JP2016003278A - Polishing liquid, polishing liquid set, and method for polishing substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid capable of polishing an insulating material at a high polishing speed and sufficiently suppressing the polishing speed of a stopper material.SOLUTION: The polishing liquid contains a liquid medium, abrasive grains containing a hydroxide of a tetravalent metal element, a polyoxyalkylene compound, a cationic polymer, and a ≥4C alcohol. The hydroxide of the tetravalent metal element is at least one selected from the group consisting of hydroxides of rare earth metal elements and a hydroxide of zirconium. The content of the polyoxyalkylene compound is 0.02 mass% or more based on the total mass of the polishing liquid.

Description

  The present invention relates to a polishing liquid, a polishing liquid set, and a method for polishing a substrate. In particular, the present invention relates to a polishing liquid, a polishing liquid set, and a substrate polishing method used in a substrate surface flattening process, which is a semiconductor element manufacturing technique. More specifically, the present invention relates to a polishing liquid and a polishing liquid set used in a planarization process of a shallow trench isolation (shallow trench isolation, hereinafter referred to as “STI”) insulating material, premetal insulating material, interlayer insulating material, and the like. And a method for polishing a substrate.

  In recent semiconductor device manufacturing processes, the importance of processing technology for higher density and miniaturization is increasing. CMP (Chemical Mechanical Polishing), which is one of the processing techniques, is used to form STI, planarize premetal insulating material or interlayer insulating material, plug or embedded metal wiring in the manufacturing process of semiconductor devices. This technology is essential for formation.

  The polishing liquid generally contains abrasive grains. As abrasive grains, silica (silicon oxide) particles such as fumed silica and colloidal silica, alumina (aluminum oxide) particles, ceria (cerium oxide) particles, and the like are known.

  By the way, in recent years, in the manufacturing process of a semiconductor element, it has been required to achieve further miniaturization of wiring, and polishing scratches generated during polishing have become a problem. To solve this problem, polishing liquids using hydroxide particles of tetravalent metal elements have been studied (for example, see Patent Documents 1 to 3 below). In addition, a method for producing hydroxide particles of a tetravalent metal element has been studied (see, for example, Patent Documents 4 and 5 below). These techniques try to reduce polishing scratches caused by particles by making the mechanical action as small as possible while taking advantage of the chemical action of the hydroxide particles of the tetravalent metal element.

International Publication No. 2002/067309 International Publication No. 2012/070541 International Publication No. 2012/070542 JP 2006-249129 A International Publication No. 2012/070544

Complete Collection of Distributed Technology, Information Organization Co., Ltd., July 2005, Chapter 3, “Latest Development Trends and Selection Criteria for Various Dispersers”

  In a CMP process or the like for forming STI, it is common to provide a stopper (for example, a stopper film, also referred to as a “polishing stop layer”) on a convex portion of a substrate having a concavo-convex pattern. Specifically, a laminate having a substrate having a concavo-convex pattern, a stopper disposed on a convex portion of the substrate, and an insulating material disposed on the substrate and the stopper so as to fill the concave portion is polished. Then, unnecessary portions of the insulating material are removed. This is because it is difficult to control the amount of polishing of the insulating material (the amount by which the insulating material is removed), and the degree of polishing is controlled by polishing the insulating material until the stopper is exposed. In this case, if the polishing of the stopper can be suppressed as much as possible, the polishing stops when the polishing progresses and the stopper is exposed, and the stopper and the insulating material embedded in the recess are prevented from being excessively polished. Can do.

  Conversely, if polishing of the stopper is not sufficiently suppressed, it is difficult to stop polishing when the stopper is exposed, and polishing proceeds excessively. As a result, a difference occurs in the thickness of the element isolation insulating material (insulating material filling the recess) and the thickness of the stopper, which may result in a defective product. Therefore, in the CMP process for forming the STI, the higher the ability to suppress the polishing of the stopper, the better, and there is a demand for a polishing liquid that can increase the ability to suppress the polishing rate. Generally, silicon nitride or polysilicon is used as a stopper material in the CMP process for forming the STI.

  A conventional polishing liquid using hydroxide particles of a tetravalent metal element has an advantage that it can suppress the generation of polishing flaws while having a good polishing rate for an insulating material. On the other hand, it is relatively difficult to suppress the polishing rate of the stopper material. For example, a polishing liquid using hydroxide particles of a tetravalent metal element tends to increase the polishing rate of the insulating material to be removed by increasing the pH, but at the same time up to the polishing rate of the stopper material It can be expensive.

  The present invention is intended to solve the above-described problem, and in a polishing liquid using abrasive grains containing a hydroxide of a tetravalent metal element, an insulating material can be polished at a high polishing rate, and a stopper material An object of the present invention is to provide a polishing liquid, a polishing liquid set, and a substrate polishing method capable of sufficiently suppressing the polishing rate.

  The present inventor has found that the above problem can be solved by using an alcohol having 4 or more carbon atoms as a polishing inhibitor for a stopper material.

  The polishing liquid according to the present invention contains a liquid medium, abrasive grains containing a tetravalent metal element hydroxide, a polyoxyalkylene compound, a cationic polymer, and an alcohol having 4 or more carbon atoms.

  According to the polishing liquid of the present invention, the insulating material can be polished at a high polishing rate, and the polishing rate of the stopper material can be sufficiently suppressed. According to such a polishing liquid, the polishing selectivity of the insulating material with respect to the stopper material can be improved. Further, according to the polishing liquid according to the present invention, these insulating materials can be highly planarized in the CMP technique for planarizing the shallow trench isolation insulating material, the premetal insulating material, the interlayer insulating material, and the like. According to the polishing liquid of the present invention, the insulating material can be polished with low polishing scratches while the insulating material is highly planarized.

  The tetravalent metal element hydroxide is preferably at least one selected from the group consisting of rare earth metal hydroxides and zirconium hydroxides. Thereby, generation | occurrence | production of the grinding | polishing damage | wound in a to-be-polished surface can further be suppressed, suppressing the polishing rate of stopper material.

  The content of the polyoxyalkylene compound is preferably 0.02% by mass or more based on the total mass of the polishing liquid. As a result, the insulating material can be easily polished at a high polishing rate, and the generation of polishing flaws on the surface to be polished can be further suppressed while suppressing the polishing rate of the stopper material. In addition, the solubility of alcohol having 4 or more carbon atoms in a solvent can be improved.

  The cationic polymer is preferably at least one selected from the group consisting of allylamine polymers, diallylamine polymers, vinylamine polymers, and ethyleneimine polymers. As a result, the insulating material can be easily polished at a high polishing rate, and the polishing rate of the stopper material can be sufficiently suppressed.

The alcohol having 4 or more carbon atoms is preferably a monohydric alcohol.
Further, the alcohol having 4 or more carbon atoms is preferably 0.01% by mass or more, more preferably 0.01% by mass or more and 10% by mass or less based on the total mass of the polishing liquid. By being 0.01 mass% or more, the polishing rate of the stopper material can be sufficiently suppressed while maintaining a high polishing rate of the insulating material.

  Another aspect of the present invention relates to the use of the polishing liquid for polishing a surface to be polished containing silicon oxide. That is, the polishing liquid according to the present invention is preferably used for polishing a surface to be polished containing silicon oxide.

  In the polishing liquid set according to the present invention, the constituents of the polishing liquid are stored separately as a first liquid and a second liquid, and the first liquid includes abrasive grains and a liquid medium, and the second liquid Includes a polyoxyalkylene compound, a cationic polymer, an alcohol having 4 or more carbon atoms, and a liquid medium. According to the polishing liquid set concerning the present invention, the same effect as the polishing liquid concerning the present invention can be acquired.

  The substrate polishing method according to one aspect of the present invention may include a step of polishing a surface to be polished of the substrate using the polishing liquid, and the first liquid and the second liquid in the polishing liquid set You may provide the process of grind | polishing the to-be-polished surface of a base | substrate using the polishing liquid obtained by mixing these. According to these polishing methods, the same effects as the polishing liquid according to the present invention can be obtained by using the polishing liquid or the polishing liquid set.

  A substrate polishing method according to another aspect of the present invention is a method for polishing a substrate having an insulating material and polysilicon, and the insulating material is selectively polished with respect to polysilicon using the polishing liquid. A step of selectively polishing the insulating material with respect to polysilicon using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set. It may be. According to these polishing methods, by using the polishing liquid or the polishing liquid set, the same effect as the polishing liquid according to the present invention can be obtained when the insulating material is selectively polished with respect to polysilicon. be able to.

  Further, a method for polishing a substrate according to another aspect of the present invention is a method for polishing a substrate having an insulating material and silicon nitride, wherein the insulating material is selectively polished with respect to silicon nitride using the polishing liquid. A step of selectively polishing the insulating material with respect to silicon nitride using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set. It may be. According to these polishing methods, when the insulating material is selectively polished with respect to silicon nitride by using the polishing liquid or the polishing liquid set, the same effect as the polishing liquid according to the present invention is obtained. be able to.

  According to the present invention, an insulating material (for example, silicon oxide) can be polished at a high polishing rate, and a polishing liquid, a polishing liquid set, and a stopper material (for example, silicon nitride, polysilicon) can be sufficiently suppressed. A method for polishing a substrate can be provided. According to the present invention, the polishing selectivity of the insulating material with respect to the stopper material can be improved.

It is a schematic diagram which shows a mode that an abrasive grain aggregates when an additive is added. It is a schematic diagram which shows a mode that an abrasive grain aggregates when an additive is added.

  Hereinafter, a polishing liquid, a polishing liquid set, and a substrate polishing method using the same according to embodiments of the present invention will be described in detail.

<Definition>
In this specification, “abrasive liquid” is defined as a composition that touches a surface to be polished during polishing. The phrase “polishing liquid” itself does not limit the components contained in the polishing liquid. As will be described later, the polishing liquid according to the present embodiment contains abrasive grains. Abrasive grains are also referred to as “abrasive particles”, but are referred to herein as “abrasive grains”. Abrasive grains are generally solid particles, and the object to be removed is removed during polishing by the mechanical action of the abrasive grains and the chemical action of the abrasive grains (mainly the surface of the abrasive grains). However, it is not limited to this.

<Polishing liquid>
The polishing liquid according to this embodiment is, for example, a polishing liquid for CMP. Specifically, the polishing liquid according to the present embodiment includes a liquid medium, abrasive grains containing a hydroxide of a tetravalent metal element, a polyoxyalkylene compound, a cationic polymer, and an alcohol having 4 or more carbon atoms. And containing.

  The essential components and components that can be optionally added are described below.

(Abrasive grains)
The abrasive grains are characterized by containing a hydroxide of a tetravalent metal element. The “tetravalent metal element hydroxide” as used herein is a compound containing a tetravalent metal (M ⁴⁺ ) and at least one hydroxide ion (OH ⁻ ). The hydroxide of a tetravalent metal element may contain anions other than hydroxide ions (for example, nitrate ions NO ₃ ⁻ and sulfate ions SO ₄ ²⁻ ). For example, a hydroxide of a tetravalent metal element may contain an anion (for example, nitrate ion NO ₃ ⁻ , sulfate ion SO ₄ ²⁻ ) bonded to the tetravalent metal element.

