited to this. The intermediate layer 6 may contain oxides of different elements.

<Characteristics of abrasive particles>
Abrasive particles have different required levels for the particle size depending on their use, but as the finished surface accuracy after polishing becomes higher, it is necessary to make the abrasive particles finer contained in the abrasive used. When used in the manufacturing process of a semiconductor device, the average particle size needs to be 2.0 μm or less. However, the smaller the particle size of the abrasive particles, the higher the finished surface accuracy after polishing, whereas the polishing rate tends to be slow. For example, with a particle size of less than 0.02 μm, a cerium-based abrasive The advantage that the polishing rate is higher than that of colloidal silica and other abrasives is lost. Therefore, the average particle diameter of the abrasive particles is preferably in the range of 0.02 to 2.0 μm, and more preferably in the range of 0.05 to 1.5 μm.
Further, in order to increase the planar accuracy after the polishing process, it is desirable to use an abrasive having a uniform particle size as much as possible and a small particle size distribution variation coefficient.

≪Method for producing abrasive particles≫
Although the manufacturing method of the abrasive particle 20 which has a 3 layer structure is shown as a manufacturing method of an abrasive particle below, it is an example and is not limited to this. Further, the present invention can be appropriately applied to a core / shell two-layer structure without the intermediate layer 6 and a two-layer structure in which the core layer 2 and the intermediate layer 6 are not distinguished.

The method for producing abrasive particles according to the present invention mainly comprises the following five steps.
(I) Core layer forming step (ii) Intermediate layer forming step (iii) Shell layer forming step (iv) Solid-liquid separation step (v) Firing step Hereinafter, each step will be described in order.
In the following, for the sake of convenience, each layer constituting the abrasive particle 20 is not composed of an oxide of a specific element but is composed of a salt such as carbonate, for the sake of convenience, the core layer 2, the intermediate layer 6, and the shell. This is referred to as layer 4.

(I) Core layer forming step In the core layer forming step, first, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd A urea compound is added to an aqueous solution containing a salt of at least one element selected from Tb, Dy, Ho, Er, Tm, Yb, Lu, W, Bi, Th and an alkaline earth metal, and Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, W, A first dispersion solution in which a basic carbonate of at least one element selected from Bi, Th, and an alkaline earth metal is dispersed is prepared.

Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, As the salt of at least one element selected from W, Bi, Th and alkaline earth metals, nitrates, hydrochlorides, sulfates and the like can be used, but it is preferable to use nitrates.
Examples of urea compounds include urea, urea salts (eg, nitrates, hydrochlorides, etc.), N, N′-dimethylacetylurea, N, N′-dibenzoylurea, benzenesulfonylurea, p-toluenesulfonylurea, Trimethylurea, tetraethylurea, tetramethylurea, triphenylurea, tetraphenylurea, N-benzoylurea, methylisourea, ethylisourea and the like can be mentioned, and urea is preferred.
In the following, a case where a basic carbonate is formed using urea will be described, but this is an example and the present invention is not limited to this.

Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, The ion concentration in the aqueous solution of at least one element selected from W, Bi, Th, and alkaline earth metal is in the range of 0.001 to 0.1 mol / L, and the urea concentration is 5 to 5 of the above-mentioned ion concentration. It is preferably 50 times. This is Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb. As long as the ion concentration and urea concentration in the aqueous solution of at least one element selected from Al, Lu, W, Bi, Th, and alkaline earth metal are within the above ranges, the resulting spherical shape exhibits monodispersity. This is because the abrasive particles can be synthesized.
The mixed aqueous solution is heated and stirred at 80 ° C. or higher to grow a basic carbonate dispersed in the aqueous solution (hereinafter referred to as a first dispersion solution) to be the core layer 2.
In the case of heating and stirring, the stirrer is not particularly limited as long as sufficient stirring efficiency can be obtained. However, in order to obtain higher stirring efficiency, it is preferable to use a rotor / stator type stirrer.

(Ii) Intermediate layer forming step In the intermediate layer forming step, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni are added to the first dispersion solution containing the basic carbonate formed in the core layer forming step. , Cu, Zn, Ga, Ge, Zr, In, Sn, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, W, Bi, Th, and alkaline earth metal formation A salt of an element used in the process, for example, an aqueous solution containing yttrium nitrate and an aqueous solution containing a cerium salt are added. By forming an intermediate layer 6 in which yttrium and cerium are mixed outside the basic carbonate of yttrium to be the core layer 2, the core layer 2 is further grown to form a basic carbonate having a larger particle diameter. Can be obtained.
The addition rate of each aqueous solution to be added to the first dispersion solution is preferably within a range of 0.003 to 3.0 mmol / min per liter of the first dispersion solution. In particular, the ratio of cerium in the total addition amount is less than 90 mol%. Preferably there is. This is because if the ratio of cerium in the addition rate and the addition amount is out of the range, it becomes difficult for the abrasive particles to be formed into spherical particles exhibiting monodispersity.
Moreover, it is preferable that a 1st dispersion solution is heated and stirred at 80 degreeC or more, adding each aqueous solution at the said speed | rate. This is because when heated and stirred at 80 ° C. or lower, decomposition of urea added in the core layer forming step does not proceed and particle formation is inhibited.
A dispersion solution in which particles having the intermediate layer 6 formed on the outside of the core layer 2 are dispersed is referred to as a second dispersion solution.

