JP2016096230A - Semiconductor element manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor element manufacturing method having a polishing process excellent in polishing speed and washability.SOLUTION: A semiconductor element manufacturing method of the present embodiment is a semiconductor element manufacturing method of performing polishing by using a polishing agent slurry containing polishing agent particles which includes mixed crystal of two and more kinds of metal oxides. One kind of the metal oxide is cerium oxide within a range of 50-90 mol% with respect to the polishing agent particles; and the other kind of the metal oxide is at least one selected from yttrium oxide, gadolinium oxide, lanthanum oxide, iron oxide and manganese oxide within a range of 5-50 mol%; and a total sum of the metal oxides is 90 mol% and over. The semiconductor element manufacturing method further comprises: a polishing process of performing polishing by using the polishing agent slurry adjusted to be alkaline; and a washing process of performing washing by using a wash solution adjusted to be acid.SELECTED DRAWING: None

Description

  The present invention relates to a method for manufacturing a semiconductor device. More specifically, the present invention relates to a method for manufacturing a semiconductor element having a polishing step with excellent polishing rate and cleanability.

  Semiconductor devices represented by silicon semiconductors have made remarkable progress in miniaturization and high integration in accordance with market needs such as high performance and miniaturization. For this reason, an advanced planarization technique for producing a fine wiring pattern is indispensable, and a chemical mechanical polishing (CMP) for polishing a wafer surface with an abrasive slurry containing an abrasive in a manufacturing process of a semiconductor element. Polishing) process has been introduced.

  However, in this chemical mechanical polishing process (hereinafter also referred to as CMP process), polishing fine particles and the like in the abrasive slurry remain on the polished wafer and lead to defective semiconductor elements. There was a need to remove things. In particular, when improving the polishing rate of the oxide film in order to improve the throughput, it is necessary to increase the adsorbing power of the abrasive particles to the polishing target film in the CMP process. There is a problem that abrasive particles tend to remain on the surface.

  As a cleaning method for removing the abrasive particles remaining on the surface of the oxide film of the object to be polished, there is a method of controlling the zeta potential so that the abrasive particles are aggregated and easily removed by brush scrub cleaning (see Patent Document 1). Although proposed, the cleanability was not sufficient. In addition, a method of dissolving the particles themselves (see Patent Document 2) has also been proposed. However, when the particle diameter is controlled to be small so as to be easily dissolved in an acid, the polishing rate is affected, and both the polishing rate and the cleaning property are compatible. The point was not enough.

JP-A-9-22885 JP 2001-206737 A

  The present invention has been made in view of the above problems and circumstances, and a problem to be solved is to provide a method for manufacturing a semiconductor element having a polishing step excellent in polishing rate and cleanability.

  In order to solve the above-mentioned problems, the present inventor uses abrasive particles containing a mixed crystal of cerium oxide and a specific metal oxide dissolved in an acid in the process of studying the cause of the above-mentioned problem, and makes it alkaline. It has been found that the polishing performance of the object to be polished is greatly improved by polishing with the adjusted abrasive slurry and washing with an acid, and the present invention has been achieved.

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

  1.2 A method for producing a semiconductor device for polishing using an abrasive slurry containing abrasive particles containing a mixed crystal of metal oxides of at least one kind, wherein one of the metal oxides is converted into abrasive particles On the other hand, it is cerium oxide in the range of 50 to 90 mol%, and the other metal oxide is selected from yttrium oxide, gadolinium oxide, lanthanum oxide, iron oxide or manganese oxide in the range of 5 to 50 mol%. A polishing step of at least one kind of metal oxide and the total of these metal oxides being 90 mol% or more, and polishing using an abrasive slurry adjusted to be alkaline, and adjusted to be acidic And a cleaning step of cleaning using the cleaning liquid.

  2. The abrasive slurry has a pH value in terms of 25 ° C. of 8.0 to 14.0, and the cleaning solution has a pH value in terms of 25 ° C. of 0.0 to 5.0. 2. A method of manufacturing a semiconductor device according to item 1, wherein:

  3. 3. The method for manufacturing a semiconductor element according to claim 1 or 2, wherein an average particle diameter of the abrasive particles is in a range of 50 to 300 nm.

  4). The method for manufacturing a semiconductor device according to any one of claims 1 to 3, wherein the abrasive particles are in a spherical monodisperse form.

  5. The semiconductor according to any one of Items 1 to 4, wherein a pH value in terms of 25 ° C. of the acidic cleaning solution is in a range of 0.0 to 4.0. Device manufacturing method.

  By the above means of the present invention, it is possible to provide a method for manufacturing a semiconductor element having a polishing step excellent in polishing rate and cleanability.

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

  As described above, in order to improve the polishing rate, in the CMP process, it is necessary to increase the adsorptive power of the abrasive particles with respect to the film to be polished. For this reason, the abrasive particles on the surface of the film to be polished are washed. Etc. are likely to remain.

  As a countermeasure, when removing particles from the surface of the film to be polished by adjusting the pH of the cleaning solution to the weak acid side and dissolving part of the particles to lower the adsorption power, the particles once removed have a smaller particle size. It becomes easy to re-adhere, and the cleaning effect does not increase.