  Abrasive grains containing tetravalent metal element hydroxide are more reactive with insulating materials (eg, silicon oxide) than conventional abrasive grains made of silica, ceria, etc. Can be polished. In the polishing liquid according to this embodiment, other abrasive grains may be used in combination with the abrasive grains containing a hydroxide of a tetravalent metal element. Examples of such other abrasive grains include particles of silica, alumina, ceria, and the like. Further, as the abrasive grains containing a tetravalent metal element hydroxide, composite particles containing a tetravalent metal element hydroxide and silica can be used.

  In the abrasive grains, the content of the tetravalent metal element hydroxide is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and 98% by mass or more based on the whole abrasive grain. Is particularly preferable, and 99% by mass or more is extremely preferable. From the viewpoint of easy preparation of the polishing liquid and further excellent polishing characteristics, the abrasive grains are composed of hydroxides of tetravalent metal elements (100% by mass of the abrasive grains are hydroxide particles of tetravalent metal elements). Most preferred).

  The tetravalent metal element hydroxide is preferably at least one selected from the group consisting of rare earth metal hydroxides and zirconium hydroxides. As the tetravalent metal element hydroxide, a rare earth metal element hydroxide is preferable from the viewpoint of further improving the polishing rate of the insulating material. Examples of the rare earth metal element capable of taking tetravalence include lanthanoids such as cerium, praseodymium, and terbium. Among them, lanthanoids are preferable and cerium is more preferable in terms of further improving the polishing rate of the insulating material. A rare earth metal hydroxide and a zirconium hydroxide may be used in combination, or two or more rare earth metal hydroxides may be selected and used.

  From the viewpoint of further improving the polishing rate of the insulating material, the lower limit of the average particle size of the abrasive grains in the slurry in the polishing liquid or the polishing liquid set described below is preferably 1 nm or more, more preferably 2 nm or more, and 3 nm or more. Further preferred is 5 nm or more. The upper limit of the average particle size of the abrasive grains is preferably 300 nm or less, more preferably 250 nm or less, further preferably 200 nm or less, particularly preferably 100 nm or less, and particularly preferably 50 nm or less, from the viewpoint of further suppressing the surface to be polished from being scratched. Is very preferred. From the above viewpoint, the average grain size of the abrasive grains is more preferably 1 nm or more and 300 nm or less.

  The “average particle diameter” of the abrasive grains means the average secondary particle diameter of the abrasive grains. The average particle size of the abrasive grains is, for example, a light diffraction scattering type particle size distribution meter (for example, manufactured by Beckman Coulter, Inc., trade name: N5 or manufactured by Malvern Instruments Co., Ltd.) for a slurry in a polishing liquid or a polishing liquid set described later. , Trade name: Zetasizer 3000HSA).

  In the constituents of the polishing liquid according to this embodiment, the hydroxide of a tetravalent metal element is considered to have a great influence on the polishing characteristics. Therefore, by adjusting the content of the hydroxide of the tetravalent metal element, the chemical interaction between the abrasive grains and the surface to be polished can be improved, and the polishing rate can be further improved. From this, the content of the hydroxide of the tetravalent metal element is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and more preferably 0.03% by mass or more based on the total mass of the polishing liquid. 0.05% by mass or more is particularly preferable. The hydroxide content of the tetravalent metal element makes it easy to avoid agglomeration of the abrasive grains and improves the chemical interaction with the surface to be polished, effectively utilizing the characteristics of the abrasive grains. In view of the capability, it is preferably 8% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, particularly preferably 1% by mass or less, and particularly preferably 0.5% by mass or less. 0.3 mass% or less is very preferable.

  The lower limit of the abrasive content is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, based on the total mass of the polishing liquid, from the viewpoint of further improving the polishing rate of the insulating material. 02 mass% or more is still more preferable, 0.03 mass% or more is especially preferable, 0.04 mass% or more is very preferable, and 0.05 mass% or more is very preferable. The upper limit of the abrasive content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of increasing the storage stability of the polishing liquid. preferable. From the above viewpoint, the content of the abrasive grains is more preferably 0.005% by mass or more and 20% by mass or less based on the total mass of the polishing liquid.

  Further, it is preferable in that the cost and polishing scratches can be further reduced by further reducing the content of abrasive grains. When the content of abrasive grains decreases, the polishing rate of insulating materials and the like also tends to decrease. On the other hand, abrasive grains containing a hydroxide of a tetravalent metal element can obtain a predetermined polishing rate even with a small amount, so that the balance between the polishing rate and the advantage of reducing the content of abrasive grains is balanced. Further, the content of abrasive grains can be further reduced. From such a viewpoint, the content of the abrasive grains is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, particularly preferably 0.5% by mass or less, and 0.3% by mass. % Or less is very preferable.

[Absorbance]
The abrasive preferably contains a hydroxide of a tetravalent metal element and satisfies at least one of the following conditions (a) and (b). The “aqueous dispersion” in which the content of abrasive grains is adjusted to a predetermined amount means a liquid containing a predetermined amount of abrasive grains and water.
(A) Abrasive grains give an absorbance of 1.00 or more to light having a wavelength of 400 nm in an aqueous dispersion in which the content of the abrasive grains is adjusted to 1.0 mass%.
(B) The abrasive gives an absorbance of 1.000 or more to light having a wavelength of 290 nm in an aqueous dispersion in which the content of the abrasive is adjusted to 0.0065% by mass.

Regarding the condition (a), the polishing rate is further improved by using abrasive grains that give an absorbance of 1.00 or more with respect to light having a wavelength of 400 nm in an aqueous dispersion in which the content of abrasive grains is adjusted to 1.0 mass%. be able to. Although this reason is not necessarily clear, this inventor thinks as follows. That is, depending on the production conditions of the tetravalent metal element hydroxide, the tetravalent metal (M ⁴⁺ ), 1 to 3 hydroxide ions (OH ⁻ ), and 1 to 3 anions (X ^c- ) containing M (OH) _a X _b (where a + b × c = 4) is considered to be produced as part of the abrasive grains (note that such particles are also “4”). Abrasive grains containing a hydroxide of a valent metal element). In M (OH) _a X _b , electron-withdrawing anions (X ^c− ) act to improve the reactivity of hydroxide ions, and the amount of M (OH) _a X _b increases. It is considered that the polishing rate is improved along with this. And since the particle | grains containing M (OH) _{a Xb} absorb the light of wavelength 400nm, since the abundance of M (OH) _{a Xb} increases and the light absorbency with respect to the light of wavelength 400nm becomes high, polishing rate Is thought to improve.

It is considered that abrasive grains containing a tetravalent metal element hydroxide may contain not only M (OH) _{a Xb} but also M (OH) ₄ , MO _{2 and the} like. Examples of the anion (X ^c− ) include NO ₃ ⁻ and SO ₄ ²⁻ .

The fact that the abrasive grains containing a hydroxide of a tetravalent metal element contain M (OH) _{a Xb} is that the abrasive grains are thoroughly washed with pure water and then subjected to FT-IR ATR (Fourier transform Infrared Spectrometer Attenuated Total). This can be confirmed by a method of detecting a peak corresponding to an anion (X ^c− ) by a reflection method or a Fourier transform infrared spectrophotometer total reflection measurement method. The presence of an anion (X ^c− ) can also be confirmed by XPS (X-ray Photoelectron Spectroscopy, X-ray photoelectron spectroscopy).

Here, it has been confirmed that the absorption peak at a wavelength of 400 nm of M (OH) _a X _b (for example, M (OH) ₃ X) is much smaller than the absorption peak at a wavelength of 290 nm described later. On the other hand, the present inventor examined the magnitude of the absorbance using an aqueous dispersion having an abrasive content of 1.0% by mass, which has a relatively large abrasive content and is easily detected with a large absorbance. It has been found that when an abrasive that gives an absorbance of 1.00 or more with respect to light having a wavelength of 400 nm is used in an aqueous dispersion, the effect of improving the polishing rate is excellent. In addition, since it is thought that the light absorbency with respect to the light of wavelength 400nm originates in an abrasive grain as above-mentioned, it replaces with the abrasive grain which gives the light absorbency 1.00 or more with respect to the light of wavelength 400nm, and with respect to the light of wavelength 400nm. In the polishing liquid containing a substance that gives an absorbance of 1.00 or more (for example, a yellow pigment component), it is difficult to obtain the above-described improvement effect of the polishing rate.

  The absorbance with respect to light having a wavelength of 400 nm is preferably 1.50 or more, more preferably 1.55 or more, and even more preferably 1.60 or more from the viewpoint of facilitating polishing of the insulating material at a further excellent polishing rate.

Regarding the condition (b), the polishing rate is further improved by using abrasive grains that give an absorbance of 1.000 or more with respect to light having a wavelength of 290 nm in an aqueous dispersion in which the content of abrasive grains is adjusted to 0.0065% by mass. be able to. Although this reason is not necessarily clear, this inventor thinks as follows. That is, a particle containing M (OH) _a X _b (for example, M (OH) ₃ X) generated according to the production conditions of a tetravalent metal element hydroxide has an absorption peak near the wavelength of 290 nm. For example, particles made of Ce ⁴⁺ (OH ⁻ ) ₃ NO ₃ ⁻ have an absorption peak at a wavelength of 290 nm. Therefore, it is considered that the polishing rate is improved as the abundance of M (OH) _{a Xb} increases and the absorbance to light having a wavelength of 290 nm increases.

  Here, the absorbance with respect to light in the vicinity of a wavelength of 290 nm tends to be detected as it exceeds the measurement limit. On the other hand, the present inventors examined the magnitude of absorbance using an aqueous dispersion having an abrasive content of 0.0065% by mass with a relatively small abrasive content and a low absorbance that is easily detected. It has been found that when an abrasive that gives an absorbance of 1.000 or more with respect to light having a wavelength of 290 nm is used in the aqueous dispersion, the effect of improving the polishing rate is excellent. Further, the present inventor has found that the higher the absorbance of abrasive grains with respect to light near a wavelength of 290 nm, the higher the absorbance of the abrasive grains is, apart from light near a wavelength of 400 nm, where the light-absorbing material tends to exhibit a yellow color. It has been found that the yellowness of the polishing liquid and the slurry using the abrasive grains becomes deeper, and that the polishing rate is improved as the yellowness of the polishing liquid and the slurry becomes darker. And this inventor is the light absorbency with respect to the light of wavelength 290nm in the aqueous dispersion whose abrasive grain content is 0.0065 mass%, and the light absorbency with respect to the light of wavelength 400nm in the aqueous dispersion whose abrasive grain content is 1.0 mass%. Was found to correlate.

  The lower limit of the absorbance with respect to light having a wavelength of 290 nm is more preferably 1.050 or more, further preferably 1.100 or more, particularly preferably 1.130 or more, from the viewpoint of polishing the insulating material at a further excellent polishing rate. 150 or more is very preferable. The upper limit of absorbance for light having a wavelength of 290 nm is not particularly limited, but is preferably 10.00, for example.

