Polishing composition

Abstract

[Problem] The present application has an object to provide a novel polishing composition which can reduce the residue of a polishing object such as polysilicon to be polished and also can suppress dishing. [Solution] A polishing composition which is a polishing composition containing colloidal silica, an alkali metal salt, and water, and has a pH of 9.0 to 11.5, wherein (i) the polishing composition is used in a process of polishing a second layer to expose a first layer in a polishing object having the first layer provided with a recess and the second layer formed so as to fill the recess, the first layer being selected from a layer having an oxygen-silicon bond or a layer having a nitrogen-silicon bond, the second layer having a silicon-silicon bond; and / or (ii) the colloidal silica has a silanol group number of 6 / nm 2 or more and 22 / nm 2 or more and 22 / nm

Description

TECHNICAL FIELD

[0001] The present application relates to a polishing composition. BACKGROUND

[0002] In the field of CMP, a silicon dioxide film provided with a recess and a polysilicon film formed so as to fill the recess are sometimes configured, and the silicon dioxide film is polished as a barrier layer.

[0003] As an index indicating how easily the polysilicon film is polished relative to the silicon dioxide film, the selectivity ratio of the speed at which the polysilicon film is polished to the speed at which the silicon dioxide film is polished is used. This is obtained by dividing the speed at which the polysilicon film is polished by the speed at which the silicon dioxide film is polished. In order for the silicon dioxide film to function as a barrier layer, it is preferable that the selectivity ratio be large.

[0004] Patent Document 1 aims to provide a polishing composition that can achieve a large selectivity ratio and has a small number of surface defects, and provides a polishing composition that includes a polishing material such as silicon dioxide and water, and can also include an alkaline organic compound such as tetramethylammonium hydroxide.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Publication No. 10-321569 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] The present inventors and others discovered in the course of developing a new polishing composition that in the prior art, the polysilicon buried in the recess formed of the silicon dioxide film is also excessively polished, and so-called dishing can occur. The present inventors and others discovered in the course of further research that even if the selectivity ratio is controlled, if the abrasive grains are not appropriate, or the pH of the polishing composition is not appropriate, then the polysilicon can remain after polishing, or dishing can occur.

[0010] Therefore, the present application aims to provide a new type of polishing composition that can reduce the remaining of a polishing object such as polysilicon that should be polished, and also can suppress dishing.

[0011] SOLUTION TO PROBLEM

[0012] One embodiment of the present application is a polishing composition, which is a polishing composition containing colloidal silica, an alkali metal salt, and water, having a pH of 9.0 to 11.5, wherein (i) the polishing composition is used in a process of polishing a second layer to expose a first layer in a polishing object having the first layer provided with a recess and the second layer formed so as to fill the recess, the first layer being selected from a layer having an oxygen-silicon bond or a layer having a nitrogen-silicon bond, the second layer having a silicon-silicon bond; and / or (ii) the colloidal silica has a silanol group number of 6 / nm 2 above and 22 / nm 2 below.

[0013] Effects of the Invention

[0014] According to the present application, it is possible to provide a novel polishing composition capable of reducing the residue of a polishing object to be polished such as polysilicon and also capable of suppressing dishing. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a schematic cross-sectional view of a polishing object before polishing.

[0016] Figure 2 is a schematic cross-sectional view of a polished polishing object after ideal polishing.

[0017] Figure 3 is a schematic cross-sectional view of a polished polishing object after non-ideal polishing in which dishing occurs as a defect.

[0018] Figure 4 is a schematic cross-sectional view of a polished polishing object after non-ideal polishing in which a polishing object to be polished remains as a defect.

[0019] Figure 5 is a schematic cross-sectional view of a polished polishing object in which both defects of Figure 3 and Figure 4 occur.

[0020] REFERENCE NUMERALS

[0021] 1 first layer, 2 second layer, 2a dishing, 2b residue of second layer to be polished, 10 polishing object, 10' polished polishing object. DETAILED DESCRIPTION

[0022] Hereinafter, the present application will be described in detail. Note that in this specification, "X to Y" is used in the meaning that the numerals described before and after X and Y are included as lower limit and upper limit values, and means "X or more and Y or less". In the case where a plurality of "X to Y" is described, for example, in the case where "X1 to Y1 or X2 to Y2" is described, the disclosure of each of the numerals as the upper limit, the disclosure of each of the numerals as the lower limit, and the combination of the upper limit / lower limit thereof are all disclosed (i.e., become legally valid as a modification). Specifically, the modification of X1 or more, the modification of Y2 or less, the modification of X1 or less, the modification of Y2 or more, the modification of X1 to X2, the modification of X1 to Y2, and the like must all be considered valid. Furthermore, the person skilled in the art recognizes that if the features or modes of the present disclosure are described from the viewpoint of Markush, the present disclosure is thereby described from the viewpoint of any single constituent element or a group of parts of the constituent element of Markush. In addition, unless specifically described, the operation and the measurement of physical properties and the like are measured under the conditions of room temperature (20°C to 25°C) / relative humidity 40% to 50% RH. Note that the concentration described in this specification can be the concentration at the point of use (POU) or the concentration before dilution to the concentration at the POU. The dilution ratio can be 2 times to 10 times. In addition, it should be understood that all combinations of the embodiments and explanations disclosed in this specification are disclosed in this application. That is, it must be understood that it can be legally valid as a modification. In addition, when the content or concentration of each component is described, it can be the total amount when two or more are included.

[0023] <Polishing composition>

[0024] One embodiment of the present application is a polishing composition, which is a polishing composition containing colloidal silica, an alkali metal salt, and water, and having a pH of 9.0 to 11.5, in which (i) the polishing composition is used in a process of polishing a second layer to expose a first layer in a polishing object having the first layer provided with a recess and the second layer formed so as to fill the recess, the first layer being selected from a layer having an oxygen-silicon bond or a layer having a nitrogen-silicon bond, and the second layer having a silicon-silicon bond; and / or (ii) the colloidal silica has a silanol group number of 6 to 22 per nm 2 and 22 per nm 2 Hereinafter. By this means, it is possible to provide a novel polishing composition which can reduce the residue of a polishing object such as polysilicon to be polished and also can suppress dishing. The mechanism of exhibiting such technical effects is considered as follows. In the region where the pH is basic, the hydroxide ion (OH -) becomes a silanol group (SiOH). During polishing, the polishing object that has become a silanol group (SiOH) and the colloidal silica having the number of silanol groups in the above range promote reaction by hydrogen bonding, and the residue on the pattern wafer is reduced. In addition, it is presumed that by using the alkali metal salt, excessive etching of the polishing object having a silicon-silicon bond is suppressed, and as a result, the effect of suppressing dishing is obtained. However, the mechanism is not beyond the scope of presumption, and the technical scope of the present application is not limited by the above mechanism.

[0025] In one embodiment of the present application, a process of further polishing the first layer after the first layer is exposed is included. By further including the above process, the technical effect of completely removing the residue of the polishing object such as polysilicon that should be polished is obtained.