  FIG. 1 shows a conceptual diagram of the mechanism when the abrasive particles easily reattach. The abrasive particles 1 (FIG. 1 (a)) attached to the polishing target film 2 are partially dissolved under acidic conditions (FIG. 1 (b)), and the acid-dissolved portion 3 is removed. Small abrasive particles 4 are obtained. However, it is considered that it easily adheres to the surface of the film 2 to be polished again due to the influence of van der Waals force (FIG. 1C).

  FIG. 2 shows a conceptual diagram of the mechanism according to the present invention when the abrasive particles are difficult to reattach. By using abrasive particles composed of two or more kinds of metal oxides randomly and uniformly mixed as crystallites as abrasive particles, one metal oxide is easily dissolved under acidic conditions. be able to. The abrasive particles 1 attached to the polishing target film 2 (FIG. 1 (a)) use an abrasive slurry adjusted to be alkaline at the time of polishing, and use a cleaning liquid adjusted to be acidic at the time of cleaning. The metal oxide on one side is melted to form abrasive particles 5 from which the acid-soluble portion 3 has been removed (FIG. 2B). For this reason, the adsorptive power of the abrasive particles 5 to the polishing target film 2 is weakened, and the abrasive particles 5 can be easily separated from the polishing target film 2, thereby improving the cleaning performance. Further, since the particle diameter does not become small, it is considered that it is difficult to reattach (FIG. 2C).

Conceptual diagram of the mechanism when abrasive particles tend to reattach Conceptual diagram of the mechanism when abrasive particles are difficult to reattach Conceptual diagram showing an example of flattening processing

  A method for manufacturing a semiconductor element of the present invention is a method for manufacturing a semiconductor element, wherein polishing is performed using an abrasive slurry containing abrasive particles containing a mixed crystal of two or more kinds of metal oxides. One type is cerium oxide in the range of 50 to 90 mol% with respect to the abrasive particles, and the other metal oxide is in the range of 5 to 50 mol%, yttrium oxide, gadolinium oxide, lanthanum oxide, Polishing is performed using an abrasive slurry that is at least one metal oxide selected from iron oxide or manganese oxide, the total of these metal oxides is 90 mol% or more, and is adjusted to be alkaline. It has a grinding | polishing process and the washing | cleaning process wash | cleaned using the washing | cleaning liquid adjusted to acidity. This feature is a technical feature common to the inventions according to claims 1 to 5.

  As an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, the pH value of the abrasive slurry in terms of 25 ° C. is in the range of 8.0 to 14.0, and the pH of the cleaning liquid in terms of 25 ° C. The value is preferably in the range of 0.0 to 5.0. In addition, it is preferable that the average particle diameter of the abrasive particles is in the range of 50 to 300 nm because the semiconductor element is hardly damaged while ensuring sufficient polishing properties. Furthermore, it is preferable that the abrasive particles are in a spherical monodisperse form in order to prevent scratches and to perform high-speed polishing and to make the dissolution rate in the cleaning step B uniform among the abrasive particles.

  Furthermore, in this invention, it is preferable that the pH value of 25 degreeC conversion of the washing | cleaning liquid adjusted to acidity exists in the range of 0.0-4.0. Thereby, a high cleaning effect is obtained.

  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, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<< Semiconductor Device Manufacturing Method >>
A method for manufacturing a semiconductor element of the present invention is a method for manufacturing a semiconductor element, wherein polishing is performed using an abrasive slurry containing abrasive particles containing a mixed crystal of two or more kinds of metal oxides. One type is cerium oxide in the range of 50 to 90 mol% with respect to the abrasive particles, and the other metal oxide is in the range of 5 to 50 mol%, yttrium oxide, gadolinium oxide, lanthanum oxide, Polishing is performed using an abrasive slurry that is at least one metal oxide selected from iron oxide or manganese oxide, the total of these metal oxides is 90 mol% or more, and is adjusted to be alkaline. It has a grinding | polishing process and the washing | cleaning process wash | cleaned using the washing | cleaning liquid adjusted to acidity.

  In general, a semiconductor element uses a silicon wafer on which an oxide film and a nitride film are formed, and (1) a pattern formation process, (2) an element isolation formation process, (3) a gate formation process, (4) a wiring formation process, ( 5) Manufactured through a wafer inspection process and (6) an assembly process.

  The present invention is applied to a polishing step in a semiconductor element manufacturing process. Specifically, (2) a polishing step after embedding an insulating film in the element isolation forming step, (3) a polishing step after forming the interlayer insulating film in the gate forming step, and (4) a buried insulating in the wiring forming step. The present invention can be applied to a film polishing process.

  In the present invention, the polishing step includes at least a polishing step for polishing using an abrasive slurry adjusted to be alkaline, and a cleaning step for cleaning using an acidic cleaning solution.

  FIG. 3 is a conceptual diagram illustrating an example of a planarization process in the polishing process. 3A and 3B show an example of the planarization process of the interlayer insulating film. The upper surface portion (FIG. 3A) of the interlayer insulating film 7 covering the silicon substrate 6 is polished to flatten the polished surface 8 (FIG. 3B). 3C and 3B, the insulating film 10 (FIG. 3C) embedded in the silicon substrate 9 is polished to flatten the polished surface 8 (FIG. 3D).