  When the abrasive that gives an absorbance of 1.00 or more with respect to light having a wavelength of 400 nm gives an absorbance of 1.000 or more with respect to light with a wavelength of 290 nm in an aqueous dispersion in which the content of the abrasive is adjusted to 0.0065% by mass. Can polish the insulating material at a further excellent polishing rate.

Further, hydroxides of tetravalent metal elements (for example, M (OH) _a X _b ) tend not to absorb light with a wavelength of 450 nm or more, particularly 450 to 600 nm. Therefore, from the viewpoint of polishing the insulating material at an excellent polishing rate by suppressing the adverse effect on polishing due to the inclusion of impurities, the abrasive grains have a content of 0.0065% by mass ( In an aqueous dispersion adjusted to 65 ppm, it is preferable to give an absorbance of 0.010 or less to light having a wavelength of 450 to 600 nm. That is, it is preferable that the light absorbency with respect to all the light in the wavelength range of 450-600 nm does not exceed 0.010 in the water dispersion liquid which adjusted content of the abrasive grain to 0.0065 mass%. The upper limit of the absorbance with respect to light having a wavelength of 450 to 600 nm is more preferably 0.005 or less, and further preferably 0.001 or less. The lower limit of the absorbance with respect to light having a wavelength of 450 to 600 nm is preferably 0.

  The absorbance in the aqueous dispersion can be measured using, for example, a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Specifically, for example, an aqueous dispersion in which the content of abrasive grains is adjusted to 1.0 mass% or 0.0065 mass% is prepared as a measurement sample. About 4 mL of this measurement sample is put into a 1 cm square cell, and the cell is set in the apparatus. Next, the absorbance is measured in the wavelength range of 200 to 600 nm, and the absorbance is determined from the obtained chart.

  If the absorbance is 1.00 or more when the absorbance for light with a wavelength of 400 nm is measured after being diluted excessively so that the content of the abrasive is less than 1.0% by mass, the content of the abrasive is The absorbance may be screened on the assumption that the absorbance is 1.00 or more even when the content is 1.0 mass%. If the absorbance is 1.000 or more when the absorbance for light having a wavelength of 290 nm is measured after being diluted excessively so that the content of the abrasive is less than 0.0065% by mass, the content of the abrasive is Even when the amount is 0.0065% by mass, the absorbance may be screened on the assumption that the absorbance is 1.000 or more. If the absorbance is 0.010 or less when the absorbance for light having a wavelength of 450 to 600 nm is measured by diluting the abrasive grain content to be greater than 0.0065% by mass, the abrasive grains are contained. Even when the amount is 0.0065% by mass, the absorbance may be screened on the assumption that the absorbance is 0.010 or less.

[Light transmittance]
The polishing liquid according to this embodiment preferably has high transparency to visible light (transparent or nearly transparent by visual observation). Specifically, the abrasive contained in the polishing liquid according to the present embodiment has a light transmittance of 50% with respect to light having a wavelength of 500 nm in an aqueous dispersion in which the content of the abrasive is adjusted to 1.0 mass%. / Cm or more is preferable. Thereby, since the fall of the grinding | polishing rate resulting from addition of an additive can be further suppressed, it becomes easy to acquire another characteristic, maintaining a grinding | polishing rate. From this viewpoint, the lower limit of the light transmittance is more preferably 60% / cm or more, further preferably 70% / cm or more, particularly preferably 80% / cm or more, extremely preferably 90% / cm or more, 92% / Cm or more is very preferable. The upper limit of the light transmittance is 100% / cm.

  The reason why the decrease in the polishing rate can be suppressed by adjusting the light transmittance of the abrasive grains in this way is not known in detail, but the present inventor thinks as follows. In abrasive grains containing a hydroxide of a tetravalent metal element (cerium or the like), it is considered that the chemical action is more dominant than the mechanical action. Therefore, it is considered that the number of abrasive grains contributes more to the polishing rate than the size of the abrasive grains.

  When the light transmittance is low in an aqueous dispersion having an abrasive grain content of 1.0 mass%, the abrasive grains present in the aqueous dispersion are particles having a large particle diameter (hereinafter referred to as “coarse particles”). It is considered that there are relatively many. When an additive (for example, polyvinyl alcohol (PVA)) is added to a polishing liquid containing such abrasive grains, as shown in FIG. 1, other particles aggregate with coarse particles as nuclei. As a result, the number of abrasive grains acting on the surface to be polished per unit area (the number of effective abrasive grains) is reduced, and the specific surface area of the abrasive grains in contact with the surface to be polished is reduced. Conceivable.

  On the other hand, when the light transmittance is high in an aqueous dispersion having an abrasive grain content of 1.0 mass%, it is considered that the abrasive grains present in the aqueous dispersion are in a state of less “coarse particles”. When the abundance of coarse particles is small in this way, as shown in FIG. 2, even if an additive (for example, polyvinyl alcohol) is added to the polishing liquid, there are few coarse particles that become the core of aggregation. Aggregation between the grains is suppressed, or the size of the aggregated particles is smaller than that of the aggregated particles shown in FIG. As a result, the number of abrasive grains (number of effective abrasive grains) acting on the surface to be polished per unit area is maintained, and the specific surface area of the abrasive grains in contact with the surface to be polished is maintained. It is considered to be.

  According to the inventor's study, even a polishing liquid having the same particle diameter measured by a general particle size measuring device is visually transparent (high light transmittance) and visually turbid. It has been found that there can be (low light transmittance). From this, it is considered that the coarse particles capable of causing the above-described action contribute to the reduction of the polishing rate even if the amount is so small that it cannot be detected by a general particle size measuring apparatus.

  In addition, even if filtration is repeated a plurality of times to reduce coarse particles, the phenomenon that the polishing rate decreases due to the additive does not improve so much, and the improvement effect of the polishing rate due to absorbance may not be sufficiently exhibited. I know. Then, this inventor discovered that the said problem can be solved by devising the manufacturing method of an abrasive grain etc. and using an abrasive grain with a high light transmittance in an aqueous dispersion.

  The light transmittance is a transmittance for light having a wavelength of 500 nm. The light transmittance can be measured with a spectrophotometer. Specifically, for example, it can be measured with a spectrophotometer U3310 (device name) manufactured by Hitachi, Ltd.

  As a more specific measurement method, an aqueous dispersion in which the content of abrasive grains is adjusted to 1.0% by mass is prepared as a measurement sample. About 4 mL of this measurement sample is put into a 1 cm square cell, and the measurement is performed after setting the cell in the apparatus. In addition, when the content of the abrasive grains is 50% / cm or more in an aqueous dispersion having a content of greater than 1.0% by mass, the light transmittance is also obtained when this is diluted to 1.0% by mass. Is apparently 50% / cm or more. Therefore, the light transmittance can be screened by a simple method by using an aqueous dispersion having an abrasive content greater than 1.0% by mass.

  The absorbance and light transmittance that the abrasive grains contained in the polishing liquid give in the aqueous dispersion are obtained by removing the solid components other than the abrasive grains and the liquid components other than water, and then the aqueous dispersion having a predetermined abrasive grain content. It can be prepared and measured using the aqueous dispersion. Although it depends on the components contained in the polishing liquid, the solid component or liquid component is removed by, for example, centrifugation using a centrifuge capable of applying a gravitational acceleration of several thousand G or less, or applying a gravitational acceleration of tens of thousands G or more. Such as ultracentrifugation using an ultracentrifuge; chromatography methods such as partition chromatography, adsorption chromatography, gel permeation chromatography, ion exchange chromatography; natural filtration, vacuum filtration, pressure filtration, limiting Filtration methods such as external filtration; distillation methods such as vacuum distillation and atmospheric distillation can be used, and these may be combined as appropriate.

  For example, when a compound having a weight average molecular weight of tens of thousands or more (for example, 50,000 or more) is included, a chromatography method, a filtration method and the like can be mentioned, and among these, gel permeation chromatography and ultrafiltration are preferable. When using the filtration method, the abrasive grains contained in the polishing liquid can pass through the filter by setting appropriate conditions. When a compound having a weight average molecular weight of tens of thousands or less (for example, less than 50,000) is used, examples thereof include a chromatography method, a filtration method, and a distillation method, and gel permeation chromatography, ultrafiltration, and vacuum distillation are preferable. When multiple types of abrasive grains are included, filtration methods, centrifugal separation methods and the like can be mentioned. In the case of filtration, in the filtrate, in the liquid phase, abrasive grains containing a hydroxide of a tetravalent metal element are included. More included.

  As a method for separating abrasive grains by a chromatography method, for example, an abrasive component can be fractionated and / or other components can be fractionated under the following conditions.

Sample solution: 100 μL of polishing liquid
Detector: UV-VIS detector manufactured by Hitachi, Ltd., trade name “L-4200”, wavelength: 400 nm
Integrator: GPC integrator manufactured by Hitachi, Ltd., trade name “D-2500”
Pump: Hitachi, Ltd., trade name “L-7100”
Column: Hitachi Chemical Co., Ltd. water-based HPLC packed column, trade name “GL-W550S”
Eluent: Deionized water Measurement temperature: 23 ° C
Flow rate: 1 mL / min (pressure is about 40-50 kg / cm ² )
Measurement time: 60 minutes

  In addition, it is preferable to deaerate the eluent using a deaeration device before performing chromatography. When the deaerator cannot be used, it is preferable to deaerate the eluent in advance with ultrasonic waves or the like.

  Depending on the components contained in the polishing liquid, it may not be possible to separate the abrasive components even under the above conditions.In that case, by optimizing the sample solution amount, column type, eluent type, measurement temperature, flow rate, etc. Can be separated. Further, by adjusting the pH of the polishing liquid, there is a possibility that the distillation time of the components contained in the polishing liquid can be adjusted and separated from the abrasive grains. When there are insoluble components in the polishing liquid, it is preferable to remove the insoluble components by filtration, centrifugation, or the like, if necessary.

[Production method of abrasive grains]
A hydroxide of a tetravalent metal element can be produced by reacting a salt of a tetravalent metal element (metal salt) with an alkali source (base). The hydroxide of the tetravalent metal element is preferably prepared by mixing a salt of the tetravalent metal element and an alkali solution (for example, an alkaline aqueous solution). Thereby, particles having an extremely fine particle diameter can be obtained, and a polishing liquid further excellent in the effect of reducing polishing scratches can be obtained. Such a method is disclosed in Patent Document 4, for example. A hydroxide of a tetravalent metal element can be obtained by mixing a metal salt solution of a salt of a tetravalent metal element (for example, an aqueous metal salt solution) and an alkali solution. In addition, when supplying at least one of the salt of a tetravalent metal element and an alkali source to a reaction system in a liquid state, the means to stir a liquid mixture is not limited. For example, a method of stirring a mixed solution using a bar-like, plate-like or propeller-like stirrer or a stirring blade that rotates around a rotation axis, a magnetic stirrer that transmits power from the outside of a container, and a rotating magnetic field Examples include a method of stirring the mixed solution by rotating a stirrer, a method of stirring the mixed solution with a pump installed outside the tank, and a method of stirring the mixed liquid by pressurizing the outside air and blowing it into the tank vigorously. As a salt of a tetravalent metal element, a conventionally known salt can be used without particular limitation, and M (NO ₃ ) ₄ , M (SO ₄ ) ₂ , M (NH ₄ ) ₂ (NO ₃ ) ₆ , M (NH _4). ) ₄ (SO ₄ ) ₄ (M represents a rare earth metal element), Zr (SO ₄ ) ₂ .4H ₂ O, and the like. M is preferably chemically active cerium (Ce).