(Iii) Shell layer forming step In the shell layer forming step, an aqueous solution containing a cerium salt is added to the second dispersion solution in which the particles in which the intermediate layer 6 is formed outside the core layer 2 in the intermediate layer forming step are dispersed. The shell layer 4 containing a basic carbonate of cerium is formed outside the intermediate layer 6 to further grow the particles.
The aqueous solution containing a cerium salt is preferably added with heating and stirring at 80 ° C. or higher at an addition rate in the range of 0.003 to 3.0 mmol / min per liter of the second dispersion solution. This is because if the addition rate is out of the range, it becomes difficult for the formed abrasive particles to form spherical particles exhibiting monodispersity. As for the heating temperature, as in the case of the intermediate layer forming step, when heated and stirred at 80 ° C. or lower, the decomposition of urea added in the core layer forming step does not proceed and particle formation is inhibited.
A dispersion solution in which particles having the shell layer 4 formed outside the intermediate layer 6 are dispersed is referred to as a third dispersion solution.

(Iv) Solid-liquid separation step In the solid-liquid separation step, the particles formed up to the shell layer 4 are recovered by solid-liquid separation operation from the third dispersion obtained in the shell layer forming step, and an abrasive precursor is obtained. obtain.
In addition, after the solid-liquid separation process, the obtained abrasive precursor may be dried and transferred to a firing process described later, if necessary.

(V) Firing Step In the firing step, the basic carbonate abrasive precursor obtained by the solid-liquid separation step is fired at 400 ° C. or higher in air or in an oxidizing atmosphere. The baked abrasive precursor becomes an oxide, and becomes an abrasive particle whose outer side is covered with cerium oxide.

<< Abrasive slurry >>
The abrasive slurry according to the present invention can be obtained, for example, by dispersing a composition comprising abrasive particles having the above characteristics, a dispersant for the abrasive particles in water, and water.
Although there is no restriction | limiting in content of an abrasive particle, The inside of the range of 0.1-40 mass% is preferable with respect to 100 mass% of abrasive slurry from the ease of handling of an abrasive slurry, 0.5-20 mass % Is more preferable. If the content is 0.1% by mass or more, the polishing rate does not decrease, and if it is 40% by mass or less, aggregation of abrasive particles can be suppressed.
The content of the abrasive particles in the CMP polishing liquid when the abrasive slurry and the additive liquid described later are mixed is preferably in the range of 0.01 to 10% by mass, and 0.1 to 5% by mass. The range of is more preferable.

<Dispersant>
As the dispersant, one or two selected from a polymer dispersant, a water-soluble anionic surfactant, a water-soluble nonionic surfactant, a water-soluble cationic surfactant and a water-soluble amphoteric surfactant. More than one compound is used. Since it is used for semiconductor chip polishing, the content of impurities such as alkali metal ions such as sodium ions and potassium ions, halogen atoms and sulfur atoms in the dispersant is preferably suppressed to 10 ppm or less.

(Polymer dispersant)
Polymer dispersing agents include polymers of unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and itaconic acid, and ammonium salts or amine salts thereof, and unsaturated such as acrylic acid, methacrylic acid and maleic acid. Carboxylic acid, alkyl acrylates such as methyl acrylate and ethyl acrylate, hydroxyalkyl acrylates such as hydroxyethyl acrylate, alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, hydroxy methacrylates such as hydroxyethyl methacrylate Examples include copolymers with copolymer monomers such as alkyl, vinyl acetate, and vinyl alcohol, and ammonium salts or amine salts thereof.
The unsaturated carboxylic acid in these polymers or copolymers may be converted to an ammonium salt before polymerization. Moreover, it is preferable that the ratio of the unsaturated carboxylic acid in these polymers or copolymers exists in the range of 1-100 mol%, and it is more preferable that it exists in the range of 10-100 mol%.
The molecular weight of the polymer dispersant is a weight average molecular weight measured by gel permeation chromatography using a standard polystyrene calibration curve, preferably in the range of 100 to 100,000, more preferably in the range of 100 to 50,000, 1000 to More preferably within the range of 10,000. When the molecular weight of the dispersant is 100 or more, a sufficient polishing rate can be obtained when polishing the silicon oxide film or the silicon nitride film. When the molecular weight of the dispersant is 100,000 or less, the viscosity is low and the abrasive The storage stability of the slurry is improved.

Among the above dispersants, a polymer having an acrylic acid ammonium salt as a copolymerization component, a polyacrylic acid ammonium salt, or a polyacrylic acid amine salt is particularly preferable. The weight average molecular weight of the polyacrylic acid ammonium salt or the polyacrylic acid amine salt is preferably in the range of 1000 to 100,000, more preferably in the range of 3000 to 60000, and still more preferably in the range of 10,000 to 40000. The molecular weight distribution (weight average molecular weight / number average molecular weight) of the polyacrylic acid ammonium salt or polyacrylic acid amine salt is preferably in the range of 1.005 to 1.300, more preferably 1.100 to 1.250. And more preferably within the range of 1.150 to 1.200. If the weight average molecular weight is 1000 or more and the molecular weight distribution is 1.005 or more, the abrasive particles will not aggregate, and if the weight average molecular weight is 100,000 or less and the molecular weight distribution is 1.300 or less, the polishing rate ratio is There is no decline.
For the weight average molecular weight and number average molecular weight, those measured by gel permeation chromatography using a standard polystyrene calibration curve are used.