[0026] [abrasive grains]

[0027] The polishing composition of one embodiment of the present application includes colloidal silica as an abrasive grain. The abrasive grain has a function of mechanically polishing a polishing object. The colloidal silica can be manufactured by a sol-gel method. For example, it can be obtained by performing hydrolysis and condensation reaction using a hydrolyzable silicon compound (e.g., an alkoxysilane or a derivative thereof) as a raw material.

[0028] According to one embodiment of the present application, the number of silanol groups of the colloidal silica is 6 / nm 2 or more and 22 / nm 2 or less. If the number of silanol groups of the colloidal silica is less than 6 / nm 2 or more than 22 / nm 2 , the residue of the polishing object such as polysilicon that should be polished can increase or dishing can be promoted. As a method of controlling the number of silanol groups of the colloidal silica to be 6 / nm 2 or more and 22 / nm 2 or less, for example, there is hydrothermal treatment of a dispersion liquid including the colloidal silica. As conditions of the hydrothermal treatment, the dispersion liquid including the colloidal silica is heated and treated at a temperature of, for example, 100°C to 200°C for 30 minutes to 60 minutes.

[0029] According to one embodiment of the present application, the number of silanol groups of the colloidal silica is 6.1 / nm 2 or more, 6.2 / nm 2 or more, 6.3 / nm 2 or more, 6.4 / nm 2 or more, 6.5 / nm 2 or more, 6.6 / nm 2 or more, more than 6.6 / nm 2, 6.7 per nm 2 , 6.8 per nm 2 , 6.9 per nm 2 , 7.0 per nm 2 , 7.1 per nm 2 , 7.2 per nm 2 , 7.3 per nm 2 , 7.4 per nm 2 , 7.5 per nm 2 , 7.6 per nm 2 , 7.7 per nm 2 , 7.8 per nm 2 , 9 per nm 2 , 10 per nm 2 , 12 per nm 2 , 14 per nm 2 , or 16 per nm 2 .

[0030] According to one embodiment of the present application, the colloidal silica has a silanol group number of 21 per nm 2 , 20 per nm 2 , 19 per nm 2 , 18 per nm 2 , 17.5 per nm 2 , 17 per nm 2 , 16 per nm 2 , 15 per nm 2 , 14 per nm 2 , 13 per nm 2 , 12 per nm 2 , 11 per nm 2 , 10 per nm 2 , 9 per nm 2 , 8 per nm 2 , or 7 per nm 2 . The method for measuring the silanol group number is based on the method described in the examples.

[0031] According to one embodiment of the present application, the colloidal silica has a pulse NMR specific surface area of 40 m 2 / g or less. According to one embodiment of the present application, the colloidal silica has a pulse NMR specific surface area of 39 m 2 / g or less, 38 m 2 / g or less, 37 m 2 / g or less, 36 m 2 / g or less, 35 m 2 / g or less, 34 m 2 / g or less, 33 m 2 / g or less, 32 m 2 / g or less, 31 m 2 / g or less, 30 m 2 / g or less, 29 m 2 / g or less, 28 m 2 / g or less, 27 m 2 / g or less, 26 m 2 / g or less, 25 m 2 / g or less, or 24 m 2 / g or less. According to one embodiment of the present application, the pulse NMR of the colloidal silica is 10 m 2 / g or more, 15 m 2 / g or more, or 20 m 2 / g or more. The method for measuring the pulse NMR specific surface area of the abrasive particles (particularly, the colloidal silica) is based on the method described in the examples. The pulse NMR specific surface area of the colloidal silica can be controlled by increasing or decreasing the number of protons of the functional groups on the surface of the colloidal silica in such a manner that the relaxation speed of the proton resonance varies depending on the amount of molecules adsorbed on the surface of the solid.

[0032] According to one embodiment of the present application, the lower limit of the average primary particle diameter of the abrasive particles (particularly, the colloidal silica) is 60 nm or more, 70 nm or more, more than 70 nm, 71 nm or more, 72 nm or more, 73 nm or more, 74 nm or more, 75 nm or more, 76 nm or more, 77 nm or more, 78 nm or more, 79 nm or more, 80 nm or more, 81 nm or more, 82 nm or more, 83 nm or more, 84 nm or more, 85 nm or more, 86 nm or more, 87 nm or more, 88 nm or more, 89 nm or more, or 95 nm or more.

[0033] According to one embodiment of the present application, the upper limit of the average primary particle diameter of the abrasive particles (particularly, the colloidal silica) is 110 nm or less, less than 100 nm, 99 nm or less, 98 nm or less, 97 nm or less, 96 nm or less, 95 nm or less, 94 nm or less, 93 nm or less, 92 nm or less, or 91 nm or less. According to one embodiment of the present application, the average primary particle diameter of the aforementioned colloidal silica is greater than 70 nm and less than 100 nm. The method for measuring the average primary particle diameter is based on the method described in the examples.

[0034] According to one embodiment of the present application, the lower limit of the average secondary particle diameter of the abrasive grains (particularly, colloidal silica) is 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, 160 nm or more, 170 nm or more, 180 nm or more, 190 nm or more, 200 nm or more, 210 nm or more, or 215 nm or more.

[0035] According to one embodiment of the present application, the upper limit of the average secondary particle diameter of the abrasive grains (particularly, colloidal silica) is 350 nm or less, 340 nm or less, 330 nm or less, 320 nm or less, 310 nm or less, 300 nm or less, 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less, 250 nm or less, 240 nm or less, 230 nm or less, or 225 nm or less. The method for measuring the average secondary particle diameter is based on the method described in the Examples.

[0036] According to one embodiment of the present application, the average association degree (average secondary particle diameter / average primary particle diameter) of the abrasive grains (particularly, colloidal silica) is 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, 2.1 or more, 2.2 or more, 2.3 or more, or 2.4 or more.

[0037] According to one embodiment of the present application, the average association degree (average secondary particle diameter / average primary particle diameter) of the abrasive grains (particularly, colloidal silica) is 4.6 or less, 4.4 or less, 4.2 or less, 4.0 or less, 3.8 or less, 3.6 or less, 3.4 or less, 3.2 or less, 3.0 or less, 2.9 or less, 2.8 or less, 2.7 or less, 2.6 or less, or 2.5 or less.

[0038] According to one embodiment of the present application, the content ratio of the abrasive grains (particularly, colloidal silica) in the polishing composition is 0.01 mass% or more, 0.05 mass% or more, 0.1 mass% or more, 0.5 mass% or more, 0.6 mass% or more, 0.7 mass% or more, 0.8 mass% or more, 0.9 mass% or more, 1.0 mass% or more, 1.1 mass% or more, 1.2 mass% or more, 1.3 mass% or more, or 1.4 mass% or more.