  Examples of means for adjusting the absorbance and light transmittance include optimization of a method for producing a hydroxide of a tetravalent metal element. Specific examples of the method for changing the absorbance with respect to light having a wavelength of 400 nm and the absorbance with respect to light having a wavelength of 290 nm include selection of an alkali source in an alkali solution, adjustment of a raw material concentration in the metal salt solution and the alkali solution, and metal salt Adjustment of the mixing speed of a solution and an alkali liquid adjustment of the liquid temperature of the liquid mixture obtained by mixing the salt of a tetravalent metal element and an alkali source is mentioned. Further, as a method of changing the light transmittance for light having a wavelength of 500 nm, specifically, for example, adjustment of the raw material concentration in the metal salt solution and the alkali liquid, adjustment of the mixing speed of the metal salt solution and the alkali liquid, and mixing Adjustment of the stirring speed when performing, adjustment of the liquid temperature of a liquid mixture is mentioned.

  In order to increase the absorbance with respect to light with a wavelength of 400 nm, the absorbance with respect to light with a wavelength of 290 nm, and the light transmittance with respect to light with a wavelength of 500 nm, the method for producing a hydroxide of a tetravalent metal element is made more “gradual”. It is preferable. Here, “slow” means that the increase in pH when the pH of the reaction system increases as the reaction proceeds is moderated (slowed). Conversely, in order to reduce the absorbance for light with a wavelength of 400 nm, the absorbance for light with a wavelength of 290 nm, and the light transmittance for light with a wavelength of 500 nm, the method for producing a hydroxide of a tetravalent metal element is more “violently”. Is preferred. Here, “violently” means that the increase in pH when the pH of the reaction system increases as the reaction progresses is increased (accelerated). In order to adjust these values of absorbance and light transmittance to a predetermined range, it is preferable to optimize the method for producing a hydroxide of a tetravalent metal element with reference to the above tendency. Hereinafter, a method for controlling absorbance and light transmittance will be described in more detail.

{Alkali source}
A conventionally well-known thing can be especially used without a restriction | limiting as an alkali source in an alkali liquid. Examples of the alkali source include organic bases and inorganic bases. Organic bases include nitrogen-containing organic bases such as guanidine, triethylamine and chitosan; nitrogen-containing heterocyclic organic bases such as pyridine, piperidine, pyrrolidine and imidazole; ammonium carbonate, ammonium hydrogen carbonate, tetramethylammonium hydroxide (TMAH), water Examples thereof include ammonium salts such as tetraethylammonium oxide, tetramethylammonium chloride, and tetraethylammonium chloride. Examples of inorganic bases include inorganic salts of alkali metals such as ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, lithium hydrogen carbonate, sodium hydrogen carbonate, and potassium hydrogen carbonate. Etc. An alkali source can be used individually by 1 type or in combination of 2 or more types.

  As the alkali source, ammonia and imidazole are preferable and imidazole is more preferable from the viewpoint of further improving the polishing rate of the insulating material. In order to increase the absorbance with respect to light having a wavelength of 400 nm and the absorbance with respect to light having a wavelength of 290 nm, it is preferable to use an alkali source exhibiting weak basicity as the alkali source. Among the alkali sources, nitrogen-containing heterocyclic organic bases are preferable, pyridine, piperidine, pyrrolidine, and imidazole are more preferable, pyridine and imidazole are further preferable, and imidazole is particularly preferable.

{concentration}
By controlling the raw material concentrations in the metal salt solution and the alkali solution, the absorbance with respect to light having a wavelength of 400 nm, the absorbance with respect to light with a wavelength of 290 nm, and the light transmittance with respect to light with a wavelength of 500 nm can be changed. Specifically, the absorbance tends to increase by increasing the metal salt concentration of the metal salt solution, and the absorbance tends to increase by decreasing the alkali concentration (base concentration, alkali source concentration) of the alkali solution. There is. In addition, the light transmittance tends to increase by increasing the metal salt concentration, and the light transmittance tends to increase by decreasing the alkali concentration.

  The upper limit of the metal salt concentration in the metal salt solution is preferably 1.000 mol / L or less on the basis of the entire metal salt solution, in that it is easy to achieve both excellent polishing rate and excellent abrasive stability. More preferable is 500 mol / L or less, still more preferable is 0.300 mol / L or less, and particularly preferable is 0.200 mol / L or less. The lower limit of the metal salt concentration can suppress the rapid reaction (can moderate the rise in pH), absorbs light with a wavelength of 400 nm, absorbs light with a wavelength of 290 nm, and transmits light with a wavelength of 500 nm. In terms of increasing the rate, it is preferably 0.010 mol / L or more, more preferably 0.020 mol / L or more, and further preferably 0.030 mol / L or more, based on the entire metal salt solution.

  The upper limit of the alkali concentration in the alkali solution is preferably 15.0 mol / L or less, more preferably 12.0 mol / L or less, and more preferably 10.0 mol based on the whole alkali solution in terms of suppressing the rapid reaction. / L or less is more preferable, and 5.0 mol / L or less is particularly preferable. The lower limit of the alkali concentration is not particularly limited, but from the viewpoint of productivity, 0.001 mol / L or more is preferable based on the entire alkali solution.

  It is preferable that the alkali concentration in the alkaline solution is appropriately adjusted depending on the selected alkali source. For example, in the case of an alkali source in which the pKa of the conjugate acid of the alkali source is 20 or more, the upper limit of the alkali concentration is 0.10 mol / L or less based on the whole of the alkali solution in terms of suppressing a rapid reaction. Is preferable, 0.05 mol / L or less is more preferable, and 0.01 mol / L or less is still more preferable. The lower limit of the alkali concentration is not particularly limited, but is 0.001 mol / L or more based on the total amount of the alkali solution in terms of suppressing the use amount of the solution used for obtaining a predetermined amount of tetravalent metal element hydroxide. preferable.

  In the case of an alkali source in which the pKa of the conjugate acid of the alkali source is 12 or more and less than 20, the upper limit of the alkali concentration is 1.0 mol / L or less on the basis of the entire alkali solution in terms of suppressing a rapid reaction. Is preferably 0.50 mol / L or less, more preferably 0.10 mol / L or less. The lower limit of the alkali concentration is not particularly limited, but is 0.01 mol / L or more based on the total amount of the alkali solution in terms of suppressing the amount of the solution used for obtaining a predetermined amount of tetravalent metal element hydroxide. preferable.

  In the case of an alkali source in which the pKa of the conjugate acid of the alkali source is less than 12, the upper limit of the alkali concentration is preferably 15.0 mol / L or less on the basis of the entire alkali solution, in order to suppress rapid reaction. 10.0 mol / L or less is more preferable, and 5.0 mol / L or less is still more preferable. The lower limit of the alkali concentration is not particularly limited, but is 0.10 mol / L or more based on the total amount of the alkali solution in terms of suppressing the amount of the solution used for obtaining a predetermined amount of the tetravalent metal element hydroxide. preferable.

  Examples of the alkali source in which the pKa of the conjugate acid of the alkali source is 20 or more include 1,8-diazabicyclo [5.4.0] undec-7-ene (pKa: 25). Examples of the alkali source in which the pKa of the conjugate acid of the alkali source is 12 or more and less than 20 include potassium hydroxide (pKa: 16) and sodium hydroxide (pKa: 13). Examples of the alkali source in which the pKa of the conjugate acid of the alkali source is less than 12 include ammonia (pKa: 9) and imidazole (pKa: 7). The pKa value of the conjugate acid of the alkali source used is not particularly limited as long as the alkali concentration is appropriately adjusted, but the pKa of the conjugate acid of the alkali source is preferably less than 20, preferably less than 12. Is more preferably less than 10, and particularly preferably less than 8.

{Mixing speed}
By controlling the mixing speed of the metal salt solution and the alkali solution, the absorbance with respect to light with a wavelength of 400 nm, the absorbance with respect to light with a wavelength of 290 nm, and the light transmittance with respect to light with a wavelength of 500 nm can be changed. As a tendency, the absorbance and the light transmittance are increased by making the increase in pH gentle (slow). More specifically, the absorbance tends to increase by reducing the mixing speed, and the absorbance tends to decrease by increasing the mixing speed. Moreover, there exists a tendency for the light transmittance to become high by making a mixing speed slow, and there exists a tendency for the light transmittance to become low by making a mixing speed fast.

The upper limit of the mixing speed is preferably 5.00 × 10 ⁻³ m ³ / min (5 L / min) or less from the viewpoint of further suppressing the rapid progress of the reaction and further suppressing the local reaction bias. 1.00 × 10 ⁻³ m ³ / min (1 L / min) or less, more preferably 5.00 × 10 ⁻⁴ m ³ / min (500 mL / min) or less, and 1.00 × 10 ^−4. m ³ / min (100 mL / min) or less is particularly preferable. The lower limit of the mixing speed is not particularly limited, but is preferably 1.00 × 10 ⁻⁷ m ³ / min (0.1 mL / min) or more from the viewpoint of productivity.

{Stirring speed}
By controlling the stirring speed when mixing the metal salt solution and the alkali solution, the light transmittance with respect to light having a wavelength of 500 nm can be changed. Specifically, the light transmittance tends to increase by increasing the stirring speed, and the light transmittance tends to decrease by decreasing the stirring speed.

The lower limit of the stirring speed can further suppress the deviation of the response in the local, and, from the viewpoint of excellent mixing efficiency, preferably 30min ^-1 or more, more preferably 50min ^-1 or more, 80min ^-1 or more is more preferable. The upper limit of the stirring speed is not particularly limited and needs to be adjusted as appropriate depending on the size and shape of the stirring blade, but is preferably 1000 min ⁻¹ or less from the viewpoint of suppressing liquid splashing.

{Liquid temperature (synthesis temperature)}
By controlling the liquid temperature of the mixture obtained by mixing a salt of a tetravalent metal element and an alkali source, the absorbance for light with a wavelength of 400 nm, the absorbance for light with a wavelength of 290 nm, and the light transmittance for light with a wavelength of 500 nm are obtained. Abrasive grains that can be changed and can achieve a desired polishing rate and storage stability can be obtained. Specifically, the absorbance tends to increase by lowering the liquid temperature, and the absorbance tends to decrease by increasing the liquid temperature. Moreover, the light transmittance tends to increase by lowering the liquid temperature, and the light transmittance tends to decrease by increasing the liquid temperature.

  Liquid temperature is the temperature in the liquid mixture which can be read, for example by installing a thermometer in a liquid mixture, and it is preferable that it is 0-100 degreeC. The upper limit of the liquid temperature is preferably 100 ° C. or less, more preferably 60 ° C. or less, still more preferably 55 ° C. or less, particularly preferably 50 ° C. or less, and particularly preferably 45 ° C. or less in that rapid reaction can be suppressed. preferable. The lower limit of the liquid temperature is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, and still more preferably 20 ° C. or higher in that the reaction can be easily advanced.