  Polyacrylic acid ammonium salt or polyacrylic acid amine salt is obtained by mixing polyacrylic acid with its carboxy group and equimolar amount of ammonia or amine and neutralizing it. An ammonia or amine ratio of 10 mol% or less is particularly preferable because high flatness can be obtained. The amount of free ammonia or amine that does not form a salt can be confirmed by quantifying ammonia or amine in the liquid in which an organic solvent is added and the polymer is precipitated and filtered.

(Water-soluble anionic surfactant)
Examples of the water-soluble anionic surfactant include lauryl sulfate triethanolamine, lauryl ammonium sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and the like.

(Water-soluble nonionic surfactant)
Examples of the water-soluble nonionic surfactant include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether. , Polyoxyethylene nonylphenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivatives, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate , Polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, tetraoleic acid Reoxyethylene sorbit, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2-hydroxyethyl methacrylate, alkyl alkanol Examples include amides.

(Water-soluble cationic surfactant)
Examples of the water-soluble cationic surfactant include polyvinyl pyrrolidone, coconut amine acetate, stearyl amine acetate and the like.

(Water-soluble amphoteric surfactant)
Examples of the water-soluble amphoteric surfactant include lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine and the like.

(Dispersant addition amount)
The said dispersing agent can be used individually or in combination of 2 or more types.
The amount of these dispersants added to the abrasive slurry is set to 0.000% by weight with respect to 100% by mass of the abrasive particles in view of the dispersibility of the particles in the slurry and prevention of settling, and the relationship between the polishing scratches and the amount of dispersant added. The range of 1 to 1.0% by mass is preferable, and the range of 0.3 to 0.7% by mass is more preferable. When the added amount of the dispersant is 0.1% by mass or more, since the dispersant concentration is sufficient, the particles do not cause aggregation between the particles without using the dispersant, and increase in polishing scratches accompanying the aggregation is suppressed. be able to. In addition, when the amount is 1.0% by mass or less, the dispersing agent molecules are not excessively caused to cause agglomeration between particles, which causes bridging, and this also suppresses an increase in polishing scratches. it can.

(Distributing means)
As a method of dispersing the abrasive particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill, or the like can be used in addition to the dispersion treatment with a normal stirrer.

≪Additive liquid≫
On the other hand, the additive liquid for the CMP polishing liquid contains an additive, an inorganic acid or an inorganic acid base, and water.

The additive is at least one selected from water-soluble organic polymers and anionic surfactants, and any of the above-described polymer dispersants and water-soluble anionic surfactants can be used.
In particular, the present invention is characterized in that the water-soluble organic polymer includes those having a carboxylic acid group or a carboxylic acid group. Specifically, a homopolymer of a monomer having a carboxylic acid group such as acrylic acid, methacrylic acid or maleic acid, or a homopolymer in which the carboxylic acid group portion of the polymer is a salt such as an ammonium salt Can be mentioned. A copolymer of a monomer having a carboxylic acid group and a monomer having a carboxylic acid group, or a monomer having a carboxylic acid group and a derivative such as an alkyl ester of carboxylic acid is also preferred. Furthermore, water-soluble organic polymers such as polyvinyl alcohol, and anionic surfactants such as ammonium oleate, ammonium lauryl sulfate, and triethanolamine lauryl sulfate can be preferably used.
In particular, a polymer having a carboxylic acid group or a salt thereof is preferable. Specific examples include polyacrylic acid or a polymer in which at least a part of the carboxylic acid group of polyacrylic acid is substituted with an ammonium carboxylate base (hereinafter referred to as ammonium polyacrylate).
In order to contain an inorganic acid or an inorganic acid salt, which will be described later, in the abrasive and adjust the pH (25 ° C.) of the CMP polishing liquid within the range of 3 to 6, ammonium polyacrylate is particularly preferable. When a water-soluble organic polymer such as ammonium polyacrylate is used as an additive, the molecular weight is preferably in the range of 1000 to 50000, and more preferably in the range of 2000 to 30000.

The additive may be the same as or different from the type of dispersant in the abrasive slurry.
Water-soluble organic polymer having carboxylic acid group or carboxylate group contained in CMP polishing liquid (dispersant contained in abrasive slurry contains water-soluble organic polymer having carboxylic acid group or carboxylate group) In this case, the concentration of the water-soluble organic polymer and the additive contained in the dispersant is preferably in the range of 0.01 to 0.5% by mass with respect to the total mass of the polishing liquid.

  Examples of the inorganic acid or inorganic acid salt include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, boric acid, carbonic acid, and ammonium salts or potassium salts thereof. The pH of the polishing liquid can be adjusted with an inorganic acid or an inorganic acid salt.

  The polishing slurry for CMP of the present invention is prepared by separately preparing an abrasive slurry and an additive solution and mixing them during polishing. The reason is that if the abrasive slurry and the additive liquid are stored in a mixed state, the abrasive particles aggregate to cause generation of polishing flaws and fluctuations in the polishing rate. For this reason, as a method of using the polishing slurry for CMP, the abrasive slurry and the additive solution are separately supplied onto the polishing platen and mixed on the polishing platen, or the abrasive slurry and the additive solution immediately before polishing. Are mixed and supplied onto a polishing surface plate. At this time, the mixing ratio of the abrasive slurry and the additive liquid is not particularly limited as long as it finally reaches a target concentration.