[0039] According to one embodiment of the present application, the content ratio of the abrasive grains (particularly, colloidal silica) in the polishing composition is 10 mass% or less, 5 mass% or less, 3 mass% or less, or 2 mass% or less.

[0040] According to one embodiment of the present application, the abrasive grains contained in the polishing composition are 90 mass% or more, 95 mass% or more, 98 mass% or more, 99 mass% or more, 99.5 mass% or more, or 99.9 mass% or more (upper limit: 100 mass%) of colloidal silica.

[0041] According to one embodiment of the present application, the surface of the abrasive grains (particularly, colloidal silica) contained in the polishing composition is not subjected to a treatment such that a chemical bond of a treating agent such as an organic acid (e.g., sulfonic acid, carboxylic acid) is formed.

[0042] [Alkali metal salt]

[0043] The polishing composition of one embodiment of the present application contains an alkali metal salt. If the polishing composition does not contain an alkali metal salt, it can be difficult to reduce the residue of the polishing object such as polysilicon to be polished or to promote the recess.

[0044] According to one embodiment of the present application, as the alkali metal salt, at least one of a hydroxide of an alkali metal and a carbonate of an alkali metal is contained. According to one embodiment of the present application, the alkali metal salt includes a hydroxide of an alkali metal. As the alkali metal salt, from the viewpoint of reducing the recess and reducing the residual metal, a hydroxide of an alkali metal is preferable to a carbonate of an alkali metal. According to one embodiment of the present application, potassium hydroxide is contained as the hydroxide of an alkali metal. As the alkali metal, potassium, sodium, lithium, and the like can be given, and from the viewpoint of reducing the residual metal, potassium is particularly preferable.

[0045] The alkali metal salt also functions as a pH adjuster for adjusting the pH of the polishing composition. According to one embodiment of the present application, the content of the pH adjuster (particularly, the alkali metal salt) contained in the polishing composition is an amount appropriate for adjusting the polishing composition to a predetermined pH (particularly, pH 9.0 to 11.5).

[0046] According to one embodiment of the present application, the alkali metal salt (particularly, potassium hydroxide) in the pH adjuster contained in the polishing composition is 90 mass% or more, 95 mass% or more, 98 mass% or more, 99 mass% or more, 99.5 mass% or more, or 99.9 mass% or more (upper limit: 100 mass%). According to one embodiment of the present application, the potassium hydroxide in the pH adjuster contained in the polishing composition is 90 mass% or more, 95 mass% or more, 98 mass% or more, 99 mass% or more, 99.5 mass% or more, or 99.9 mass% or more (upper limit: 100 mass%). Note that even if the abrasive grains (particularly, colloidal silica) and the preservative which can be arbitrarily contained have a function of slightly changing the pH of the polishing composition, the ability to change the pH is low, and thus in the present application, they are not included in the category of the pH adjuster.

[0047] [pH]

[0048] The pH of the polishing composition of one embodiment of the present application is 9.0 to 11.5. When the pH of the polishing composition is less than 9.0 or more than 11.5, it can be impossible to reduce the residue of the polishing object such as polysilicon to be polished or the recess is promoted.

[0049] According to one embodiment of the present application, the pH of the polishing composition is 9.1 or more, 9.2 or more, 9.3 or more, 9.4 or more, 9.5 or more, more than 9.5, 9.6 or more, 9.7 or more, 9.8 or more, 9.9 or more, or 10.5 or more. According to one embodiment of the present application, the pH of the polishing composition is 11.5 or less, 11.4 or less, 11.3 or less, 11.2 or less, 11.1 or less, 11 or less, less than 11, 10.9 or less, 10.8 or less, 10.7 or less, 10.6 or less, 10.5 or less, 10.4 or less, 10.3 or less, 10.2 or less, 10.1 or less, or 9.8 or less.

[0050] According to one embodiment of the present application, the pH of the polishing composition is not 9.1, 9.2, 9.3, 9.4, 9.6, 9.7, 9.8, 9.9, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.1, 11.2, 11.3, 11.4, or 11.5. The method for measuring the pH of the polishing composition is based on the method described in the examples.

[0051] [Polishing object]

[0052] According to one embodiment of the present application, the polishing composition is used in a process of polishing the second layer to expose the first layer in a polishing object having a first layer provided with a recess and a second layer formed so as to fill the recess. Figure 1 is a schematic cross-sectional view of a (pre-polishing) polishing object. As shown in the upper drawing of Figure 1 is provided with a first layer 1 (a film having an oxygen-silicon bond or a film having a nitrogen-silicon bond) formed so as to provide a recess. Then, as shown in the lower drawing of Figure 1 is provided with a second layer 2 (a film having a silicon-silicon bond) formed so as to fill the recess, whereby a polishing object 10 including the first layer and the second layer is formed.

[0053] If the polishing composition of the present application is applied to such a polishing object 10, as shown in Figure 2As shown, the polished object 10' after polishing, which is a polished object after polishing, has a desired polished surface in which the remaining of the polishing object (film having a silicon-silicon bond) to be polished is reduced (no remaining) and the recess is also suppressed (not generated). In addition, by applying the polishing composition of the present application, the number of metal atoms that can remain after polishing can also be reduced. According to one embodiment of the present application, the number of metal atoms remaining per 1 cm 2 in the polished object after polishing (unit: x 10 10 atoms / cm 2 ) is 40 or less, less than 38, less than 35, 30 or less, 25 or less, 20 or less, or less than 19. According to one embodiment of the present application, the number of metal atoms remaining per 1 cm 2 in the polished object after polishing (unit: x 10 10 atoms / cm 2 ) is, for example, 0, 0.01 or more, 0.5 or more, 1 or more, 5 or more, or 10 or more. If the polishing object 10 including the first layer and the second layer is polished with a polishing composition other than the polishing composition of the present application (i.e., a comparative example polishing composition), a recess 2a is generated as shown in, for example, Figure 3 , or a remaining 2b of the polishing object (film having a silicon-silicon bond) to be polished is generated as shown in, for example, Figure 4 , or both of them are generated as shown in, for example, Figure 5 .

[0054] In one embodiment of the present application, as the polishing object having an oxygen-silicon bond, TEOS-type silicon oxide (hereinafter, also simply referred to as "TEOS") generated using tetraethyl orthosilicate as a precursor, HDP (high density plasma), USG (undoped silicate glass), PSG (phosphosilicate glass), BPSG (borophosphosilicate glass), or RTO (rapid thermal oxidation), and the like can be listed. The TEOS film can be formed by plasma CVD.

[0055] In one embodiment of the present application, as the polishing object having a nitrogen-silicon bond, a silicon nitride film or SiCN (silicon carbon nitride), and the like can be listed. Among them, the first layer is preferably a silicon oxide film (TEOS film) derived from tetraethyl orthosilicate. In one embodiment of the present application, as the polishing object having a silicon-silicon bond, polysilicon, amorphous silicon, single crystal silicon, n-type doped single crystal silicon, p-type doped single crystal silicon, SiGe, and the like Si-based alloys, and the like can be listed. Among them, the second layer is preferably polycrystalline silicon such as polysilicon.