  The tetravalent metal element hydroxide synthesized by the above method may contain impurities (for example, metal impurities), but the impurities can be removed by washing. For washing the tetravalent metal element hydroxide, a method of repeating solid-liquid separation several times by centrifugation or the like can be used. Further, it can be washed by centrifugation, dialysis, ultrafiltration, removal of ions by an ion exchange resin or the like. By removing the impurities, the absorbance with respect to light having a wavelength of 450 to 600 nm can be adjusted.

  When the abrasive grains obtained above are agglomerated, they can be dispersed in water by an appropriate method. As a method for dispersing abrasive grains in water, which is the main dispersion medium, mechanical dispersion treatment using a homogenizer, an ultrasonic disperser, a wet ball mill, or the like may be used in addition to the dispersion treatment using a stirrer. For the dispersion method and the particle size control method, for example, the method described in Non-Patent Document 1 can be used. The dispersibility of the abrasive grains can also be improved by performing the above-described cleaning treatment to lower the electrical conductivity of the dispersion liquid containing abrasive grains (for example, 500 mS / m or less). Therefore, the cleaning process may be applied as a dispersion process, and the cleaning process and the dispersion process may be used in combination.

(Additive)
The polishing liquid according to this embodiment contains an additive. Here, “additive” means polishing other than the liquid medium and abrasive grains in order to adjust polishing characteristics such as polishing rate and polishing selectivity; polishing liquid characteristics such as abrasive dispersibility and storage stability. It refers to the substance contained in the liquid.

[First additive]
The abrasive | polishing agent which concerns on this embodiment contains a polyoxyalkylene compound as a 1st additive. The first additive has an effect of suppressing an excessive increase in the polishing rate for the stopper film (for example, a polysilicon film). Further, by using the first additive, high flatness can be obtained by suppressing polishing of the insulating film (for example, a silicon oxide film) after the stopper film is exposed. It is presumed that when the polyoxyalkylene compound covers the insulating film and the stopper film, the progress of polishing by the abrasive grains is alleviated and the polishing rate is prevented from becoming excessively high.

  Examples of the polyoxyalkylene compound include polyalkylene glycol and polyoxyalkylene derivatives.

  Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polybutylene glycol and the like. The polyalkylene glycol is preferably at least one selected from the group consisting of polyethylene glycol and polypropylene glycol, and more preferably polyethylene glycol.

  The polyoxyalkylene derivative is a compound in which a functional group or a substituent is introduced into polyalkylene glycol, or a compound in which three or less polyalkylene oxides are added to an organic compound. Examples of the functional group and substituent include alkyl ether, alkylphenyl ether, phenyl ether, styrenated phenyl ether, alkylamine, fatty acid ester, and glycol ester. Examples of the polyoxyalkylene derivatives include polyoxyethylene alkyl ethers (for example, Kao's Emulgen series), polyoxyethylene alkyl phenyl ethers (for example, Daigen Kogyo's Neugen EA series), polyoxyethylene sorbitan fatty acid esters (Eg, Daiichi Kogyo Seiyaku, Sorgen TW series), polyoxyethylene fatty acid esters (eg, Kao, Emanon series), polyoxyethylene alkylamines (eg, Daiichi Kogyo Seiyaku, Amiradin D), etc. Examples include compounds to which 3 or less polyalkylene oxides are added (for example, manufactured by Nissin Chemical Industry Co., Ltd., Surfynol 465, manufactured by Nippon Emulsifier Co., Ltd., TMP series) and the like.

  In the polishing agent according to this embodiment, the polyoxyalkylene compound can be used alone or in combination of two or more for the purpose of adjusting polishing properties such as polishing selectivity and flatness.

The polymerization average molecular weight of the first additive is not particularly limited, but from the viewpoint of workability and foamability, the upper limit is preferably 100,000 or less, more preferably 50000 or less, still more preferably 10,000 or less, and further preferably 5000 or less. Particularly preferred is 3000 or less. The lower limit of the polymerization average molecular weight of the first additive is preferably 200 or more, more preferably 400 or more, and still more preferably 500 or more, from the viewpoint of further improving polishing selectivity and flatness. In addition, a weight average molecular weight can be measured on condition of the following by the gel permeation chromatography method (GPC) using the calibration curve of a standard polystyrene, for example.
Equipment used: Hitachi L-6000 (manufactured by Hitachi, Ltd.)
Column: gel pack GL-R420 + gel pack GL-R430 + gel pack GL-R
440 [Hitachi Chemical Co., Ltd., trade name, total of 3]
Eluent: Tetrahydrofuran Measurement temperature: 40 ° C
Flow rate: 1.75 ml / min.
Detector: L-3300RI [manufactured by Hitachi, Ltd.]

  The lower limit of the content of the polyoxyalkylene compound (first additive) is preferably 0.01% by mass or more based on the total mass of the polishing agent from the viewpoint of further improving polishing selectivity and flatness. 02 mass% or more is more preferable, 0.1 mass% or more is still more preferable, and 0.3 mass% or more is especially preferable. From the viewpoint of obtaining an appropriate polishing rate, the upper limit of the content of the polyoxyalkylene compound (first additive) is preferably 5% by mass or less, more preferably 2% by mass or less, based on the total mass of the abrasive. 1 mass% or less is still more preferable. In addition, when using a some compound as a polyoxyalkylene compound (1st additive), it is preferable that the sum total of content of each compound satisfy | fills the said range.

[Second additive: cationic polymer]
The polishing liquid according to the present embodiment contains a cationic polymer as a second additive in addition to the first additive (polyoxyalkylene compound). A “cationic polymer” is defined as a polymer having a cationic group or a group that can be ionized into a cationic group in the main chain or side chain. Examples of the cationic group include an amino group, an imino group, and a cyano group.

  The cationic polymer has an effect of further suppressing an excessive increase in the polishing rate of the stopper material when used in combination with the first additive. In addition, the cationic polymer can suppress a decrease in the polishing rate of the insulating material due to excessive coating of the insulating material with the first additive in addition to the stopper material, thereby improving the polishing rate of the insulating material. There is also an effect. Therefore, when the first additive and the cationic polymer are used in combination, the cationic polymer interacts with the first additive, so that the polishing rate of the stopper material can be suppressed, and the insulating material It is considered that the polishing rate can be improved.

  The cationic polymer can be obtained by polymerizing at least one monomer component selected from the group consisting of allylamine, diallylamine, vinylamine, ethyleneimine, and derivatives thereof. The cationic polymer is at least one selected from the group consisting of an allylamine polymer, a diallylamine polymer, a vinylamine polymer, and an ethyleneimine polymer.

  An allylamine polymer is a polymer obtained by polymerizing allylamine and its derivatives. Examples of the allylamine derivative include alkoxycarbonylated allylamine, methylcarbonylated allylamine, aminocarbonylated allylamine, ureated allylamine and the like.

  A diallylamine polymer is a polymer obtained by polymerizing diallylamine and its derivatives. Examples of diallylamine derivatives include methyl diallylamine, diallyldimethylammonium salt, diallylmethylethylammonium salt, acylated diallylamine, aminocarbonylated diallylamine, alkoxycarbonylated diallylamine, aminothiocarbonylated diallylamine, hydroxyalkylated diallylamine, and the like. Examples of the ammonium salt include ammonium chloride and ammonium alkyl sulfate (for example, ammonium ethyl sulfate).

  A vinylamine polymer is a polymer obtained by polymerizing vinylamine and its derivatives. Examples of the vinylamine derivative include alkylated vinylamine, amidated vinylamine, ethylene oxideated vinylamine, propylene oxided vinylamine, alkoxylated vinylamine, carboxymethylated vinylamine, acylated vinylamine, and ureaated vinylamine.

  The ethyleneimine polymer is a polymer obtained by polymerizing ethyleneimine and its derivatives. Examples of the ethyleneimine derivative include aminoethylated acrylic polymer, alkylated ethyleneimine, ureaated ethyleneimine, propylene oxideated ethyleneimine and the like.

  The cationic polymer may have structural units derived from monomer components other than allylamine, diallylamine, vinylamine, ethyleneimine, and derivatives thereof, such as acrylamide, dimethylacrylamide, diethylacrylamide, hydroxyethylacrylamide, acrylic acid. And may have a structural unit derived from methyl acrylate, methacrylic acid, maleic acid or sulfur dioxide.

  The cationic polymer may be a homopolymer of allylamine, diallylamine, vinylamine, or ethyleneimine (polyallylamine, polydiallylamine, polyvinylamine, polyethyleneimine), and is derived from allylamine, diallylamine, vinylamine, ethyleneimine, or derivatives thereof. A copolymer having the following structural unit may also be used. In the copolymer, the arrangement of structural units is arbitrary. For example, (a) a form of block copolymer in which the same type of structural units are continuous, (b) a form of random copolymerization in which the structural units A and B are particularly ordered, (c) structural units A and structural units It can take any form, including alternating copolymerization forms in which B are arranged alternately.

  The lower limit of the weight average molecular weight of the cationic polymer is preferably 100 or more, more preferably 300 or more, and even more preferably 500 or more, from the viewpoint of further improving the polishing selectivity of the insulating material with respect to the stopper material. The upper limit of the weight average molecular weight of the cationic polymer is preferably 1000000 or less, more preferably 600000 or less, and even more preferably 300000 or less, from the viewpoint of further improving the polishing selectivity of the insulating material with respect to the stopper material.

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

  From the viewpoint of further improving the polishing selectivity and flatness, the lower limit of the content of the cationic polymer is preferably 0.0001% by mass or more, more preferably 0.0002% by mass or more based on the total mass of the polishing liquid. 0.0005% by mass or more is more preferable. From the viewpoint of further improving the polishing selectivity, the upper limit of the content of the cationic polymer is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less, based on the total mass of the polishing liquid. Preferably, 0.5 mass% or less is particularly preferable, 0.1 mass% or less is extremely preferable, 0.05 mass% or less is very preferable, and 0.01 mass% or less is particularly preferable. In addition, when using a some compound as a cationic polymer, it is preferable that the sum total of content of each compound satisfy | fills the said range. The content of the cationic polymer depends on the insulating material production method (type and filming conditions) from the viewpoint of further improving the polishing speed of the insulating material, the polishing selectivity of the insulating material with respect to the stopper material, and the flatness. It is preferable to adjust appropriately.

[Third additive: alcohol having 4 or more carbon atoms]
The polishing liquid according to the present embodiment contains an alcohol having 4 or more carbon atoms as a third additive in addition to the first additive (polyoxyalkylene compound) and the second additive (cationic polymer). To do.

  The alcohol having 4 or more carbon atoms has an effect of suppressing an excessive increase in the polishing rate when silicon nitride is used as the stopper material.

  The alcohol having 4 or more carbon atoms is preferably a monovalent alcohol. As monohydric alcohols, butanol (C4), pentyl alcohol (C5), hexanol (C6), heptanol (C7), octanol (C8) dodecanol (C12), stearyl alcohol (C18) and structural isomers thereof are used. Etc.