≪Polishing liquid pH≫
The pH (25 ° C.) of the CMP polishing liquid in the present invention is preferably in the range of 3-6. The pH is more preferably in the range of 3.5-6, and still more preferably in the range of 4-5. If the pH is 3 or more, it is not necessary to extremely reduce the amount of additive adsorbed on the surface of the silicon nitride film, which is necessary for the planarization characteristics, and the surface protection of the silicon nitride film is not insufficient. Further, the charge of the additive is not reduced, and the adsorbing power of the additive to the abrasive particles can be obtained. Furthermore, the charge of the additive adsorbed on the surface of the abrasive particles is not reduced, and the deterioration of the dispersion stability of the polishing liquid due to the reduction of electrical repulsion can be suppressed. Further, if the pH is 6 or less, the additive concentration can be reduced, so that dispersion stability of the abrasive particles can be obtained, and aggregation / sedimentation can be suppressed.

Adjustment of the pH of the polishing liquid for CMP may be performed by adding an acid or an alkali such as acetic acid or aqueous ammonia in addition to the inorganic acid or inorganic acid salt contained in the additive liquid.
Further, as a method of setting the pH of the polishing liquid to a predetermined value, a method of controlling the pH of the additive can also be employed. For example, when a copolymer composed of a carboxylic acid and a carboxylic acid salt is used as an additive, a method of adjusting the pH by controlling the polymerization ratio of the carboxylic acid and the carboxylic acid salt can also be employed.

  Although it does not specifically limit as a density | concentration adjustment method of an abrasive slurry and an addition liquid, For example, it is set as predetermined density | concentration by making both use density | concentration at the time of grinding | polishing twice and mixing both by mass ratio 1: 1. can do. For convenience of storage and transportation, for example, the concentration of both components is about 10 times the concentration of abrasive particles and additives, etc., and is diluted to twice the concentration during use. Alternatively, a predetermined concentration may be obtained by mixing at a mass ratio of 1: 1. Moreover, it can also be made to become a predetermined density | concentration by mixing a 10-times-concentration abrasive slurry, an additive liquid, and deionized water so that it may become 1: 1: 8 by mass ratio.

≪Other additives≫
The polishing slurry for CMP of the present invention may use the above abrasive slurry and additive solution as they are, but non-polymers such as N, N-diethylethanolamine, N, N-dimethylethanolamine, aminoethylethanolamine and the like. An additive may be added to the abrasive slurry or additive solution to provide a CMP polishing solution. These additives are preferably used so that the concentration in the final polishing liquid for CMP is 0.001 to 20% by mass, and is used to be 0.01 to 10% by mass. Is more preferable.

≪Method for manufacturing inorganic insulating film≫
Examples of a method for producing an inorganic insulating film in which the polishing slurry for CMP of the present invention is used include a low pressure CVD method and a plasma CVD method.
Silicon oxide film formation by the low pressure CVD method uses monosilane (SiH ₄ ) as the Si source and oxygen (O ₂ ) as the oxygen source. A silicon oxide film can be obtained 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. When doping phosphorus (P) in order to achieve surface flattening by high temperature reflow, it is preferable to use a SiH ₄ —O ₂ —PH ₃ -based reactive gas.
The plasma CVD method has an advantage that a chemical reaction requiring a high temperature can be performed at a low temperature under normal thermal equilibrium. There are two plasma generation methods, a capacitive coupling type and an inductive coupling type. As a reactive gas, SiH ₄ -N ₂ O-based gas using SiH ₄ as an Si source, N ₂ O as an oxygen source, and TEOS-O ₂ -based gas (TEOS) using tetraethoxysilane (TEOS) as an Si source. -Plasma CVD method). The substrate temperature is preferably in the range of 250 to 400 ° C., and the reaction pressure is preferably in the range of 67 to 400 Pa. The silicon oxide film may be doped with an element such as phosphorus or boron.

Similarly, the silicon nitride film formation by the low pressure CVD method uses dichlorosilane (SiH ₂ Cl ₂ ) as the Si source and ammonia (NH ₃ ) as the nitrogen source. A silicon nitride film is obtained by performing this SiH ₂ Cl ₂ —NH ₃ oxidation reaction at a high temperature of 900 ° C. In the plasma CVD method, examples of the reactive gas include SiH ₄ —NH ₃ -based gas using SiH ₄ as the Si source and NH ₃ as the nitrogen source. The substrate temperature is preferably in the range of 300 to 400 ° C.

As a substrate, a silicon oxide film or a silicon nitride film is formed on a semiconductor substrate such as a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed or a semiconductor substrate at a stage where only a circuit element is formed. Can be used. By polishing the silicon oxide film or silicon nitride film formed on the semiconductor substrate with the CMP polishing liquid, unevenness on the surface of the silicon oxide film or the like can be eliminated, and the entire surface of the semiconductor substrate can be made smooth.
It can also be used for shallow trench isolation. In order to use for shallow trench isolation, the ratio of the silicon oxide film polishing rate to the silicon nitride film polishing rate (silicon oxide film polishing rate / silicon nitride film polishing rate) needs to be 10 or more. If this ratio is too small, the difference between the silicon oxide film polishing rate and the silicon nitride film polishing rate becomes small, and it becomes impossible to stop polishing at a predetermined position when performing shallow trench isolation. In addition, when the polishing rate ratio is 50 or more, the polishing rate of the silicon nitride film is further reduced and polishing can be easily stopped, which is preferable for shallow trench isolation.