[0056] [Polishing Rate]

[0057] According to one embodiment of the present application, the polishing composition has a polishing rate of the second layer of or more, or more, or more, or more, or more, or more. According to one embodiment of the present application, the polishing composition has a polishing rate of the second layer of or less, or less.

[0058] According to one embodiment of the present application, the polishing composition has a polishing rate of the first layer of or more, or more, or more, or more. According to one embodiment of the present application, the polishing composition has a polishing rate of the first layer of or less, or less, or less, or less, or less, or less.

[0059] [Selection ratio]

[0060] According to one embodiment of the present application, the polishing composition has a property that the polishing rate of the aforementioned second layer with respect to the polishing rate of the aforementioned first layer (selection ratio) is 17 to 40, or 20 to 40. If the selection ratio is less than 17 or exceeds 40, it can be impossible to reduce the residue of the polishing target such as polysilicon, which should be polished, or the concave is promoted.

[0061] According to one embodiment of the present application, the polishing composition has a property that the selection ratio is 17 or more, 18 or more, 19 or more, 20 or more, 21 or more, 22 or more, 23 or more, 24 or more, 25 or more, 26 or more, 27 or more, 28 or more, 29 or more, 30 or more, 31 or more, 32 or more, 33 or more, 34 or more, or 35 or more.

[0062] According to one embodiment of the present application, the polishing composition has a property that the selection ratio is 39 or less, 37 or less, 35 or less, 33 or less, 31 or less, or 29 or less.

[0063] [Transmittance]

[0064] According to one embodiment of the present application, the transmittance of the polishing composition when light of a wavelength of 450 nm is transmitted is greater than 0.1% and less than 1% when the concentration of the abrasive grains (particularly, colloidal silica) contained in the polishing composition is 1.5% by mass. According to this embodiment, by increasing the mechanical action on the polishing object to be polished such as polysilicon, there is an effect of reducing the residue on the pattern wafer. As a method of adjusting the transmittance to the above range, for example, a method of adjusting the particle diameter of the colloidal silica and a method of adjusting the electric conductivity can be cited.

[0065] According to one embodiment of the present application, the transmittance is 0.13% or more or 0.5% or more. According to one embodiment of the present application, the transmittance is 0.9% or less, 0.7% or less, 0.5% or less, or 0.3% or less.

[0066] Here, when the abrasive grain concentration of the polishing composition is not 1.5% by mass, adjustment of the abrasive grain concentration to 1.5% by mass can be performed as follows. That is, when the abrasive grain concentration of the polishing composition exceeds 1.5% by mass, an appropriate amount of water can be added so that the abrasive grain concentration becomes 1.5% by mass. When the abrasive grain concentration of the polishing composition is less than 1.5% by mass, the polishing composition can be stored in an environment of 25°C to 40°C until the abrasive grain concentration reaches 1.5% by mass, or a treatment such as ultrafiltration can be performed.

[0067] [Water]

[0068] The polishing composition of one embodiment of the present application contains water as an aqueous carrier. According to one embodiment of the present application, the aqueous carrier is not limited to containing an alcohol such as methanol, ethanol, ethylene glycol, or a ketone such as acetone, and the water in the aqueous carrier is 90% by mass or more, 95% by mass or more, 98% by mass or more, 99% by mass or more, 99.5% by mass or more, or 99.9% by mass or more (the upper limit is 100% by mass).

[0069] [Preservative]

[0070] According to one embodiment of the present application, the polishing composition contains a preservative. As the preservative, for example, an isothiazolin-based preservative such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, a p-hydroxybenzoic acid ester-based preservative such as methyl p-hydroxybenzoate (methyl paraben) and ethyl p-hydroxybenzoate (ethyl paraben), and phenoxyethanol can be cited. These preservatives can be used alone or in combination with two or more.

[0071] According to one embodiment of the present application, the polishing composition can contain a preservative at 0.001 to 1% by mass, 0.005 to 0.5% by mass, or 0.01 to 0.1% by mass.

[0072] According to one embodiment of the present application, there is provided an abrasive composition which substantially contains only colloidal silica, an alkali metal salt, a preservative, and water, the pH of the abrasive composition being 9.0 to 11.5. 2 The above and 22 / nm 2 The following colloidal silica, alkali metal salt, preservative, and water constitute the abrasive composition, the pH of which is 9.0 to 11.5.

[0073] [Other components]

[0074] The abrasive composition of the present application is preferably simply constituted, i.e., preferably contains as few components as possible other than colloidal silica, an alkali metal salt (particularly potassium hydroxide), and water and an optional preservative. In the case of containing components other than colloidal silica, an alkali metal salt (particularly potassium hydroxide), and water and an optional preservative, the ratio of the components (the total of them) is preferably 0.1% by mass or less, 0.01% by mass or less, 0.001% by mass or less, or less than 0.0001% by mass in the abrasive composition. The concentration of a certain one or more components (2 or more when it is 2 or more) other than colloidal silica, an alkali metal salt (particularly potassium hydroxide), and water and an optional preservative in the abrasive composition is 0.1% by mass or less, 0.01% by mass or less, 0.001% by mass or less, or less than 0.0001% by mass is also referred to as "substantially not containing" the component (the components).

[0075] According to one embodiment of the present application, the abrasive composition substantially does not contain at least any one of hydroxyethyl cellulose (HEC), polyacrylic acid (PAA), polyoxyethylene (POE) lauryl ether, dodecylbenzenesulfonic acid (DBS), hydrogen peroxide (H2O2), ammonia (ammonium ion), and amine. "At least any one" is explained by citing several cases, for example, including the case where the abrasive composition substantially does not contain hydroxyethyl cellulose (HEC) (i.e., the abrasive composition does not contain hydroxyethyl cellulose (HEC) at all (below the detection limit), or even if it contains, it is 0.1% by mass or less, 0.01% by mass or less, 0.001% by mass or less, or less than 0.0001% by mass), the case where the abrasive composition substantially does not contain hydroxyethyl cellulose (HEC) and polyacrylic acid (PAA) (i.e., the abrasive composition does not contain either of hydroxyethyl cellulose (HEC) and polyacrylic acid (PAA) at all (below the detection limit), or even if it contains, it is 0.1% by mass or less, 0.01% by mass or less, 0.001% by mass or less, or less than 0.0001% by mass) and the like. The concept of "substantially does not contain at least any one" in the present specification should be understood as such by those skilled in the art.

[0076] According to one embodiment of the present application, the polishing composition substantially does not contain a polyoxyalkylene alkyl ether. According to one embodiment of the present application, the polishing composition substantially does not contain an alkyl aryl sulfonic acid.