  The alcohol having 4 or more carbon atoms is preferably at least one selected from the group consisting of pentyl alcohol (C5), hexanol (C6), heptanol (C7), octanol (C8), and structural isomers thereof.

  From the viewpoint of further improving the polishing selectivity and flatness, the lower limit of the content of alcohol having 4 or more carbon atoms is preferably 0.01% by mass or more, and more preferably 0.1% by mass or more based on the total mass of the polishing liquid. More preferred is 0.5% by mass or more. The upper limit of the content of alcohol having 4 or more carbon atoms is preferably 10% by mass or less, more preferably 5% by mass or less, and more preferably 3% by mass or less based on the total mass of the polishing liquid from the viewpoint of further improving the polishing selectivity. Is more preferable, and 2% by mass or less is particularly preferable. In addition, when using a some compound as C4 or more alcohol, it is preferable that the sum total of content of each compound satisfy | fills the said range. The content of the alcohol having 4 or more carbon atoms depends on the manufacturing method (type and filming conditions) of the insulating material from the viewpoint of further improving the polishing selectivity and flatness of the insulating material with respect to silicon nitride (stopper). It is preferable to adjust appropriately.

[Other additives]
The polishing liquid according to this embodiment may further contain other additives in addition to the first additive, the second additive, and the third additive for the purpose of adjusting the polishing characteristics. . Examples of other additives include carboxylic acid, amino acid, water-soluble polymer, oxidizing agent (for example, hydrogen peroxide), alcohol admixture (for example, ethanol, diethyl ether, propylene glycol, propylpropylene glycol) and the like. These can be used individually by 1 type or in combination of 2 or more types.

  When other additives are used, the content is 0.0001% by mass or more and 10% by mass based on the total mass of the polishing liquid from the viewpoint of obtaining the additive effect while suppressing sedimentation of the abrasive grains. The following is preferred. In addition, when using a some compound as these additives, it is preferable that the sum total of content of each compound satisfy | fills the said range.

  Carboxylic acid has the effect of stabilizing the pH and further improving the polishing rate of the insulating material. Examples of the carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, and lactic acid.

  An amino acid has an effect of improving the dispersibility of abrasive grains containing a hydroxide of a tetravalent metal element and further improving the polishing rate of the insulating material. Amino acids include arginine, lysine, aspartic acid, glutamic acid, asparagine, glutamine, histidine, proline, tyrosine, tryptophan, serine, threonine, glycine, alanine, β-alanine, methionine, cysteine, phenylalanine, leucine, valine, isoleucine, etc. Can be mentioned.

  The water-soluble polymer has flatness, in-plane uniformity, polishing selectivity of silicon oxide with respect to silicon nitride (silicon oxide polishing rate / silicon nitride polishing rate), polishing selectivity of silicon oxide with respect to polysilicon (of silicon oxide) This has the effect of adjusting polishing characteristics such as (polishing rate / polysilicon polishing rate). Here, the “water-soluble polymer” is defined as a polymer that dissolves 0.1 g or more in 100 g of water. The polymer corresponding to the first additive or the second additive is not included in the “water-soluble polymer”.

  The water-soluble polymer is not particularly limited, and is an acrylic polymer such as polyacrylamide and polydimethylacrylamide; polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan, dextrin, cyclodextrin, and pullulan; polyvinyl alcohol Vinyl polymers such as polyvinylpyrrolidone and polyacrolein; glycerin polymers such as polyglycerol and polyglycerol derivatives; polyethylene glycol and the like. A water-soluble polymer can be used individually by 1 type or in combination of 2 or more types.

  When the water-soluble polymer is used, the lower limit of the content of the water-soluble polymer is 0 on the basis of the total mass of the polishing liquid from the viewpoint of obtaining the effect of adding the water-soluble polymer while suppressing sedimentation of the abrasive grains. 0.0001 mass% or more is preferable, 0.001 mass% or more is more preferable, and 0.01 mass% or more is still more preferable. The upper limit of the content of the water-soluble polymer is preferably 10% by mass or less, preferably 5% by mass based on the total mass of the polishing liquid, from the viewpoint of obtaining the effect of adding the water-soluble polymer while suppressing sedimentation of the abrasive grains. The following is more preferable, 1% by mass or less is further preferable, and 0.5% by mass or less is particularly preferable. When using a some compound as water-soluble polymer, it is preferable that the sum total of content of each compound satisfy | fills the said range.

(Liquid medium)
The liquid medium in the polishing liquid according to this embodiment is not particularly limited, but water such as deionized water or ultrapure water is preferable. The content of the liquid medium may be the remainder of the polishing liquid excluding the content of other components and is not particularly limited.

(Polishing liquid characteristics)
The pH (25 ° C.) of the polishing liquid according to this embodiment is preferably 2.0 or more and 7.0 or less from the viewpoint of further excellent storage stability of the polishing liquid and polishing suppression effect of the stopper material. The pH of the polishing liquid mainly affects the polishing rate. The lower limit of the pH is more preferably 2.5 or more, further preferably 3.0 or more, particularly preferably 3.5 or more, and extremely preferably 4.0 or more from the viewpoint of further improving the polishing rate of the insulating material. The upper limit of the pH is more preferably 6.5 or less, further preferably 6.0 or less, particularly preferably 5.7 or less, and extremely preferably 5.5 or less, from the viewpoint of further improving the polishing suppression effect of the stopper material. preferable.

  The pH of the polishing liquid can be adjusted with an acid component such as an inorganic acid or an organic acid; an alkali component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH), or imidazole. A buffer may be added to stabilize the pH. Moreover, you may add a buffer as a buffer (liquid containing a buffer). Examples of such a buffer include acetate buffer and phthalate buffer.

  The pH of the polishing liquid according to this embodiment can be measured with a pH meter (for example, model number PHL-40 manufactured by Electrochemical Instrument Co., Ltd.). Specifically, for example, after calibrating two pH meters using a phthalate pH buffer solution (pH 4.01) and a neutral phosphate pH buffer solution (pH 6.86) as standard buffers, The value is measured after the electrode is put into the polishing liquid and stabilized after 2 minutes or more. At this time, both the standard buffer solution and the polishing solution are set to 25 ° C.

  The polishing liquid according to the present embodiment may be stored as a one-part polishing liquid containing at least abrasive grains, a first additive, and a liquid medium. A slurry (first liquid) and an additive liquid (first liquid) 2 liquid) may be stored as a multi-liquid type (for example, two liquid type) polishing liquid set in which the constituents of the polishing liquid are divided into a slurry and an additive liquid so as to be the polishing liquid. . The slurry includes at least abrasive grains and a liquid medium, for example. The additive liquid includes at least a first additive, a second additive, and a liquid medium, for example. It is preferable that a 1st additive, a 2nd additive, another additive, and a buffering agent are contained in an additive liquid among slurry and an additive liquid. The constituents of the polishing liquid may be stored as a polishing liquid set divided into three or more liquids.

  In the polishing liquid set, slurry and additive liquid are mixed immediately before polishing or at the time of polishing to prepare a polishing liquid. Further, the one-component polishing liquid may be stored as a polishing liquid storage liquid in which the content of the liquid medium is reduced, and may be diluted with the liquid medium during polishing. The multi-liquid type polishing liquid set may be stored as a slurry storage liquid and an additive liquid storage liquid with a reduced content of the liquid medium, and may be diluted with the liquid medium during polishing.

  In the case of a one-component polishing liquid, the polishing liquid is supplied onto the polishing surface plate by directly supplying the polishing liquid; supplying the polishing liquid storage liquid and the liquid medium through separate pipes. , A method of supplying these by mixing and mixing them; a method of supplying the polishing liquid stock solution and the liquid medium after mixing them in advance.

  When storing as a multi-liquid type polishing liquid set divided into slurry and additive liquid, the polishing rate can be adjusted by arbitrarily changing the composition of these liquids. In the case of polishing using a polishing liquid set, there are the following methods for supplying the polishing liquid onto the polishing surface plate. For example, a method in which slurry and additive liquid are fed through separate pipes, and these pipes are combined, mixed and supplied; a slurry storage liquid, an additive liquid storage liquid, and a liquid medium are fed through separate pipes. , A method in which these are merged and mixed; a method in which slurry and additive liquid are mixed and supplied in advance; a method in which slurry storage liquid, storage liquid for additive liquid, and liquid medium are mixed in advance and supplied Can be used. Further, it is possible to use a method of supplying the slurry and the additive liquid in the polishing liquid set onto the polishing surface plate, respectively. In this case, the surface to be polished is polished using a polishing liquid obtained by mixing the slurry and the additive liquid on the polishing surface plate.

  The polishing liquid set according to the present embodiment may be divided into a polishing liquid containing at least the essential component and an additive liquid containing at least an optional component such as an oxidizing agent (for example, hydrogen peroxide). . In this case, polishing is performed using a mixed liquid obtained by mixing the polishing liquid and the additive liquid (the mixed liquid also corresponds to the “polishing liquid”). In addition, the polishing liquid set according to this embodiment is a polishing liquid set divided into three or more liquids, a liquid containing at least a part of the essential components, a liquid containing at least the remainder of the essential components, and an optional component. The mode may be divided into the additive solution containing at least. Each liquid constituting the polishing liquid set may be stored as a storage liquid in which the content of the liquid medium is reduced.

<Polishing method of substrate>
The substrate polishing method according to this embodiment may include a polishing step of polishing the surface to be polished of the substrate using the one-component polishing liquid, and the slurry and additive liquid in the polishing liquid set are mixed. You may provide the grinding | polishing process of grind | polishing the to-be-polished surface of a base | substrate using the obtained polishing liquid.

  The substrate polishing method according to this embodiment may be a method for polishing a substrate having an insulating material and polysilicon. For example, the one-part polishing liquid, or the slurry and additive liquid in the polishing liquid set. And a polishing step of selectively polishing the insulating material with respect to polysilicon using a polishing liquid obtained by mixing the above and the like. In this case, the base may have, for example, a member containing an insulating material and a member containing polysilicon. Note that “selectively polishing material A with respect to material B” means that the polishing rate of material A is higher than the polishing rate of material B under the same polishing conditions. More specifically, for example, the material A is polished at a polishing rate ratio of the polishing rate of the material A to the polishing rate of the material B of 14 or more.

  In addition, the substrate polishing method according to the present embodiment may be a method for polishing a substrate having an insulating material and silicon nitride. For example, the one-part polishing liquid or the slurry and additive liquid in the polishing liquid set A polishing step of selectively polishing the insulating material with respect to silicon nitride may be provided using a polishing liquid obtained by mixing the above. In this case, the base may have, for example, a member containing an insulating material and a member containing silicon nitride.

  In the polishing step, for example, the polishing liquid is supplied between the material to be polished and the polishing pad in a state where the material to be polished of the substrate having the material to be polished is pressed against the polishing pad (polishing cloth) of the polishing surface plate. The surface to be polished of the material to be polished is polished by relatively moving the substrate and the polishing surface plate. In the polishing step, for example, at least a part of the material to be polished is removed by polishing.