≪Polishing equipment≫
As a polishing apparatus, a general polishing apparatus having a surface plate to which a motor capable of changing the number of rotations and the like, to which a holder for holding a semiconductor substrate and a polishing cloth (pad) are attached, can be used. As the polishing cloth, a general nonwoven fabric, foamed polyurethane, porous fluororesin, or the like can be used, and is not particularly limited. Further, it is preferable that the polishing cloth is subjected to groove processing so as to hold the polishing liquid for CMP.
The polishing conditions are not limited, but the rotation speed of the surface plate is preferably low rotation of 200 rpm or less so that the semiconductor substrate does not jump out, and the pressure applied to the semiconductor substrate is 1 kg / cm ² or less so that no scratches are generated after polishing. Is preferred.
In order to be used for shallow trench isolation, it is necessary that scratches are less likely to occur during polishing. During polishing, slurry is continuously supplied to the polishing cloth with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of polishing cloth is always covered with the slurry.

≪Cleaning≫
The semiconductor substrate after completion of polishing is preferably washed in running water and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like.

  After forming the flattened shallow trench in this way, an aluminum wiring is formed on the silicon oxide insulating film, and the silicon oxide insulating film is formed again between the wirings and between the wirings by the above method. By polishing using a polishing liquid for CMP, irregularities on the surface of the insulating film are eliminated, and the entire surface of the semiconductor substrate is smoothed. By repeating this step a predetermined number of times, a semiconductor having a desired number of layers can be manufactured.

≪Others≫
The polishing slurry for CMP of the present invention includes not only a silicon oxide film formed on a semiconductor substrate but also an inorganic insulating film such as a silicon oxide film, glass, and silicon nitride film formed on a wiring board having a predetermined wiring, a photomask Optical glass such as lenses and prisms, inorganic conductive films such as ITO, optical integrated circuits composed of glass and crystalline materials, optical switching elements, optical waveguides, optical fiber end faces, scintillator optical single crystals, solid state lasers, etc. 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 can be polished.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in an Example, unless otherwise indicated, "mass%" is represented.

≪Preparation of abrasive particles≫
<Preparation of abrasive particles 1>
First, 10 L of a 0.01 mol / L yttrium nitric acid aqueous solution was prepared, urea was added to this aqueous solution so that the concentration of urea was 0.20 mol / L, and after sufficient stirring, the mixture was heated and stirred at 90 ° C. for 1 hour.
Subsequently, a mixed solution of 0.08 mol / L yttrium nitric acid aqueous solution 300 mL and 0.32 mol / L cerium nitric acid aqueous solution 300 mL, which had been mixed in advance, was added to the obtained dispersion solution at an addition rate of 10 mL / min. The mixture was added with stirring at 0 ° C.
Subsequently, 50 mL of 0.4 mol / L cerium nitric acid aqueous solution was added to the obtained dispersion solution at 90 ° C. with heating and stirring at an addition rate of 10 mL / min.
Finally, the abrasive precursor precipitated from the obtained dispersion solution was separated by a membrane filter and fired at 600 ° C. to produce abrasive particles 1.

The obtained abrasive particles 1 were confirmed to be monodisperse particles having an average particle diameter of 0.40 μm and a coefficient of variation of the particle diameter distribution of 11% from a scanning electron micrograph (SEM image) of 100 particles. . The particle size distribution variation coefficient was determined by the following formula.
Coefficient of variation (%) = (standard deviation of particle size distribution / average particle size) × 100

  Further, the abrasive particles 1 were subjected to cross-section processing with a focused ion beam (FB-2000A) manufactured by Hitachi High-Technologies, and a surface passing through the vicinity of the particle center was cut out. From the cut surface, elemental analysis was performed using STEM-EDX (HD-2000) manufactured by Hitachi High-Technologies, and the particle composition distribution was evaluated. As a result, the abrasive particle 1 has a three-layer structure. In the cross section, a core layer of yttrium oxide having a particle diameter of 0.3 μm, an intermediate layer having a layer thickness of 0.04 μm (yttrium oxide: cerium oxide = 1: 4), and a shell layer of cerium oxide having a layer thickness of 0.01 μm on the outermost surface. It was found that it was formed.

<Preparation of abrasive particles 2>
First, 10 L of a 0.05 mol / L yttrium nitric acid aqueous solution was prepared, and urea was added to this aqueous solution so as to have a concentration of 1.0 mol / L. After sufficiently stirring, the mixture was heated and stirred at 90 ° C. for 1 hour.
Subsequently, a mixed solution of 0.08 mol / L yttrium nitric acid aqueous solution 300 mL and 0.32 mol / L cerium nitric acid aqueous solution 300 mL, which had been mixed in advance, was added to the obtained dispersion solution at an addition rate of 10 mL / min. The mixture was added with stirring at 0 ° C.
Subsequently, 50 mL of 0.4 mol / L cerium nitric acid aqueous solution was added to the obtained dispersion solution at 90 ° C. with heating and stirring at an addition rate of 10 mL / min.
Finally, the abrasive precursor precipitated from the obtained dispersion solution was separated by a membrane filter and fired at 600 ° C. to produce abrasive particles 2.