[0077] According to one embodiment of the present application, the polishing composition substantially does not contain at least any one of a water-soluble polymer, a surfactant, an oxidizing agent, and a compound having a nitrogen atom. According to one embodiment of the present application, the content of the surfactant in the polishing composition is less than 0.001 mass%, 0.0005 mass% or less, 0.0001 mass% or less, or a detection limit or less.

[0078] According to one embodiment of the present application, the water-soluble polymer refers to a substance of which the mass of insoluble matter filtered out when a 0.5 mass% concentration of the water-soluble polymer is dissolved in water at the temperature at which the water-soluble polymer is most soluble and filtered with a G2 glass filter (maximum pore size 40 μm to 50 μm) is within 50 mass% of the water-soluble polymer added. According to one embodiment of the present application, "water-soluble" refers to a solubility in water (25°C) of 1 g / 100 mL or more, and "high polymer" refers to a (co)polymer having a repeating unit in its molecular structure and a weight average molecular weight (Mw) of 1,000 or more. According to one embodiment of the present application, as the water-soluble polymer, for example, nonionic water-soluble polymers such as polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), pullulan, hydroxyethyl cellulose, and the like; anionic water-soluble polymers such as polyacrylic acid, carboxymethyl cellulose, and the like; and cationic water-soluble polymers such as polyacrylamide, and the like can be listed. According to one embodiment of the present application, the polishing composition substantially does not contain at least one of them. "At least one of them" is explained by listing a few cases, for example, a case where the polishing composition substantially does not contain a nonionic water-soluble polymer (i.e., the polishing composition does not contain a nonionic water-soluble polymer at all (below the detection limit), or even if it contains, it is 0.1 mass% or less, 0.01 mass% or less, 0.001 mass% or less, or less than 0.0001 mass%), a case where the polishing composition substantially does not contain a nonionic water-soluble polymer and a cationic water-soluble polymer (i.e., the polishing composition does not contain either of a nonionic water-soluble polymer and a cationic water-soluble polymer at all (below the detection limit), or even if it contains, it is 0.1 mass% or less, 0.01 mass% or less, 0.001 mass% or less, or less than 0.0001 mass% in total), a case where the polishing composition substantially does not contain polyvinyl alcohol (PVA), polyacrylic acid, and polyacrylamide (i.e., the polishing composition does not contain any of polyvinyl alcohol (PVA), polyacrylic acid, and polyacrylamide at all (below the detection limit), or even if it contains, it is 0.1 mass% or less, 0.01 mass% or less, 0.001 mass% or less, or less than 0.0001 mass% in total), and the like. The concept of "substantially does not contain at least one of them" in this specification should be understood as such by those skilled in the art.

[0079] Surfactants are substances that possess both hydrophilic and hydrophobic groups. Examples of surfactants include alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene oleyl ether; alkyl phenyl ethers such as polyoxyethylene octylphenyl ether; alkyl esters such as polyoxyethylene lauryl ester; alkylamines such as polyoxyethylene lauryl amino ether; alkylamides such as polyoxyethylene lauramide; polypropylene glycol ethers such as polyoxyethylene polyoxypropylene ether; alkanolamides such as oleic acid diethanolamide; and allyl phenyl ethers such as polyoxyalkylene allylphenyl ether.

[0080] In addition, examples include nonionic surfactants such as propylene glycol, diethylene glycol, monoethanolamine, alcohol ethoxylates, alkylphenol ethoxylates, tert-acetylenol, and alkanolamides; carboxylic acid surfactants such as sodium myristate, sodium palmitate, sodium stearate, sodium laurylate, and potassium laurylate; sulfate surfactants such as sodium octyl sulfate; phosphate surfactants such as lauryl phosphate and sodium lauryl phosphate; anionic surfactants such as sodium dioctyl sulfosuccinate and sodium dodecylbenzene sulfonate; cationic surfactants such as dodecylamine hydrochloride and amines; or amphoteric surfactants such as alkyl betaines and sulfobetaines, including lecithin, alkylamine oxides, and N-alkyl-N,N-dimethylammonium betaine. According to one embodiment of the present invention, the grinding composition substantially does not contain at least one of these surfactants.

[0081] The oxidant can be a substance having a higher redox potential than that of the substrate material (especially polycrystalline silicon) at the pH where the grinding is performed. Here, the pH at which the grinding is performed is usually the same as the pH of the grinding composition. It should be noted that the redox potential of the substrate material can be obtained by dispersing powder of the material (especially polycrystalline silicon) in water to form a slurry, adjusting the slurry to the same pH as the grinding composition, and then measuring the redox potential of the slurry (redox potential against a standard hydrogen electrode at a liquid temperature of 25°C) using a commercially available redox potentiometer. Examples of such oxidants include hydrogen peroxide, metal oxides, peroxides, nitrates, iodates, periodate, hypochlorite, chlorite, chlorate, perchlorate, persulfate, dichromate, permanganate, organic oxidants, ozone water, and silver (II) salts, iron (III) salts, etc. According to one embodiment of the invention, the grinding composition substantially does not contain at least one of these.

[0082] As a compound having a nitrogen atom, for example, there can be mentioned hydroxides, chlorides, carbonates, sulfates, phosphates, and the like of tetramethylammonium, tetraethylammonium, tetrabutylammonium, and the like. As specific examples, there can be mentioned tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and the like, tetraalkylammonium salts such as tetramethylammonium carbonate, tetramethylammonium chloride, and the like, and quaternary ammonium compounds such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, anhydrous piperazine, piperazine hexahydrate, l-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine, and the like, or ammonia. According to one embodiment of the present application, the polishing composition substantially does not contain at least one of them. According to one embodiment of the present application, the content (mass %) of a compound having a nitrogen atom represented by the formula: N(R 1 )(R 2 )(R 3 )(R 4 ) (wherein R 1 to R 4 each independently represent an alkyl group, which is optionally substituted with an alkyl group, an aryl group, or a hydroxyl group) in the polishing composition is less than 0.005 mass %, 0.001 mass % or less, 0.0005 mass % or less, 0.0001 mass % or less, or the detection limit or less.

[0083] According to one embodiment of the present application, the polishing composition does not contain a high molecular compound containing a lactam ring, or even if it contains, it is less than 0.0001 mass %.

[0084] According to one embodiment of the present application, the polishing composition substantially does not contain a polishing grain other than colloidal silica.

[0085] According to one embodiment of the present application, the polishing composition substantially does not contain silica having an acidic group (for example, a sulfo group, a carboxyl group, a phosphoric acid group, and the like) derived from an organic acid fixed on the surface.

[0086] According to one embodiment of the present application, the polishing composition substantially does not contain silica having an amino group fixed on the surface.

[0087] According to one embodiment of the present application, the polishing composition substantially does not contain an organic acid.

[0088] According to one embodiment of the present application, the polishing composition substantially does not contain a phosphoric acid ester. In the present specification, "substantially does not contain a phosphoric acid ester" means that the polishing composition can contain less than 0.001 mass % in addition to not containing a phosphoric acid ester at all (the detection limit or less).