  Examples of the substrate to be polished include a substrate. For example, a material to be polished is formed on a substrate for manufacturing a semiconductor element (for example, a semiconductor substrate on which an STI pattern, a gate pattern, a wiring pattern, etc. are formed). A substrate is mentioned. Examples of materials to be polished include insulating materials such as silicon oxide; stopper materials such as polysilicon and silicon nitride. The material to be polished may be a single material or a plurality of materials. When a plurality of materials are exposed on the surface to be polished, they can be regarded as materials to be polished. The material to be polished may be in the form of a film, and may be a silicon oxide film, a polysilicon film, a silicon nitride film, or the like.

  A material to be polished (such as an insulating material such as silicon oxide) formed on such a substrate is polished with the polishing liquid, and an excess portion is removed to eliminate unevenness on the surface of the material to be polished, It can be a smooth surface over the entire surface of the abrasive material. The polishing liquid according to this embodiment is preferably used for polishing a surface to be polished containing silicon oxide.

  In this embodiment, an insulating material in a base body having an insulating material containing at least silicon oxide on the surface, a stopper (polishing stop layer) disposed under the insulating material, and a semiconductor substrate disposed under the stopper is polished. can do. The stopper material constituting the stopper is a material whose polishing rate is lower than that of the insulating material, and polysilicon, silicon nitride and the like are preferable. In such a base, since the polishing is stopped when the stopper is exposed, the insulating material can be prevented from being excessively polished, and thus the flatness of the insulating material after polishing can be improved.

According to the present invention, it is possible to sufficiently stop the polishing on the stopper even when either silicon nitride or polysilicon is used as the stopper material. In particular, when silicon nitride is used as the stopper material. In addition, the insulating material can be polished at a high polishing rate, and the polishing rate of silicon nitride can be sufficiently suppressed. According to the present invention, when polishing the insulating material using silicon nitride as the stopper material, when the stopper is exposed, the stopper and the insulating material embedded in the recess are prevented from being excessively polished. can do.
Furthermore, according to the present invention, these insulating materials can be highly planarized in the CMP technique for planarizing the shallow trench isolation insulating material, the premetal insulating material, the interlayer insulating material, and the like. In addition, according to the present invention, the insulating material can be polished with low polishing scratches while the insulating material is highly planarized.

  Examples of a method for producing a material to be polished by the polishing liquid according to this embodiment include a low pressure CVD method, a quasi-atmospheric pressure CVD method, a plasma CVD method, and other CVD methods; Etc.

Silicon oxide can be obtained, for example, by thermally reacting monosilane (SiH ₄ ) and oxygen (O ₂ ) using a low pressure CVD method. Silicon oxide can be obtained, for example, by thermally reacting tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) and ozone (O ₃ ) using a quasi-atmospheric pressure CVD method. As another example, silicon oxide is similarly obtained by causing plasma reaction between tetraethoxysilane and oxygen.

  Silicon oxide is obtained, for example, by applying a liquid raw material containing inorganic polysilazane, inorganic siloxane or the like on a substrate using a spin coating method and performing a thermosetting reaction in a furnace body or the like.

  Examples of the method for producing polysilicon include a low pressure CVD method in which monosilane is thermally reacted, a plasma CVD method in which monosilane is subjected to plasma reaction, and the like.

  As a method for producing silicon nitride, for example, a low pressure CVD method in which dichlorosilane and ammonia are thermally reacted, a plasma CVD method in which monosilane, ammonia and nitrogen are subjected to plasma reaction, and the like can be given. The silicon nitride obtained by the above method may contain elements other than silicon and nitrogen, such as carbon and hydrogen, in order to adjust the material.

  In order to stabilize materials such as silicon oxide, polysilicon, and silicon nitride obtained by the above method, heat treatment may be performed at a temperature of 200 to 1000 ° C. as necessary. Further, the silicon oxide obtained by the above method may contain a small amount of boron (B), phosphorus (P), carbon (C) or the like in order to improve the embedding property.

  Hereinafter, the polishing method according to this embodiment will be described by taking a polishing method of a semiconductor substrate on which an insulating material is formed as an example. In the polishing method according to the present embodiment, as a polishing apparatus, a general polishing apparatus having a holder capable of holding a substrate such as a semiconductor substrate having a surface to be polished and a polishing surface plate to which a polishing pad can be attached. Can be used. Each of the holder and the polishing surface plate is provided with a motor capable of changing the rotation speed. As a polishing apparatus, for example, a polishing apparatus: MIRRA manufactured by APPLIED MATERIALS can be used.

  As the polishing pad, a general nonwoven fabric, foam, non-foam, or the like can be used. As a material of the polishing pad, polyurethane, acrylic, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly-4-methylpentene, cellulose, cellulose ester, polyamide (for example, nylon (trade name) and Aramid), polyimide, polyimide amide, polysiloxane copolymer, oxirane compound, phenol resin, polystyrene, polycarbonate, epoxy resin and the like can be used. As the material of the polishing pad, in particular, foamed polyurethane and non-foamed polyurethane are preferable from the viewpoint of polishing speed and flatness. It is preferable that the polishing pad is grooved so that the polishing liquid accumulates.

Although there is no limitation on the polishing conditions, the rotation speed of the polishing platen is preferably 200 min ⁻¹ or less so that the semiconductor substrate does not pop out, and the polishing pressure (processing load) applied to the semiconductor substrate is such that polishing flaws occur. From the viewpoint of sufficiently suppressing, 100 kPa or less is preferable. During polishing, it is preferable to continuously supply the polishing liquid to the polishing pad with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with polishing liquid.

  The semiconductor substrate after the polishing is preferably washed well under running water to remove particles adhering to the substrate. For cleaning, dilute hydrofluoric acid or ammonia water may be used in addition to pure water, and a brush may be used in combination to increase cleaning efficiency. Further, after cleaning, it is preferable to dry the semiconductor substrate after water droplets adhering to the semiconductor substrate are removed using a spin dryer or the like.

  The polishing liquid, the polishing liquid set, and the polishing method according to this embodiment can be suitably used for forming STI. In order to form the STI, the polishing rate ratio of the insulating material (for example, silicon oxide) to the stopper material (for example, silicon nitride) is preferably 14 or more. When the polishing rate ratio is less than 14, the polishing rate of the insulating material relative to the polishing rate of the stopper material is small, and it tends to be difficult to stop polishing at a predetermined position when forming the STI. On the other hand, if the polishing rate ratio is 14 or more, the polishing can be easily stopped, which is more suitable for the formation of STI.

  The polishing liquid, the polishing liquid set, and the polishing method according to this embodiment can also be used for polishing a premetal insulating material. As the premetal insulating material, for example, phosphorus-silicate glass and boron-phosphorus-silicate glass are used in addition to silicon oxide, and silicon oxyfluoride, fluorinated amorphous carbon, and the like can also be used.

  The polishing liquid, the polishing liquid set, and the polishing method according to this embodiment can be applied to materials other than insulating materials such as silicon oxide. Examples of such materials include high dielectric constant materials such as Hf-based, Ti-based, and Ta-based oxides; semiconductor materials such as silicon, amorphous silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, and organic semiconductors; GeSbTe Inorganic conductive materials such as ITO; Polymer resins such as polyimides, polybenzoxazoles, acrylics, epoxies, and phenols.

  The polishing liquid, the polishing liquid set, and the polishing method according to the present embodiment are not only film-like objects to be polished, but also various types composed of glass, silicon, SiC, SiGe, Ge, GaN, GaP, GaAs, sapphire, plastic, or the like. It can also be applied to substrates.

  The polishing liquid, the polishing liquid set, and the polishing method according to the present embodiment are not only for manufacturing semiconductor elements, but also for image display devices such as TFTs and organic ELs; optical parts such as photomasks, lenses, prisms, optical fibers, and single crystal scintillators Optical elements such as optical switching elements and optical waveguides; light emitting elements such as solid lasers and blue laser LEDs; and magnetic storage devices such as magnetic disks and magnetic heads.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to this.

<Synthesis of hydroxides of tetravalent metal elements>
350 g of Ce (NH ₄ ) ₂ (NO ₃ ) ₆ 50% by mass aqueous solution (manufactured by Nippon Chemical Industry Co., Ltd., product name: CAN50 solution) was mixed with 7825 g of pure water to obtain a solution. Next, while stirring this solution, 750 g of an imidazole aqueous solution (10 mass% aqueous solution, 1.47 mol / L) was added dropwise at a mixing rate of 5 mL / min to obtain a precipitate containing cerium hydroxide. The synthesis of cerium hydroxide was performed at a temperature of 25 ° C. and a stirring speed of 400 min ⁻¹ . Stirring was carried out using a three-blade pitch paddle with a total blade length of 5 cm.

The obtained precipitate containing cerium hydroxide was centrifuged (4000 min ⁻¹ , 5 minutes) and then subjected to solid-liquid separation by removing the liquid phase by decantation. 10 g of particles obtained by solid-liquid separation and 990 g of water are mixed, and the particles are dispersed in water using an ultrasonic cleaner, and a cerium hydroxide slurry storage solution (particle content: 1.0 mass%) ) Was prepared.

<Measurement of average particle size>
It was 25 nm when the average particle diameter of the cerium hydroxide particle | grains in the stock solution for cerium hydroxide slurries was measured using the Beckman Coulter company make and brand name: N5. The measuring method is as follows. First, about 1 mL of a measurement sample (aqueous dispersion) containing 1.0% by mass of cerium hydroxide particles was placed in a 1 cm square cell, and the cell was placed in N5. The refractive index of the measurement sample was adjusted to 1.333, the viscosity of the measurement sample was adjusted to 0.887 mPa · s, the measurement was carried out at 25 ° C., and the value displayed as Unimodal Size Mean was read.

<Structural analysis of abrasive grains>
An appropriate amount of a cerium hydroxide slurry stock solution was collected, vacuum dried to isolate the abrasive grains, and then thoroughly washed with pure water to obtain a sample. When the obtained sample was measured by the FT-IR ATR method, a peak based on nitrate ion (NO ₃ ⁻ ) was observed in addition to a peak based on hydroxide ion (OH ⁻ ). Further, when XPS (N-XPS) measurement was performed on the sample, a peak based on NH ₄ ⁺ was not observed, and a peak based on nitrate ions was observed. From these results, it was confirmed that the abrasive grains contained in the cerium hydroxide slurry stock solution contained at least some particles having nitrate ions bonded to the cerium element. In addition, it was confirmed that the abrasive grains contained cerium hydroxide because they contained at least part of particles having hydroxide ions bonded to cerium element. From these results, it was confirmed that the hydroxide of cerium contains hydroxide ions bonded to the cerium element.

<Measurement of absorbance and light transmittance>
An appropriate amount of the cerium hydroxide slurry stock solution was collected and diluted with water so that the abrasive grain content was 0.0065% by mass (65 ppm) to obtain a measurement sample (aqueous dispersion). About 4 mL of this measurement sample was placed in a 1 cm square cell, and the cell was installed in a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. Absorbance was measured in the wavelength range of 200 to 600 nm, and the absorbance to light having a wavelength of 290 nm and the absorbance to light having a wavelength of 450 to 600 nm were measured. Absorbance with respect to light having a wavelength of 290 nm was 1.192, and absorbance with respect to light having a wavelength of 450 to 600 nm was less than 0.010.