  As in the case of the abrasive particle 1, as a result of evaluation of the particle size and elemental analysis of the abrasive particle 2, the abrasive particle 2 is a monodisperse particle having an average particle diameter of 0.62 μm and a coefficient of variation of 14%. It has a three-layer structure of a core layer (yttrium oxide) having a diameter of 0.57 μm, an intermediate layer (yttrium oxide: cerium oxide = 1: 4) having a layer thickness of 0.02 μm, and a shell layer (cerium oxide) having a layer thickness of 0.005 μm. It was.

<Preparation of abrasive particles 3>
First, 10 L of a 0.1 mol / L yttrium nitric acid aqueous solution was prepared, urea was added to this aqueous solution so as to be 2.0 mol / L, and after sufficient stirring, the mixture was heated and stirred at 90 ° C. for 1 hour.
Subsequently, a mixed solution of 0.08 mol / L yttrium nitric acid aqueous solution 300 mL and 0.32 mol / L cerium nitric acid aqueous solution 300 mL, which had been mixed in advance, was added to the obtained dispersion solution at an addition rate of 10 mL / min. The mixture was added with stirring at 0 ° C.
Subsequently, 50 mL of 0.4 mol / L cerium nitric acid aqueous solution was added to the obtained dispersion solution at 90 ° C. with heating and stirring at an addition rate of 10 mL / min.
Finally, the abrasive precursor precipitated from the obtained dispersion solution was separated by a membrane filter and fired at 600 ° C. to produce abrasive particles 3.

  As in the case of the abrasive particle 1, the particle size and elemental analysis of the abrasive particle 3 were evaluated. As a result, the abrasive particle 3 was a monodisperse particle having an average particle diameter of 0.75 μm and a coefficient of variation of 19% It has a three-layer structure of a core layer (yttrium oxide) having a diameter of 0.72 μm, an intermediate layer (yttrium oxide: cerium oxide = 1: 4) having a layer thickness of 0.01 μm, and a shell layer (cerium oxide) having a layer thickness of 0.005 μm. It was.

<Preparation of abrasive particles 4>
First, 10 L of a 0.01 mol / L yttrium nitric acid aqueous solution was prepared, urea was added to this aqueous solution so that the concentration of urea was 0.20 mol / L, and after sufficient stirring, the mixture was heated and stirred at 90 ° C. for 1 hour.
Subsequently, 300 mL of 0.4 mol / L cerium nitric acid aqueous solution (0.16 t) was added to the obtained dispersion solution at an addition rate of (10-0.16 t) mL / min. ) The mixture was added at 90 ° C. with heating and stirring at an addition rate of mL / min. However, t represents time (minutes).
Subsequently, 50 mL of 0.4 mol / L cerium nitric acid aqueous solution was added to the obtained dispersion solution at 90 ° C. with heating and stirring at an addition rate of 10 mL / min.
Finally, the abrasive precursor precipitated from the obtained dispersion solution was separated by a membrane filter and fired at 600 ° C. to produce abrasive particles 4.
In addition, the cerium oxide content in the intermediate layer of the abrasive particles 4 increased with a constant concentration gradient from the core layer side to the shell layer side.

  As in the case of the abrasive particle 1, the particle size and elemental analysis of the abrasive particle 4 were evaluated. As a result, the abrasive particle 4 was a monodisperse particle having an average particle size of 0.37 μm and a coefficient of variation of 15%. It has a three-layer structure of a core layer (yttrium oxide) having a diameter of 0.24 μm, an intermediate layer (yttrium oxide: cerium oxide = 1: 1) having a layer thickness of 0.06 μm, and a shell layer (cerium oxide) having a layer thickness of 0.005 μm. It was.

<Preparation of abrasive particles 5>
First, 10 L of an aqueous nitric acid solution containing 0.005 mol / L yttrium and 0.005 mol / L cerium was prepared and added so that urea was 0.20 mol / L. Stir for hours.
Next, a mixture of 600 mL of 0.08 mol / L yttrium nitric acid aqueous solution and 600 mL of 0.32 mol / L cerium nitric acid aqueous solution, which had been mixed in advance, was added to the obtained dispersion solution at an addition rate of 10 mL / min. The mixture was added with stirring at 0 ° C.
Subsequently, 50 mL of 0.4 mol / L cerium nitric acid aqueous solution was added to the obtained dispersion solution at 90 ° C. with heating and stirring at an addition rate of 10 mL / min.
Finally, the abrasive precursor precipitated from the obtained dispersion solution was separated by a membrane filter and fired at 600 ° C. to produce abrasive particles 5.

  As in the case of the abrasive particles 1, the particle size and elemental analysis of the abrasive particles 5 were evaluated. As a result, the abrasive particles 5 were monodisperse particles having an average particle diameter of 0.38 μm and a coefficient of variation of 19%, It was a two-layer structure consisting of a composite layer having a particle size of 0.31 μm and a shell layer (cerium oxide) having a layer thickness of 0.035 μm, in which yttrium oxide and cerium oxide were mixed. In the composite layer, the region having a diameter of 0.25 to 0.31 μm had a region with a higher cerium ratio than the center portion.

<Preparation of abrasive particles 6>
First, 10 L of a 0.01 mol / L yttrium nitric acid aqueous solution was prepared, urea was added to this aqueous solution so that the concentration of urea was 0.20 mol / L, and after sufficient stirring, the mixture was heated and stirred at 90 ° C. for 1 hour.
Next, 600 mL of a 0.40 mol / L yttrium nitric acid aqueous solution was added to the obtained dispersion solution at 90 ° C. with heating and stirring at an addition rate of 10 mL / min.
Subsequently, 50 mL of 0.4 mol / L cerium nitric acid aqueous solution was added to the obtained dispersion solution at 90 ° C. with heating and stirring at an addition rate of 10 mL / min.
Finally, the abrasive precursor precipitated from the obtained dispersion solution was separated by a membrane filter and fired at 600 ° C. to produce abrasive particles 6.