  The present invention is characterized by a polishing process, and a known method can be applied to the manufacturing process of other semiconductor elements.

《Polishing process》
The polishing step applied to the method for manufacturing a semiconductor device of the present invention includes cerium oxide in the range of 50 to 90 mol%, yttrium oxide, gadolinium oxide, lanthanum oxide, and iron oxide in the range of 5 to 50 mol%. Or polishing using an abrasive slurry containing abrasive particles containing at least one metal oxide selected from manganese oxide, and polishing using at least an abrasive slurry adjusted to be alkaline (hereinafter referred to as a polishing step) And a cleaning step (hereinafter also referred to as a cleaning step B) for cleaning using a cleaning liquid adjusted to be acidic.

  The polishing step preferably has six steps: [1] loading, [2] polishing step A, [3] cleaning step B, [4] water cleaning, [5] drying and [6] removal.

[1] Loading In this process, the object to be polished is attached to the polishing head, and the object to be polished is loaded on the lower surface plate of the polishing machine to which the polishing pad (polishing cloth) is attached. The CMP polishing machine is not particularly limited, but the cleaning step B is attached, and it is preferable to clean immediately after the polishing step A from the viewpoint of cleaning properties.

[2] Polishing step for polishing using an alkaline slurry adjusted to be alkaline In a polishing step (polishing step A) for polishing using an alkaline slurry adjusted to be alkaline, an abrasive slurry adjusted to be alkaline is used. This is a step of polishing the object to be polished.

As a polishing apparatus, a general polishing apparatus having a holder for holding a semiconductor substrate and a surface plate to which a polishing cloth (pad) is attached (a motor or the like whose rotation speed can be changed) is attached. As an abrasive cloth, a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used, and there is no restriction | limiting in particular. Further, it is preferable that the polishing cloth is subjected to groove processing so that the abrasive slurry is accumulated. 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. 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.

(Abrasive slurry adjusted to alkalinity)
In the present invention, the abrasive slurry is adjusted to be alkaline. By adding an alkali agent to water containing abrasive powder containing abrasive particles described later, an abrasive slurry adjusted to be alkaline can be prepared. By adding a dispersant or the like to the abrasive slurry, aggregation is prevented, and the slurry is constantly stirred using a stirrer or the like to maintain a dispersed state. The abrasive slurry is supplied to the polishing machine using a supply pump.

  The pH value of the abrasive slurry used in the present invention is not particularly limited as long as it can be adjusted to be alkaline. The pH value of the abrasive slurry is measured as a pH value in terms of 25 ° C. Preferably, the abrasive slurry has a pH value in terms of 25 ° C. in the range of 8.0 to 14.0. By making the abrasive slurry alkaline, it is possible to obtain an abrasive slurry containing cerium oxide and having a high polishing rate. By adjusting the addition amount, it is possible to obtain an abrasive slurry having a desired pH value.

  The density | concentration of an abrasive can be 0.5-3.0 mass% with respect to water.

  Examples of the method for adjusting the abrasive slurry to be alkaline include a method of adding an alkaline agent dissolved in the abrasive slurry. Examples of the alkaline agent include alkali metal hydroxides such as sodium hydroxide, ammonium hydroxide, potassium hydroxide and lithium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide. Inorganic alkali agents; monomethylamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, DBU (1,8-diazabicyclo [5,4,0] -7-undecene), DBN (1,5-diazabicyclo [ 4,3,0] -5-nonene), tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, triethylbutylammonium hydroxide, etc. And the like to apply. Of these, sodium hydroxide and potassium hydroxide are preferable. These alkali agents can be used alone or in combination of two or more.

  The solvent is preferably water, but other solvents other than water can be added as long as the effects of the present invention are not impaired.

  A surfactant can be added as a dispersant to the abrasive slurry. For example, examples of the surfactant include an anionic surfactant, a cationic surfactant, a nonionic surfactant, and a zwitterionic surfactant. These may be used alone or in combination of two or more. It may be used. Of these, anionic surfactants and nonionic surfactants are preferred in the present invention.

  Moreover, additives, such as a thickener, can also be added as needed.

[3] Cleaning step for cleaning with an acid-adjusted cleaning solution In the cleaning step (cleaning step B) for cleaning with an acid-adjusted cleaning solution, a step of removing abrasive particles and the like adhering to the object to be polished It is. In this step, at least one metal oxide selected from yttrium oxide, gadolinium oxide, lanthanum oxide, iron oxide or manganese oxide contained in the abrasive particles is used by using an acid-adjusted cleaning solution. Abrasive particles are removed from the object to be polished by dissolving and removing oxides and the like.

  The pH value of the cleaning solution is measured at a pH converted to 25 ° C. Preferably, the pH value in terms of 25 ° C. is in the range of 0.0 to 5.0.

  As the cleaning liquid adjusted to be acidic, an aqueous solution of an acid compound can be used. For example, examples of the acid compound include sulfuric acid, hydrochloric acid, carbonic acid, perchloric acid, phosphoric acid, nitric acid, and hydrogen fluoride. Examples of the organic acid include acetic acid, oxalic acid, citric acid, p-toluenesulfonic acid and the like. It is preferable to use an inorganic acid for convenience and the like. Of the inorganic acids, hydrogen fluoride is preferred for reasons of cleanability.