[0089] In one embodiment of the present invention, a grinding composition is provided, which is substantially composed only of silanol groups with a number of 6 per nm. 2 Above and 22 per nm 2 The following composition comprises colloidal silica, alkali metal salt, and water, and the pH of the grinding composition is 9.0 to 11.5. The above description applies to the description of colloidal silica, alkali metal salt (especially potassium hydroxide), water, pH, and preservatives. "Substantially...composes" means that when the grinding composition contains components other than colloidal silica, alkali metal salt (especially potassium hydroxide), water, and optionally a preservative, the proportion of these components (in total) in the grinding composition is less than 0.1% by mass, less than 0.01% by mass, less than 0.001% by mass, or less than 0.0001% by mass.

[0090] According to one embodiment of the present invention, the grinding composition substantially does not contain at least one of the following substances: R 1 R 2 R 3 R 4 N + X - R 1 R 2 R 3 R 4 P + X - R 1 R 2 R 3 S + X - Imidazolium salts and pyridinium salts, wherein R 1 R 2 R 3 and R 4 Each is independently a C1-C6 alkyl group, C7-C6 alkyl group, or C6-C6 alkyl group. 12 Arylalkyl or C6-C 10 Aryl, X - It is an anion.

[0091] According to one embodiment of the invention, the grinding composition substantially does not contain at least one of hydroxyalkyl cellulose, carrageenan, and xanthan gum.

[0092] In one embodiment of the present application, the polishing composition can be of a single component type, or of a multi-component type typified by a two-component type. In addition, the polishing composition of one embodiment of the present application can be used as a polishing liquid after being diluted, typically with water, or can be used directly as a polishing liquid. That is, the concept of the polishing composition in the technology to which the present application pertains includes both a polishing composition (working slurry) supplied to a polishing target for polishing of the polishing target and a concentrated liquid (stock solution of the working slurry) diluted for polishing. The concentration ratio of the above-mentioned concentrated liquid can be set to about 2 to 100 times, for example, on a volume basis.

[0093] <Method for producing polishing composition>

[0094] In one embodiment of the present application, the method for producing a polishing composition has a step of adjusting the pH to 9.0 to 11.5 by including colloidal silica, an alkali metal salt (particularly, potassium hydroxide), water, and optionally a preservative, other components, and the like. The descriptions of the colloidal silica, the alkali metal salt (particularly, potassium hydroxide), the water, the pH, the preservative, and the other components can be applied to the above-described descriptions. The temperature at the time of mixing the components is not particularly limited, and is preferably 10°C or higher and 40°C or lower, and heating can be performed in order to improve the dissolution rate. In addition, the mixing time is not particularly limited as long as uniform mixing is possible.

[0095] <Method for polishing polishing target>

[0096] In one embodiment of the present application, as shown in Figure 1 the method for polishing a polishing target has a step of polishing the second layer 2 to expose the first layer 1 in a polishing target 10 having a first layer 1 (a layer having an oxygen-silicon bond or a layer having a nitrogen-silicon bond) provided with a recess and a second layer 2 (a layer having a silicon-silicon bond) formed so as to fill the recess. In one embodiment of the present application, the step of further polishing the first layer after the first layer is exposed is included. By further including the above-described step, the technical effect of completely removing the residue of the polishing target such as polysilicon which should be polished is obtained.

[0097] In one embodiment of the present application, as shown in Figure 1 a first layer 1 (a layer having an oxygen-silicon bond or a layer having a nitrogen-silicon bond) is formed on an arbitrary film (for example, a Si substrate) so as to be provided with a recess. Then, a second layer 2 (a film having a silicon-silicon bond) is formed so as to fill the recess, and the second layer 2 is laminated in excess so as to be exposed from the recess of the first layer 1, thereby forming a polishing target 10 including the first layer 1 and the second layer 2. Such a polishing target 10 is polished by a polishing device capable of supplying the polishing composition of the present application.

[0098] In one embodiment of the present invention, a general grinding apparatus can be used as a grinding device, which is equipped with a support for holding a substrate or the like with the object to be ground and a motor or the like with a speed that can be changed, and has a grinding platform on which a grinding pad (grinding cloth) can be attached.

[0099] In one embodiment of the invention, the abrasive pad can be made of general nonwoven fabric, polyurethane, or porous fluoropolymer, without particular limitation. Preferably, the abrasive pad is subjected to a troughing process to collect the abrasive fluid.

[0100] In one embodiment of the present invention, the grinding conditions, such as the rotational speed of the grinding platform and the carrier, are preferably independently between 10 rpm and 500 rpm. The pressure applied to the substrate having the object to be ground (grinding pressure) is preferably between 0.5 and 10 psi. There are no particular limitations on the method of supplying the grinding composition to the grinding pad; for example, a continuous supply method using a pump or the like can be employed. The supply amount is not limited, but it is preferable that the surface of the grinding pad is always covered by the grinding composition of the present invention.

[0101] like Figure 2 As shown, by applying the grinding composition of the present invention, the ground grinding object 10', which is the ground grinding object after grinding, has an ideal grinding surface with reduced (no residue) of the grinding object to be ground and suppressed (no depressions).

[0102] The present invention includes the following methods and forms.

[0103] 1. A polishing composition comprising colloidal silica, an alkali metal salt, and water, having a pH of 9.0 to 11.5, wherein (i) the polishing composition is used in a process of polishing a workpiece having a first layer having recesses and a second layer formed in such a way as to fill the recesses, thereby exposing the first layer, wherein the first layer is selected from a layer having oxygen-silicon bonds or a layer having nitrogen-silicon bonds, and the second layer has silicon-silicon bonds; and / or (ii) the colloidal silica has 6 silanol groups per nm. 2 Above and 22 per nm 2 the following.

[0104] 2. The grinding composition according to 1, wherein the grinding speed of the second layer is 17 to 40 relative to the grinding speed of the first layer.

[0105] 3. The grinding composition according to 1 or 2, wherein the specific surface area of ​​the colloidal silica by pulse NMR is 40 m². 2 / g or less.

[0106] 4. The grinding composition according to any one of claims 1 to 3, wherein the average primary particle size of the colloidal silica is greater than 70 nm and less than 100 nm.

[0107] 5. The grinding composition according to any one of 1. to 4, wherein the alkali metal salt is an alkali metal hydroxide.

[0108] 6. The grinding composition according to 5, wherein the hydroxide of the alkali metal is potassium hydroxide.

[0109] 7. The grinding composition according to any one of 1. to 6, substantially free from at least one of HEC, PAA, POE lauryl ether, DBS, H2O2, ammonia and amine.

[0110] 8. The grinding composition according to any one of 1 to 7, wherein it substantially does not contain at least any one of a water-soluble polymer, a surfactant, an oxidant, and a compound having a nitrogen atom.