  As in the case of the abrasive particles 1, the particle size and elemental analysis of the abrasive particles 6 were evaluated. As a result, the abrasive particles 6 were monodisperse particles having an average particle size of 0.45 μm and a coefficient of variation of 15%. It had a two-layer structure of a core layer (yttrium oxide) having a diameter of 0.43 μm and a shell layer (cerium oxide) having a layer thickness of 0.01 μm.

<Preparation of abrasive particles 7>
First, 10 L of water was prepared, urea was added so as to have a concentration of 0.20 mol / L, and the mixture was sufficiently stirred and then heated and stirred until it reached 90 ° C.
Next, a mixture of 600 mL of 0.08 mol / L yttrium nitric acid aqueous solution and 600 mL of 0.32 mol / L cerium nitric acid aqueous solution, which had been mixed in advance, was added to the obtained dispersion solution at an addition rate of 10 mL / min. The mixture was added with stirring at 0 ° C.
Finally, the abrasive precursor precipitated from the obtained dispersion solution was separated by a membrane filter and fired at 600 ° C. to produce abrasive particles 7.

  As in the case of the abrasive particles 1, the particle size and elemental analysis of the abrasive particles 6 were evaluated. It was a one-layer structure of yttrium: cerium oxide = 1: 4.

<Preparation of abrasive particles 8>
By putting 2 kg of cerium carbonate hydrate in a platinum container and firing in air at 800 ° C. for 2 hours, about 1 kg of yellowish white powder was obtained. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. 1 kg of this cerium oxide powder was dry pulverized using a jet mill to produce abrasive particles 8.

  The abrasive particles 8 had a cerium oxide monolayer structure of polydispersed particles in which large polycrystalline particles having a particle size of 1 to 3 μm and polycrystalline particles having a particle size of 0.5 to 1 μm were mixed.

<Preparation of abrasive particles 9-11>
Abrasive particles 9 to 11 were produced in the same manner except that the yttrium nitric acid aqueous solution was changed to an aluminum nitric acid aqueous solution, a manganese nitric acid aqueous solution, and a tungsten nitric acid aqueous solution, respectively.

  Similarly to the abrasive particle 1, the particle diameter and elemental analysis of the abrasive particles 9 to 11 were evaluated.

  The abrasive particles 9 are monodisperse particles having an average particle size of 0.35 μm and a coefficient of variation of 15%, a core layer (aluminum oxide) having a particle size of 0.26 μm, and an intermediate layer (aluminum oxide: oxidized) having a layer thickness of 0.04 μm. Cerium = 1: 4) and a three-layer structure of a shell layer (cerium oxide) having a layer thickness of 0.005 μm.

  The abrasive particles 10 are monodisperse particles having an average particle size of 0.40 μm and a variation coefficient of 17%, a core layer (manganese oxide) having a particle size of 0.30 μm, and an intermediate layer (manganese oxide: oxidized) having a layer thickness of 0.04 μm. Cerium = 1: 4) and a three-layer structure of a shell layer (cerium oxide) having a layer thickness of 0.01 μm.

  The abrasive particles 11 are monodisperse particles having an average particle diameter of 0.70 μm and a coefficient of variation of 15%, a core layer (tungsten oxide) of 0.52 μm, and an intermediate layer (tungsten oxide: cerium oxide = 0.08 μm). 1: 4) and a three-layer structure of a shell layer (cerium oxide) having a layer thickness of 0.01 μm.

≪Preparation of abrasive slurry≫
<Preparation of abrasive slurry 1>
125 g of abrasive particles 1 and 2.2 g of an aqueous ammonium polyacrylate salt solution (40% by mass) having a weight average molecular weight of 5000 as a dispersant and 2372 g of deionized water were mixed and subjected to ultrasonic dispersion while stirring. . Dispersion was performed with an ultrasonic frequency of 40 kHz and a dispersion time of 10 minutes. The obtained slurry was filtered through a 0.8 micron filter, and deionized water was further added to prepare an abrasive slurry 1 having an abrasive particle 1 content of 2 mass%. The pH (25 ° C.) of the abrasive slurry 1 was 7.7.

<Preparation of abrasive slurry 2-11>
In the preparation of the abrasive slurry 1, abrasive slurries 2 to 11 were prepared in the same manner except that the abrasive particles 1 were changed to the abrasive particles 2 to 11.
Table 1 shows the pH (25 ° C.) of each abrasive slurry.

≪Preparation of additive liquid≫
After preparing a polyacrylic acid ammonium salt aqueous solution (40 mass%) having a weight average molecular weight of 5000 as an additive, and adjusting this to a concentration shown in Table 1 in deionized water, pH adjustment is performed with a nitric acid aqueous solution, This was used as an additive solution. Table 1 shows the pH (25 ° C.) of the polishing slurry for CMP when the abrasive slurry and the additive solution are mixed.
In addition, the polyacrylic acid ammonium salt was not added to the additive liquid used for CMP polishing liquid 119, and pH adjustment with nitric acid was not performed in the additive liquid used for CMP polishing liquid 120.