[4] Washing with water In order to remove the cleaning solution adjusted to be acidic in the cleaning step B, it is preferable to wash with water so that no acid component remains on the surface. By removing the acid component, the surface of the object to be polished is not roughened by the acid, and the integrated density of the semiconductor is not affected.

[5] Drying After washing with water, dry. It can be dried according to a conventional method such as blowing warm air.

[6] Removal After that, it is removed from the polishing machine, and the polishing process is completed.

[Abrasive particles]
The abrasive particles according to the present invention are abrasive particles containing a mixed crystal of two or more kinds of metal oxides, and one kind of the metal oxide is in the range of 50 to 90 mol% with respect to the abrasive particles. Cerium oxide, and the other metal oxide is at least one metal oxide selected from yttrium oxide, gadolinium oxide, lanthanum oxide, iron oxide or manganese oxide in the range of 5 to 50 mol%, And the sum total of these metal oxides is 90 mol% or more.

(Abrasive particle composition)
The content of cerium oxide is in the range of 50 to 90 mol% with respect to the abrasive particles. From the viewpoint of ensuring the polishing rate, the polishing rate of cerium oxide is preferably in the range of 70 to 90 mol%. If this content is less than 50%, the polishing rate is lowered, which is not preferable. Moreover, when content rate exceeds 90%, since the content rate of the other metal oxide melt | dissolved in an acidic washing | cleaning process falls and cleaning property is inferior, it is unpreferable.

  The metal oxide other than cerium oxide is at least one metal oxide selected from yttrium oxide, gadolinium oxide, lanthanum oxide, iron oxide or manganese oxide in the range of 5 to 50 mol%. These metal oxides have a property of being dissolved relatively easily in an acidic solution, and in the acidic cleaning step described later, a part of the abrasive particles is dissolved, so that the cleaning property is remarkably improved. When the content of the metal oxide in the abrasive particles is less than 5 mol%, the solubility of the abrasive particles becomes insufficient and the cleaning properties deteriorate. In addition, when the content in the abrasive particles exceeds 50 mol%, the cerium oxide content decreases and the polishing rate deteriorates, which is not preferable. Further, cerium oxide is 50 to 90 mol%, and other metal oxides such as yttrium oxide, gadonium oxide, lanthanum oxide, iron oxide or manganese oxide are 5 to 50%, and their total is 90 mol. If it is% or more, other substances may be contained in a proportion of 0 to 10%.

  In addition, it is preferable that the abrasive particles are in a spherical monodisperse form in order to prevent scratches and to perform high-speed polishing, and to make the dissolution rate in the cleaning step B uniform among the abrasive particles.

  The metal oxide according to the present invention is polished to be cerium (IV) oxide, yttrium oxide (III), gadolinium (III) oxide, lanthanum oxide (III), iron (III) oxide or manganese (III) oxide. It is preferable from the viewpoint of speed.

(Method for producing abrasive particles)
The abrasive particles according to the present invention are at least selected from cerium oxide in the range of 50 to 90 mol% and yttrium oxide, gadolinium oxide, lanthanum oxide, iron oxide or manganese oxide in the range of 5 to 50 mol%. This is an abrasive particle containing a mixed crystal of one kind of metal oxide. The abrasive particles are preferably spherical monodisperse.

  By using spherical monodispersed abrasive particles containing cerium oxide in the range of 50 to 90 mol% with respect to the abrasive particles, the surface to be polished is hardly scratched and polished at a high polishing rate. be able to.

  In order to produce such spherical monodispersed abrasive particles, a cerium-containing compound such that cerium oxide is in the range of 50 to 90 mol% and other metal oxides in the range of 5 to 50 mol%. As described above, ureas are contained in an aqueous solution (hereinafter also referred to as a metal salt aqueous solution) containing at least one metal selected from yttrium, gadolinium, lanthanum, iron, or manganese, and the total of them is 90% or more. It is preferable to prepare abrasive particles by adding an aqueous solution or a thermally decomposed urea aqueous solution. By such a manufacturing method, a mixed crystal of cerium oxide and a metal oxide of another metal can be easily produced. Other substances of 0 to 10% may be added to the aqueous metal salt solution.

  In particular, a metal in which 0 to 10% of other substances are added in an aqueous solution (metal salt aqueous solution) of a compound containing at least one metal selected from cerium-containing compounds and yttrium, gadolinium, lanthanum, iron or manganese Reaction in a step of forming an abrasive precursor particle by adding an aqueous urea solution to a salt aqueous solution and a step of firing the abrasive precursor particle and forming the abrasive precursor particle In the initial particle nucleation process, the thermally decomposed urea aqueous solution is added, and in the particle growth process after the nucleation process, the urea aqueous solution or the thermally decomposed urea aqueous solution is added to produce abrasive particles. It is preferable.

  Spherical monodispersed abrasive particles are obtained by firing abrasive precursor particles generated in a reaction solution by mixing and heating a metal aqueous solution and a urea aqueous solution. The reaction liquid refers to a liquid obtained by mixing a metal salt aqueous solution and a urea aqueous solution.