[0111] 9. The polishing composition according to any one of 1. to 7, wherein, when the concentration of the colloidal silica is 1.5% by mass, the transmittance when light with a wavelength of 450 nm is transmitted is greater than 0.1% and less than 1%.

[0112] 10. A grinding composition, substantially consisting only of 6 silanol groups per nm. 2 Above and 22 per nm 2 The composition comprises colloidal silica, alkali metal salt and water, and the pH of the grinding composition is 9.0 to 11.5.

[0113] 11. A grinding composition, substantially consisting only of 6 silanol groups per nm. 2 Above and 22 per nm 2 The composition comprises colloidal silica, alkali metal salt, preservative and water, and the pH of the grinding composition is 9.0 to 11.5.

[0114] Example

[0115] The present invention is further described in detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. In addition, unless otherwise specified, the operation is carried out at room temperature (25°C) and relative humidity of 40-50% RH.

[0116] <Preparation of Grinding Compositions>

[0117] A polishing composition was prepared by mixing abrasive grains, an alkali metal salt, and water in such a manner as to have the composition shown in Table 1. For example, the polishing composition of Example 1 was a composition containing colloidal silica having a pulse NMR specific surface area of 23.8 m 2 / g, a silanol group number of 7.9 groups / nm 2 , and an average primary particle diameter of 90 nm and an average secondary particle diameter of 220 nm, potassium hydroxide, and water, and having a pH of 10.

[0118] <Method for calculating particle diameter>

[0119] The average primary particle diameter of the abrasive grains was calculated from the specific surface area of the abrasive grains based on the BET method and the density of the abrasive grains, measured using "Macsorb HM model-1210" manufactured by Mountech Co., Ltd.

[0120] The average secondary particle diameter of the abrasive grains was measured using a dynamic light scattering particle size / particle size distribution device UPA-UT 151 manufactured by Nikkiso Co., Ltd.

[0121] <Method for calculating silanol group number>

[0122] The silanol group number per unit surface area of the abrasive grains (units: groups / nm 2 ) was calculated after each parameter was measured or calculated by the following measurement method or calculation method.

[0123] More specifically, C in the following formula is the total mass of the abrasive grains, and S in the following formula is the BET specific surface area of the abrasive grains. More specifically, first, 1.50 g of the abrasive grains as a solid component was collected in a 200-ml beaker, and 100 ml of pure water was added to make a slurry, and then 30 g of sodium chloride was added to dissolve. Next, the pH of the slurry was adjusted to 3.0 to 3.5 by adding 1N hydrochloric acid, and then pure water was added until the slurry reached 150 ml.

[0124] For this slurry, using an automatic titration device (COM-1700 manufactured by Hirano Seiki Co., Ltd.), the pH was adjusted to 4.0 at 25°C using 0.1N sodium hydroxide, and further, the volume V [L] of the 0.1N sodium hydroxide solution required to increase the pH from 4.0 to 9.0 was measured by pH titration. The average silanol group density (silanol group number) can be calculated by the following formula.

[0125] ρ = (C x V x N A ) / (C x S)

[0126] In the above formula, p represents the average silanol group density (silanol group number) (groups / nm 2); c represents the concentration (mol / L) of the sodium hydroxide solution used in the titration; V represents the volume (L) of the sodium hydroxide solution required to raise the pH from 4.0 to 9.0; N A represents the Avogadro constant (1 / mol); C represents the total mass (solid content) of the abrasive grains (g); S represents the weighted average value of the BET specific surface area of the abrasive grains (nm 2 The BET specific surface area is a value of the specific surface area of the abrasive grains based on the BET method, which is measured using "Macsorb HM model-1210" manufactured by Mountech Corporation.

[0127] <Method for measuring the specific surface area by pulse NMR>

[0128] Each of the abrasive grains (raw material colloidal silica) was dispersed in water so as to become a dispersion liquid at a concentration of 20 mass%, and the dispersion liquid was prepared as a sample. The specific surface area was measured using a pulse NMR particle interface property evaluation device (manufactured by Xigo nanotools Corporation) under the following measurement conditions, and the results are shown in Table 1.

[0129] Measurement conditions

[0130] Volume relaxation time: 2409 ms

[0131] Specific surface area relaxation rate: 0.00026

[0132] Volume ratio of particles to liquid: 0.1136.

[0133] <Measurement of the pH of the polishing composition>

[0134] After 3-point calibration using standard buffers (phthalate pH buffer pH: 4.01 (25°C), neutral phosphate pH buffer pH: 6.86 (25°C), carbonate pH buffer pH: 10.01 (25°C)) using a glass electrode type hydrogen ion concentration indicator (manufactured by HORIBA, Ltd., Model No. F-23), the glass electrode was placed in the polishing composition, and the value after stabilization for 2 minutes or more was measured as the pH of the polishing composition.

[0135] <Measurement of the transmittance of the polishing composition>

[0136] The transmittance of the polishing composition was measured by irradiating the polishing composition with light having a wavelength of 450 nm using an ultraviolet-visible spectrophotometer (UV-2450, manufactured by Shimadzu Corporation). The results are shown in Table 1.

[0137] <Measurement of the polishing rate>

[0138] The surface of the object to be polished was polished using the polishing composition under the following polishing conditions. In addition, as the object to be polished, a silicon wafer (300 mm, blank wafer) having a poly-silicon (Poly-Si) film with a thickness of 1000 nm formed on the surface and a silicon wafer (300 mm, blank wafer) having a P-TEOS film (TEOS film (silicon dioxide film) formed by plasma CVD) with a thickness of 1000 nm formed on the surface were used, respectively.

[0139] (Polishing conditions)

[0140] Polishing device: 300 mm CMP single-side polishing device FREX 300E manufactured by Nippon Gohsei Co., Ltd.

[0141] Pad: Hard polyurethane pad IC 1010 manufactured by Nitta Haas Co., Ltd.

[0142] Polishing pressure: 2.2 psi (1 psi = 6894.76 Pa, same below)

[0143] Polishing table rotation speed: 70 rpm

[0144] Carrier rotation speed: 70 rpm

[0145] Supply of polishing composition: Pouring

[0146] Amount of supply of polishing composition: 200 ml / min

[0147] Polishing time: 60 seconds.

[0148] The polishing rate was determined by calculating (thickness before polishing) - (thickness after polishing) divided by the polishing time. In addition, the ratio of the polishing rate of the poly-silicon film (nm / min) to the polishing rate of the P-TEOS film (nm / min) was calculated as the selectivity ratio. The results are shown in Table 1. <Recess evaluation of poly-silicon>

[0149] The polishing of the pattern wafer with a poly-silicon film was performed by [Condition 1] described below using the polishing composition. As shown in Table 2, the pattern wafer was a wafer in which a P-TEOS film

[0150] was laminated on a Si substrate, and a recess was formed by digging a groove with a depth of 1000 nm, and then laminated in a manner to fill the recess with a poly-silicon film Figure 1

[0151] ​​​​​​​The polishing of the pattern wafer with the polysilicon film described above is further continued for a time corresponding to 40% of the polishing time until the end point signal is detected after the end point signal is detected. In this way, a process of further polishing the first layer (P-TEOS film) after the first layer (P-TEOS film) is exposed is realized.