≪Evaluation≫
The abrasive slurries 1 to 11 and the additive liquid prepared as described above were used in the combinations shown in Table 1 (CMP polishing liquids 101 to 125), and the following evaluations were performed.

<Evaluation of polishing rate>
A substrate is mounted on a surface plate on which a polishing pad (Rodel Nitta Co., Ltd .; product name “IC1000 / Suba400”) of a two-layer type polishing apparatus (product name “PM5”) of a polishing apparatus (Product name “PM5”) is attached. A silicon wafer with a diameter of 125 mm on which a silicon oxide film produced by TEOS-plasma CVD method is set in a holder with a suction pad for use is set with the insulating film face down so that the polishing load is 300 g / cm ^2. I put a weight on it. Abrasive slurry (solid content: 5% by mass) and additive liquid are fed at a rate of 25 ml / min each on the surface plate in the combination shown in Table 1, and the nozzle is adjusted so that it becomes one liquid immediately before the surface plate. While dropping, the surface plate was rotated at 40 rpm for 2 minutes to polish the insulating film.
After polishing, the wafer was removed from the holder, washed thoroughly with running water, and then further washed with an ultrasonic cleaner for 20 minutes. After washing, water droplets were removed with a spin dryer and dried for 10 minutes with a 120 ° C. dryer. Using an optical interference type film thickness measuring device (manufactured by Chino Corporation: product name “IRM8599B”), the change in film thickness before and after polishing was measured, and the polishing rate was calculated.
The results are shown in Table 2.

Similarly, a silicon nitride film produced by low-pressure CVD instead of a silicon oxide film produced by TEOS-plasma CVD was polished under the same conditions, the change in film thickness before and after polishing was measured, and the polishing rate was calculated. From the results of film thickness measurement, it was found that the silicon oxide film produced by the TEOS-plasma CVD method and the silicon nitride film produced by the low pressure CVD method had a uniform thickness over the entire surface of the wafer.
The results are shown in Table 2.

<Evaluation of polishing scratches>
The surface of the insulating film was not scratched by visual observation under a mercury lamp light source, but was further observed in detail with a wafer appearance inspection device (manufactured by Olympus Corporation: product name “Olympus AL-2000”).
The results are shown in Table 2.

<Evaluation of flatness (dishing)>
Similarly, a silicon oxide film in which convex portions having a height of 5000 μm and a height of 5000 μm are formed at intervals of 100 μm is polished, and the amount of dent (dishing) between the convex portion and the concave portion when the convex portion is polished is scanned. The flatness was evaluated using a scanning probe microscope (manufactured by Seiko Instruments Inc .: product name “SPI3800N / SPA400”).
The results are shown in Table 2.

<Evaluation of detergency>
Similar to the evaluation of the polishing rate, after polishing the silicon oxide film prepared by TEOS-plasma CVD method and the silicon nitride film prepared by low pressure CVD method, samples were extracted from each polished surface and analyzed by ICP (detection limit) 3 × 10 ⁸ / cm ² ), the amount of residual cerium (number of atoms) was evaluated.
The results are shown in Table 2.

<Summary>
As is apparent from Table 2, the polishing liquids 101 to 118 for CMP of the present invention were compared with the polishing liquids for polishing CMP 119 to 125 of the comparative example and the polishing rate of the silicon oxide film and the silicon oxide film and the silicon nitride film. The polishing rate ratio, polishing scratches, flatness and cleanability were excellent.
From the above, particles having a core-shell structure, and the core layer includes Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, In, Sn, The shell layer contains an oxide of at least one element selected from Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, W, Bi, Th, and an alkaline earth metal, It can be seen that the CMP polishing liquid using abrasive particles containing cerium oxide is useful for suppressing polishing scratches and dishing and obtaining a higher polishing rate and cleaning performance.

2 Core layer 4 Shell layer 6 Intermediate layer 8 Composite layers 10 and 20 Abrasive particles

Claims (3)

An abrasive slurry containing an abrasive, a dispersant and water, and an additive containing a carboxylic acid or a water-soluble organic polymer having a carboxylate group, an inorganic acid or an inorganic acid salt and water are mixed during polishing. A CMP polishing liquid used for polishing a film to be polished,
The abrasive particles used for the abrasive are particles having a core / shell structure,
The core layer includes aluminum (Al), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), Copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), indium (In), tin (Sn), yttrium (Y), gatrinium (Gd), terbium (Tb), From dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), tungsten (W), bismuth (Bi), thorium (Th) and alkaline earth metals Contains an oxide of at least one element selected, and
A polishing slurry for CMP, wherein the shell layer contains cerium oxide.   The CMP polishing liquid has a pH of 3 to 6 at 25 ° C., and the total concentration of the water-soluble organic polymer having a carboxylic acid group or a carboxylic acid group is 0.01 to 0 based on the total mass of the polishing liquid. The polishing liquid for CMP according to claim 1, wherein the polishing liquid is in the range of 0.5 mass%. Further comprising an intermediate layer between the core layer and the shell layer; and
The intermediate layer includes aluminum (Al), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), and nickel (Ni). , Copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), indium (In), tin (Sn), yttrium (Y), gatrinium (Gd), terbium (Tb) , Dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), tungsten (W), bismuth (Bi), thorium (Th) and alkaline earth metals The oxide of at least 1 sort (s) chosen from these, and cerium oxide are contained, The claim 1 or Claim characterized by the above-mentioned CMP polishing slurry according to 2.

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