The method for producing spherical abrasive particles has at least a step of adding an aqueous urea solution in an aqueous metal salt solution to form abrasive precursor particles and a step of firing the abrasive precursor particles, It is preferable to consist of these five steps. 1. 1. Aqueous urea preparation step A. 2. Metal salt aqueous solution preparation step B Step C for forming abrasive precursor particles, 4. Solid-liquid separation step D, 5. Firing step E
1. Aqueous urea preparation step A
The urea aqueous solution preparation step A is a step of preparing a urea aqueous solution having a predetermined concentration, or preparing an aqueous urea solution decomposed to be added by heating in an airtight container.

  For example, by heating an aqueous urea solution in a hermetically sealed container, hydrolysis can proceed while retaining the solvent. Thereby, in addition to the carbon dioxide and ammonia produced by the hydrolysis of urea, the three components of urea are dissolved in the urea aqueous solution.

  Carbon dioxide exists as carbonate ions in the solution and becomes a raw material for abrasive precursor particles, which are basic carbonates described later.

  The “thermally decomposed urea aqueous solution” refers to an aqueous urea solution containing carbonate ions as a result of hydrolysis of urea by heating. The degree of hydrolysis can be controlled by the temperature and time of heating in the sealed container. Such an aqueous solution in which ureas are hydrolyzed and contains carbonate ions is also referred to as “decomposed urea liquid”.

  As ureas, in addition to urea, urea salts (for example, nitrates, hydrochlorides, etc.), N, N′-dimethylacetylurea, N, N′-dibenzoylurea, benzenesulfonylurea, p-toluenesulfonylurea, Examples thereof include trimethylurea, tetraethylurea, tetramethylurea, triphenylurea, tetraphenylurea, N-benzoylurea, methylisourea, ethylisourea, ammonium carbonate, and ammonium bicarbonate. Of these, urea is preferred. In addition, in the following Examples, although it shows about the case where basic carbonate is formed using urea aqueous solution, it is an example and it is not limited to this.

  The carbonate ion concentration in the decomposed urea solution is a value measured at room temperature (25 ° C.). The carbonate ion concentration can be measured by an ion chromatography method. For example, it can be measured using an ion chromatograph manufactured by DIONEX, DX500 or the like.

2. Metal salt aqueous solution preparation process B
The metal salt aqueous solution preparation step B is a step of preparing an aqueous solution (metal salt aqueous solution) of a compound containing a cerium-containing compound and at least one metal selected from yttrium, gadolinium, lanthanum, iron or manganese and other substances. It is.

  Specifically, the aqueous metal salt solution contains 50 to 90 mol% of cerium, and the total content of at least one metal selected from yttrium, gadolinium, lanthanum, iron or manganese is 5 to 50 mol%. It is preferable to prepare an aqueous solution having a composition that falls within the range and contains 0 to 10% of other substances.

  The ion concentration of these liquids in the aqueous solution is 0.001 to 50 mol / L, and ureas are preferably 5 to 50 times the ion concentration.

  As salts of these elements that can be used for preparing the aqueous solution, nitrates, hydrochlorides, sulfates and the like can be used, but it is preferable to use nitrates. Thereby, an abrasive with few impurities can be manufactured.

3. Process C for forming abrasive precursor particles
Step C of forming the abrasive precursor particles is a step of forming the abrasive precursor particles by adding an aqueous urea solution to the aqueous metal salt solution.

  In step C of forming abrasive precursor particles, an aqueous solution of urea that is thermally decomposed in the nucleation process of particles at the initial stage of the reaction is added to an aqueous solution of metal salt, and an aqueous solution of ureas or Add thermally decomposed urea aqueous solution.

(I) Nucleation process In the nucleation process, a decomposed urea solution is added to a heated metal salt aqueous solution capable of hydrolyzing ureas. Nucleation can be carried out in a short time by adding a decomposed urea solution containing a large amount of carbonate ions as a raw material in the nucleation process of particles at the initial stage of the reaction for forming the abrasive precursor particles. . For this reason, it is considered that the particle size distribution of the produced nuclei can be made narrower than before, compared with the case where the abrasive precursor particles are formed by mixing the conventional aqueous metal salt solution and the decomposed urea solution and then heating. .

  The size of the nucleus is preferably about 10 to 300 nm. It can be carried out by appropriately controlling the concentration of the aqueous metal salt solution and the decomposed urea solution, the reaction temperature, the degree of decomposition of the decomposed urea solution, the addition rate and the added amount of the decomposed urea solution. The formation of nuclei can be confirmed from the fact that the reaction solution is colored or cloudy from blue to white. When the particle size is small, it is observed in blue, and as it increases, it is observed in white.

  The addition rate of the thermally decomposed aqueous urea solution added in the nucleation process is preferably within a range of 0.01 to 50 mol per minute with respect to 1 L of the reaction solution in terms of the urea concentration before the thermal decomposition. . More preferably, the addition rate is in the range of 0.10 to 30 mol.