[0152] In the 1 μm wide isolated wiring portion on the surface of the pattern wafer, the amount of recess was measured using an atomic force microscope (trade name: WA-1300, manufactured by Hitachi Kenki Fine Tech Co., Ltd.). The amount of recess thus obtained was evaluated according to the following evaluation criteria.

[0153] [Condition 1]

[0154] Polishing device: 300 mm CMP single-side polishing device FREX 300E manufactured by Kabushiki Kaisha Nessho Seizo

[0155] Pad: hard polyurethane pad IC 1010 manufactured by Nitta Haas Kabushiki Kaisha

[0156] Polishing pressure: 2.2 psi (1 psi = 6894.76 Pa, same below)

[0157] Polishing table rotation speed: 70 rpm

[0158] Carrier rotation speed: 70 rpm

[0159] Supply of polishing composition: flow casting

[0160] Supply amount of polishing composition: 200 ml / minute

[0161] [Amount of recess]

[0162] The amount of recess was judged according to the following 4-level judging criteria. Δχ is practically unacceptable. The results are shown in Table 1.

[0163] ◎: less than 15 nm

[0164] O: 15 nm or more and less than 30 nm

[0165] Δ: 30 nm or more and less than 50 nm

[0166] X: 50 nm or more

[0167] [Residual polysilicon (polishing residual)]

[0168] The film thickness of the polysilicon remaining on the P-TEOS film after polishing was measured using an optical film thickness meter (ASET-f5x: manufactured by KLA-Tencor). The film thickness at this time was taken as the polishing residue, and was judged by the following 4-grade judgment criteria. ΔX is not practically acceptable. The results are shown in Table 1.

[0169]

[0170]

[0171]

[0172]

[0173] [Measurement of Metal Impurities]

[0174] The P-TEOS film-coated silicon wafer after polishing was cleaned in a cleaning section while applying deionized water (DIW) using a PVA brush for 60 seconds. Then, it was dried for 30 seconds using a spin dryer. The concentrations of Na, K, and Li on the surface of the cleaned wafer were measured using a total reflection fluorescence X-ray device (device name: TREX-610T) manufactured by TECHNOS Corporation. The results are shown in Table 1.

[0175] [Table 1]

[0176]

[0177] [Investigation]

[0178] The polishing composition of the examples was able to reduce the remaining polysilicon that should be polished, and also to suppress dishing. In contrast, the polishing composition of the comparative examples produced remaining polysilicon that should be polished, or dishing was promoted, as shown in Table 1. Figures 3-5

[0179] The polishing composition of Example 1 had the best results among all the examples.

[0180] When polishing was performed using the polishing compositions of Example 2 and Example 5, the remaining film of polysilicon was slightly thick or a little dishing was produced. From these results, it was found that the number of silanol groups of the abrasive particles (colloidal silica) is preferably more than 6.6 / nm 2 and less than 17.5 / nm 2 . In addition, it was found that the average primary particle diameter of the abrasive particles (colloidal silica) is preferably more than 70 nm and less than 100 nm.

[0181] ​​​​​​​​When polishing was performed using the polishing composition of Example 3, the residual amount of sodium as a metal impurity was slightly large. When polishing was performed using the polishing composition of Example 4, the selectivity was slightly small, and in addition, a slight recess was generated. When polishing was performed using the polishing composition of Example 8, the residual amount of lithium as a metal impurity was slightly large. These results indicated that potassium hydroxide is suitable as an alkali metal salt.

[0182] When polishing was performed using the polishing composition of Example 6, the residual film of polysilicon was slightly thick, and in addition, a slight recess was generated. When polishing was performed using the polishing composition of Example 7, a slight recess was generated. These results suggested that it is appropriate that the pH of the polishing composition exceeds 9.5 and is lower than 11.

[0183] This application is based on Japanese Patent Application No. 2023-166812 filed on September 28, 2023, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A polishing composition, which is a polishing composition comprising colloidal silica, an alkali metal salt, and water, the pH of which is more than 9.5 and less than 11, the silanol group number of the colloidal silica being more than 6.6 / nm 2 and less than 17.5 / nm 2 wherein, The polishing composition is used in a process of polishing a second layer to expose a first layer in a polishing object having the first layer selected from a layer having an oxygen-silicon bond or a layer having a nitrogen-silicon bond and the second layer formed so as to fill a recess provided in the first layer, the second layer having a silicon-silicon bond, the polishing rate of the second layer being 20 to 40 relative to the polishing rate of the first layer.

2. A polishing composition, which is a polishing composition containing colloidal silica, an alkali metal salt, and water, having a pH of more than 9.5 and less than 11, and having a transmittance of more than 0.1% and less than 1% when light having a wavelength of 450 nm is transmitted in a case where the concentration of the colloidal silica is 1.5% by mass, wherein the average primary particle diameter of the colloidal silica is more than 70 nm and less than 100 nm. (i) the colloidal silica has a silanol group number of more than 6.6 per nm 2 and less than 17.5 per nm 2 ; or (ii) the silanol group number of the colloidal silica is more than 6.6 / nm 2 and less than 17.5 / nm 2 and the polishing composition is used in a process of polishing a second layer to expose a first layer in a polishing object having the first layer selected from a layer having an oxygen-silicon bond or a layer having a nitrogen-silicon bond and the second layer having a silicon-silicon bond, the first layer being provided with a recess and the second layer being formed so as to fill the recess.

3. A polishing composition consisting essentially of colloidal silica having a silanol group number of more than 6.6 / nm 2 and less than 17.5 / nm 2 , an alkali metal salt, and water, the pH of the polishing composition being more than 9.5 and less than 11.

4. A polishing composition consisting essentially of colloidal silica having a silanol group number of more than 6.6 / nm 2 and less than 17.5 / nm 2 , an alkali metal salt, a preservative, and water, the pH of the polishing composition being more than 9.5 and less than 11.

5. The polishing composition according to any one of claims 1 to 4, wherein, The colloidal silicon dioxide has a pulse NMR specific surface area of 40 m 2 / g or less.

6. The polishing composition according to any one of claims 1 to 4, wherein The alkali metal salt is a hydroxide of an alkali metal.

7. The polishing composition according to any one of claims 1 to 4, wherein The hydroxide of the alkali metal is potassium hydroxide.

8. The polishing composition according to claim 7, wherein, 9. The polishing composition according to claim 1 or 2, which does not substantially contain at least any one of HEC, PAA, POE lauryl ether, DBS, H2O2, ammonia, and amine.

10. The polishing composition according to claim 1 or 2, which does not substantially contain at least any one of a water-soluble polymer, a surfactant, an oxidizing agent, and a compound having a nitrogen atom. ​

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