  When the addition rate is shorter, the particle size distribution of the produced nuclei becomes narrower, but when it is too early, the produced nuclei aggregate or the local concentration distribution becomes larger, so the nuclei grow anisotropically, and the particle size distribution of the nuclei. This is because may increase.

  The addition time is preferably within 10 minutes. More preferably, it is within 5 minutes. More preferably, it is within 1 minute.

  The temperature of the reaction solution in which the aqueous metal salt solution and the decomposed urea solution are mixed is preferably a temperature at which ureas can be hydrolyzed. Specifically, the temperature of the reaction solution is 75 to 100 ° C, preferably 80 to 100 ° C, more preferably 90 to 100 ° C.

(Ii) Particle Growth Process The particle growth process is a process of growing the core particles formed in the nucleation process into larger abrasive precursor particles. The grain growth process takes place after the nucleation process. After the addition of the decomposed urea aqueous solution added in the nucleation process, after the reaction solution turns blue to white or becomes cloudy, the particle growth process is started by adding the urea aqueous solution or the thermally decomposed urea aqueous solution. .

  Specifically, after completing the addition of the decomposed urea aqueous solution, after confirming that the reaction solution is colored or turbid from blue to white, within about 10 minutes, the urea aqueous solution prepared in the urea aqueous solution preparation step A or The thermally decomposed urea aqueous solution is added to the metal salt aqueous solution prepared in the metal salt aqueous solution preparation step B. The mixed solution is stirred while heating. By mixing the urea aqueous solution and the metal salt aqueous solution, the core of the abrasive grows and a precursor of abrasive particles is obtained.

  The concentration of the aqueous urea solution added in the growth process is preferably in the range of 0.05 to 10 mol / L.

  Further, the carbonate ion concentration of the thermally decomposed aqueous urea solution added during the particle growth process is within the range of 0.01 to 30 mol / L, so that the particle size distribution of the growing abrasive precursor particles is not increased. It is preferable from the viewpoint.

  The temperature of the reaction solution in which the metal salt aqueous solution and the decomposed urea aqueous solution are mixed is preferably a temperature at which ureas can be hydrolyzed. Specifically, the temperature of the reaction solution is 75 to 100 ° C, preferably 80 to 100 ° C, more preferably 90 to 100 ° C.

  In the case of heating and stirring in the step of forming abrasive precursor particles, the shape of the stirrer is not particularly specified as long as sufficient stirring efficiency is obtained, but in order to obtain higher stirring efficiency, the rotor It is preferable to use a stator type stirrer.

4). Solid-liquid separation process D
After heating and stirring, solid-liquid separation is performed to separate the generated precipitate (precursor of abrasive fine particles) from the solution. The solid-liquid separation method may be a general method. For example, a precursor of abrasive particles can be obtained by filtration using a filter or the like.

5). Firing step E
In the firing step E (also referred to as a firing step), the precursor of the abrasive particles obtained in the solid-liquid separation step D is fired at 400 ° C. or higher in air or in an oxidizing atmosphere. The precursor of the baked abrasive particle becomes an oxide and becomes an abrasive particle containing cerium oxide.

  By cooling after firing, the abrasive particles can be stabilized and then recovered as an abrasive containing the abrasive particles.

  By producing an abrasive using the abrasive production method, an abrasive containing spherical abrasive particles that hardly contains anisotropically grown abrasive particles can be obtained.

  The polishing rate can be measured by, for example, circulating the abrasive slurry to a polishing machine and performing polishing. The thickness before and after polishing is measured by Nikon Digimicro (MF501), and the polishing amount (μm) per minute can be calculated from the thickness displacement to obtain the polishing rate.

  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 "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

[Example 1]
<< Manufacture of abrasive particles 1 >>
The abrasive particles 1 according to the present invention were produced by the following procedure.
(1) 0.5 L of 5.0 mol / L urea aqueous solution B1 was prepared.
(2) Pure water was added to 200 mL of a 1.0 mol / L cerium nitrate aqueous solution to make 9.0 L.
(3) The cerium nitrate aqueous solution prepared in (2) above was heated to 90 ° C.
(4) The decomposed urea aqueous solution prepared in (1) was added to the cerium nitrate aqueous solution heated in (3) above, and heated and stirred for 10 minutes (nucleation process).
(5) 0.5 L of an aqueous urea solution having a concentration of 0.05 mol / L was added to the mixed solution of (4) above, and the mixture was heated and stirred until a desired particle size was obtained. At that time, the solution was taken out every 5 minutes, and the particle diameter was confirmed. For confirmation of the particle diameter, a laser diffraction / scattering particle size distribution analyzer LA-920 was used.
(6) The precursor of the abrasive particles precipitated in the mixed solution heated and stirred in the above (5) was separated by a membrane filter.
(7) The abrasive particle precursors separated in (6) above were fired at 600 ° C. to obtain abrasive particles 1.

(Preparation of aqueous urea solution B1)
0.5 L of 10 mol / L urea aqueous solution was prepared, and it heated at 100 degreeC for 6 hours within the airtight container. Thereafter, the urea aqueous solution was cooled to room temperature (25 ° C.) to obtain a urea aqueous solution of B1. The carbonate ion concentration measured at room temperature (25 ° C.) was 12 mmol / L.

<Production of abrasive particles 2 to 4 and 9 to 30>
In the production of the abrasive particles 1, instead of the cerium nitrate aqueous solution, the same concentration of nitric acid aqueous solution of yttrium, gadolinium, lanthanum, iron, manganese or calcium was used, respectively, and the total amount was changed as shown in Tables 2 and 3. Abrasive particles 2 to 4 and 9 to 30 were prepared using a nitrate aqueous solution so that the ratio was%.

<Production of abrasive particles 5-8>
(1) 1.0 L of 2.5 mol / L urea aqueous solution was prepared.
(2) After mixing 180 mL of 1.0 mol / L cerium nitrate aqueous solution and 20 mL of 1.0 mol / L yttrium nitrate aqueous solution, pure water was added to make 9.0 L.
(3) The urea aqueous solution prepared in the procedure (1) was added to the cerium nitrate aqueous solution prepared in the procedure (2) and stirred for 10 minutes.
(4) The mixed solution stirred in the procedure (3) was heated to 90 ° C. and stirred until a desired particle size was obtained. At that time, the solution was taken out every 5 minutes, and the particle diameter was confirmed. For confirmation of the particle diameter, a laser diffraction / scattering particle size distribution analyzer LA-920 was used.
(5) The precursor of the abrasive particles precipitated in the mixed solution heated and stirred in the procedure (4) was separated by a membrane filter.
(6) Abrasive particle precursors separated in step (5) were fired at 600 ° C. to produce abrasive particles 5 to 8.

  The metal oxides according to the present invention were cerium (IV) oxide, yttrium oxide (III), gadolinium (III) oxide, lanthanum oxide (III), iron (III) oxide, and manganese (III) oxide, respectively.

<Evaluation of abrasive particles>
About the abrasive | polishing material particles 1-30, the composition, the shape, and polishing performance were evaluated in accordance with the following method.

1. Elemental Analysis 1 g of each of the obtained abrasive particles 1 to 30 is dissolved in a mixed solution of 10 ml of nitric acid aqueous solution and 1.0 ml of hydrogen peroxide solution, and ICP emission spectroscopic plasma apparatus (ICP-AES) manufactured by SII Nano Technology Co., Ltd. Was used for elemental analysis. The average content of each metal element in the abrasive particles contained in the abrasive was determined as a composition ratio (mol%). As a result, it was found that the values agreed with the prescription values shown in Tables 2 and 3.

2. Particle shape / aspect ratio For abrasive particles, a scanning micrograph (SEM image) was taken, 100 particles were randomly selected, and the major axis was a and the minor axis was b. Was determined as an aspect ratio. In addition, when drawing a circumscribing rectangle for each particle (referred to as “the circumscribing rectangle”), the shortest short side of the circumscribed rectangle is the shortest length, and the longest long side is the length. Is the major axis.

  When the aspect ratio was in the range of 1.00 to 1.15, it was classified as a spherical shape, and when it was outside the range of 1.00 to 1.15, it was classified as indefinite.

  The closer the aspect ratio is to 1, the higher the sphericity. The abrasive containing the abrasive particles according to the present invention having high sphericity is suitable for precision polishing and has a high polishing rate, and is excellent in terms of high productivity.

  As a result of measuring the aspect ratios of the abrasive particles 1 to 30, all of them showed numerical values within 1.10 and confirmed to be spherical.

3. Particle size variation coefficient (CV value)
The coefficient of variation (also referred to as “monodispersity”) of the particle size distribution was determined from a scanning micrograph (SEM image) of 100 abrasive particles, and the monodispersity was evaluated. The particle diameter is determined based on the area of the photographic image of each particle, and the equivalent particle diameter is determined as the particle diameter of each particle. Moreover, the arithmetic average of the particle diameter of each particle was made into the average particle diameter.

  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
In addition, the measurement of the said particle diameter, distribution, etc. can be performed using an image processing measuring device (for example, Luzex AP; Nireco Corporation make). The higher the cerium content of the abrasive particles, the better the polishing rate.

  In the present invention, monodispersion means that the coefficient of variation is within 10%.

  As a result of measuring the aspect ratios of the abrasive particles 1 to 30, it was confirmed that all the variation coefficients showed numerical values within 10%.

  The average particle diameters of the abrasive particles 1 to 30 are shown in Table 2 and Table 3.

[Polishing of silicon wafer 1]
(Preparation of abrasive slurry)
10 g of the abrasive particles 1 and 980 g of deionized water were mixed, and the pH was adjusted to 8.0 (liquid temperature 25 ° C.) with potassium hydroxide while performing ultrasonic dispersion while stirring. The obtained slurry is filtered through a 0.8 micron filter, deionized water is further added, and the pH is adjusted to 8.0 (liquid temperature 25 ° C.) again, whereby an abrasive slurry containing 0.1% by mass of abrasive particles. 1 was obtained.

  The preparation of the abrasive slurry 2 to 36 was carried out in the same manner as the preparation of the abrasive slurry 1 so that the pH value of the abrasive slurry became the values described in Table 2 and Table 3 using each abrasive. . Potassium hydroxide and nitric acid were used as pH adjusters.

(Preparation of cleaning solution)
The pH value of the cleaning solution was adjusted at 25 ° C. using a hydrogen fluoride solution and water as shown in Table 2 and Table 3.

  In the present invention, the pH value was measured using a Lacom Tester desktop pH meter (pH 1500, manufactured by As One Co., Ltd.).

(Polishing process)
The polishing process was performed as follows.

<Polishing of silicon wafer 1>
A substrate on a surface plate on which a polishing pad (manufactured by Logitech Co., Ltd .; product name “PM5”) of a two-layer type semiconductor device polishing pad (manufactured by Nitta Haas; product name “IC1000 / Suba400”) is attached. A silicon wafer with a diameter of 125 mm on which a silicon oxide insulating layer produced by TEOS (tetraethyl orthosilicate) -plasma CVD method is set on a holder to which a suction pad for mounting is attached is set with the insulating layer side down, and the polishing load is 300 g / A weight was applied so as to be cm ² . While the abrasive slurry 1 was dripped onto the surface plate at a rate of 50 mL / min, the surface plate was rotated at 40 rpm for 1 minute to polish the insulating layer.

  Thereafter, while rotating each silicon wafer, a cleaning liquid adjusted to pH 0.0 was used, supplied at 25 ° C. and a rate of 250 mL / min, and dropped for 1 minute for cleaning.

  Thereafter, pure water was dropped onto the surface of the silicon wafer at 500 ml / min for 1 minute while rotating the silicon wafer.

  Next, the silicon wafer 1 was sufficiently dried with a dryer and dried with a dryer at 120 ° C. for 10 minutes, and the polished silicon wafer 1 was taken out.

[Polishing of silicon wafers 2 to 36]
The silicon wafers 2 to 36 were polished in the same manner as the polishing of the silicon wafer 1 by changing the pH values of the abrasive particles and the abrasive slurry and the pH value of the cleaning liquid as shown in Tables 2 and 3, respectively.

<Evaluation after polishing>
1. Polishing speed Using an optical interference film thickness measuring device (manufactured by Chino Co., Ltd .: product name “IRM8599B”), the layer thickness change before and after polishing was measured, and the polishing speed (nm / min) was calculated. Further, from the results of the layer thickness measurement, it was found that the silicon oxide insulating layer produced by the TEOS-plasma CVD method had a uniform thickness over the entire wafer surface.

2. Evaluation of detergency The detergency was evaluated by counting the number of foreign matters remaining as abrasive residues on the polished wafer surface. The number of foreign matters is measured by measuring the increment of the number of DEFECTs on the wafer surface before and after polishing with a foreign matter inspection device (model surfscan SP1 manufactured by KLA-Tencor Co., Ltd.). 2 and Table 3. As the DEFECT number, a size of 0.1 to 10 μm was detected, and the unevenness of the defect was not particularly distinguished. Judgment of the result was performed by comprehensive evaluation of Table 1.

  In Tables 2 and 3, when the shape of the abrasive particles is a spherical monodisperse (the aspect ratio is within 1.10 and the variation coefficient is within 10%), it is indicated as ◯, and otherwise it is indicated as ×.

この総合評価も含めて評価結果を表２及び表３に示す。

Tables 2 and 3 show the evaluation results including this comprehensive evaluation.

  From Table 2 and Table 3, it can be seen that the number of foreign matter after polishing of the silicon wafer manufactured by the manufacturing method of the present invention is small, the polishing rate is high, and the comprehensive evaluation is excellent.

DESCRIPTION OF SYMBOLS 1 Abrasive material particle | grain 2 Polishing object film | membrane 3 Acid melt | dissolution part 4 Abrasive material particle | grains which the surface melt | dissolved and became small 5 Abrasive material particle | grains 6 and 9 Silicon substrate 7, 10 Insulating film 8 Polishing surface

Claims (5)

  A method of manufacturing a semiconductor device using an abrasive slurry containing abrasive particles containing a mixed crystal of two or more metal oxides, wherein one of the metal oxides is applied to the abrasive particles. Cerium oxide in the range of 50 to 90 mol%, and the other metal oxide is at least one selected from yttrium oxide, gadolinium oxide, lanthanum oxide, iron oxide or manganese oxide in the range of 5 to 50 mol% A polishing step in which the total of these metal oxides is 90 mol% or more, and polishing is performed using an abrasive slurry adjusted to be alkaline, and a cleaning solution adjusted to be acidic A method of manufacturing a semiconductor element, comprising:   The abrasive slurry has a pH value in terms of 25 ° C. of 8.0 to 14.0, and the cleaning solution has a pH value in terms of 25 ° C. of 0.0 to 5.0. The method of manufacturing a semiconductor device according to claim 1.   The method for manufacturing a semiconductor element according to claim 1, wherein an average particle diameter of the abrasive particles is in a range of 50 to 300 nm.   The method for manufacturing a semiconductor element according to any one of claims 1 to 3, wherein the abrasive particles are in a spherical monodisperse form.   5. The semiconductor according to claim 1, wherein a pH value in terms of 25 ° C. of the cleaning liquid adjusted to be acidic is within a range of 0.0 to 4.0. 6. Device manufacturing method.

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