  About 4 mL of a cerium hydroxide slurry storage solution (particle content: 1.0 mass%) is placed in a 1 cm square cell, and the cell is placed in a spectrophotometer (device name: U3310) manufactured by Hitachi, Ltd. did. Absorbance was measured in the wavelength range of 200 to 600 nm, and the absorbance with respect to light with a wavelength of 400 nm and the light transmittance with respect to light with a wavelength of 500 nm were measured. Absorbance with respect to light with a wavelength of 400 nm was 2.25, and light transmittance with respect to light with a wavelength of 500 nm was 92% / cm.

<Preparation of polishing liquid for CMP>
[Example 1]
5% by mass of polyethylene glycol [PEG # 600 manufactured by Lion Corporation, weight average molecular weight: 600], diallyldimethylammonium chloride acrylamide copolymer [PAS-J-81 manufactured by Nitto Bo Medical Co., Ltd., weight average molecular weight: 200000] 0.03 100 g of an additive liquid storage solution containing 10% by mass, 0.05% by mass of imidazole [pH adjusting agent], 0.05% by mass of acetic acid [pH adjusting agent] and 94.84% by mass of water, and for cerium hydroxide slurry By mixing 50 g of the stock solution, 845 g of water, and 5 g of 1-pentanol, 0.05% by mass of particles containing cerium hydroxide, 0.5% by mass of polyethylene glycol as the first additive, As the second additive, diallyldimethylammonium chloride acrylamide copolymer is 0.003 The amount%, and the third as an additive of 1-pentanol containing 0.5 wt% pH 6.1 CMP polishing liquid for preparing.

[Example 2]
Except for the blending amount of the third additive, in the same manner as in Example 1, 0.05% by mass of particles containing cerium hydroxide, 0.5% by mass of polyethylene glycol, and diallyldimethylammonium chloride acrylamide copolymer A polishing slurry for CMP having a pH of 6.1 containing 0.003% by mass and 1% by mass of 1-pentanol was prepared.

[Example 3]
Except for the molecular weight of the first additive and the type and blending amount of the third additive, 0.05% by mass of particles containing cerium hydroxide, polyethylene glycol [manufactured by NOF CORPORATION] PEG 4000, weight average molecular weight: 4000] 0.5% by mass, diallyldimethylammonium chloride acrylamide copolymer 0.003% by mass, and 0.1% by mass of 1-hexanol as a third additive, pH 6.1 A polishing liquid for CMP was prepared.

[Example 4]
Except for the blending amount of the third additive, the same procedure as in Example 3 was carried out, and 0.05% by mass of particles containing cerium hydroxide, 0.5% by mass of polyethylene glycol, and diallyldimethylammonium chloride acrylamide copolymer A polishing slurry for CMP having a pH of 6.1 containing 0.003% by mass and 0.5% by mass of 1-hexanol was prepared.

[Example 5]
Except for the type of the first additive, the same procedure as in Example 3 was carried out, except that 0.05% by mass of particles containing cerium hydroxide and polyoxyethylene styrenated phenyl ether as a first additive [Daiichi Kogyo Seiyaku Co., Ltd. Company-made Neugen EA-207D, weight average molecular weight: 5000] 0.5 mass%, diallyldimethylammonium chloride acrylamide copolymer 0.003% mass, 1-hexanol 0.1 mass%, pH 6.1 CMP A polishing liquid was prepared.

[Example 6]
Except the blending amount of the third additive, the same procedure as in Example 5 was carried out, and 0.05% by mass of particles containing cerium hydroxide, 0.5% by mass of polyoxyethylene styrenated phenyl ether, diallyldimethylammonium chloride. A polishing slurry for CMP having a pH of 6.0 containing 0.003% by mass of an acrylamide copolymer and 0.5% by mass of 1-hexanol was prepared.

[Example 7]
Except for the type and blending amount of the third additive, the same procedure as in Example 5 was carried out, and 0.05% by mass of particles containing cerium hydroxide, 0.5% by mass of polyoxyethylene styrenated phenyl ether, diallyldimethyl A polishing slurry for CMP having a pH of 6.1 containing 0.003% by mass of an ammonium chloride acrylamide copolymer and 0.05% by mass of 1-octanol as a third additive was prepared.

[Comparative Example 1]
50 g of cerium hydroxide slurry storage solution, 937 g of water, 5 g of 1% by mass imidazole aqueous solution and 8 g of 1% by mass acetic acid aqueous solution are mixed, and pH 4.2 containing 0.05% by mass of cerium hydroxide particles. A CMP abrasive was prepared.

[Comparative Example 2]
50 g of cerium hydroxide slurry storage solution, 937 g of water, 8 g of 1% by mass imidazole aqueous solution and 5 g of 1% by mass acetic acid aqueous solution are mixed to pH 6.0 containing 0.05% by mass of cerium hydroxide particles. A CMP abrasive was prepared.

[Comparative Example 3]
PH 6.5 containing 0.05% by mass of cerium hydroxide particles by mixing 50 g of cerium hydroxide slurry stock solution, 939 g of water, 8 g of 1% by mass imidazole aqueous solution and 3 g of 1% by mass acetic acid aqueous solution. A CMP abrasive was prepared.

[Comparative Example 4]
Except for not containing the third additive, the same procedure as in Example 1 was carried out, except that 0.05% by mass of particles containing cerium hydroxide, 0.5% by mass of polyethylene glycol, and diallyldimethylammonium chloride acrylamide copolymer. A polishing slurry for CMP having a pH of 6.1 containing 0.003% by mass was prepared.

[Comparative Example 5]
In the same manner as in Example 3 except that the third additive was not included, 0.05% by mass of particles containing cerium hydroxide, 0.5% by mass of polyethylene glycol, and diallyldimethylammonium chloride acrylamide copolymer A polishing slurry for CMP having a pH of 6.2 containing 0.003% by mass was prepared.

[Comparative Example 6]
Except for not containing the third additive, the same procedure as in Example 5 was carried out, except that 0.05% by mass of particles containing cerium hydroxide, 0.5% by mass of polyoxyethylene styrenated phenyl ether, and diallyldimethylammonium chloride. A polishing liquid for CMP having a pH of 6.1 containing 0.003% by mass of an acrylamide copolymer was prepared.

<Evaluation of polishing fluid properties>
The pH of the CMP polishing liquid was evaluated under the following conditions.
Measurement temperature: 25 ± 5 ° C
Measuring device: manufactured by Electrochemical Instrument Co., Ltd., model number PHL-40
Measurement method: After calibrating two points using a standard buffer (phthalate pH buffer, pH: 4.01 (25 ° C.); neutral phosphate pH buffer, pH 6.86 (25 ° C.)), The electrode was put into a polishing slurry for CMP, and the pH after being stabilized after 2 minutes or more was measured with the measuring device.

<CMP evaluation>
Each of the substrate having a silicon nitride film and the substrate having a silicon oxide film was polished under the following polishing conditions using the CMP polishing liquids of Examples 1 to 7 and Comparative Examples 1 to 6.

(CMP polishing conditions)
・ Polishing equipment: MIRRA (Applied Materials)
・ CMP polishing liquid flow rate: 200 mL / min ・ Substrate to be polished: wafer without pattern below ・ Polishing pad: foamed polyurethane resin having closed cells (Rohm and Haas Japan, model number IC1010)
Polishing pressure: 14.0 kPa (2.0 psi)
-Relative speed between substrate and polishing platen: 85 m / min-Polishing time: 1 minute-Cleaning: After CMP treatment, cleaning with ultrasonic water was performed and then drying with a spin dryer.

(Unpatterned wafer)
As a blanket wafer on which no pattern is formed, a silicon nitride film having a thickness of 0.2 μm is formed on a silicon substrate by a CVD method, and a silicon oxide film having a thickness of 1 μm is formed on the silicon substrate by a plasma CVD method. A substrate was used.

(Polished product evaluation)
[Blanket wafer polishing speed]
With respect to the substrate to be polished that has been polished and cleaned under the above conditions, the polishing rate of the film to be polished (silicon nitride film, silicon oxide film) (silicon nitride film polishing rate: SiNRR, silicon oxide film polishing rate: SiO ₂ RR) is as follows: Obtained from the equation. In addition, the film thickness difference of the film to be polished before and after polishing was determined using an optical interference film thickness apparatus (manufactured by Filmetrics, trade name: F80).
(Polishing rate: RR) = (Thickness difference of the film to be polished before and after polishing (nm)) / (Polishing time (min))

[Evaluation of polishing scratches]
The substrate to be polished (substrate having a silicon oxide film) polished and washed under the above conditions was immersed in an aqueous solution of 0.5% by mass of hydrogen fluoride for 15 seconds, and then washed with water for 60 seconds. Subsequently, the surface of the film to be polished was washed with a PVA brush for 1 minute while supplying water, and then dried. A defect of 0.2 μm or more on the surface of the film to be polished was detected using Complis made by APPLIED MATERIALS. Furthermore, when the surface of the film to be polished was observed using the defect detection coordinates obtained by Complus and SEM Vision made by APPLIED MATERIALS, the number of polishing scratches of 0.2 μm or more on the surface of the film to be polished was found to be Example 1. In any of -7 and Comparative Examples 1-6, it was about 0-5 (piece / wafer), and the generation | occurrence | production of the grinding | polishing damage | wound was fully suppressed.

  Tables 1 and 2 show the measurement results obtained for Examples 1 to 7 and Comparative Examples 1 to 6, respectively.

  Hereinafter, the results shown in Tables 1 and 2 will be described in detail.

  The polishing rate of the silicon nitride film of Example 1 was 18 nm / min, and the result that the polishing of silicon nitride was suppressed from the comparative example was obtained. Further, the polishing rate of the silicon oxide film was 249 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was 14, which is higher than the comparative example.

  The polishing rate of the silicon nitride film of Example 2 was 8 nm / min, and the result that the polishing of silicon nitride was suppressed from the comparative example was obtained. Further, the polishing rate of the silicon oxide film was 222 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was 28, which was higher than the comparative example.

  The polishing rate of the silicon nitride film of Example 3 was 15 nm / min, and the result that the polishing of silicon nitride was suppressed from the comparative example was obtained. Further, the polishing rate of the silicon oxide film was 252 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was 17, which was higher than that of the comparative example.

  The polishing rate of the silicon nitride film of Example 4 was 3 nm / min, and the result that the polishing of silicon nitride was suppressed from the comparative example was obtained. Further, the polishing rate of the silicon oxide film was 130 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was 43, which was higher than the comparative example.

  The polishing rate of the silicon nitride film of Example 5 was 12 nm / min, and the result that the polishing of silicon nitride was suppressed from the comparative example was obtained. Further, the polishing rate of the silicon oxide film was 351 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was 29, which was higher than the comparative example.

  The polishing rate of the silicon nitride film of Example 6 was 3 nm / min, and the result that the polishing of silicon nitride was suppressed from the comparative example was obtained. Further, the polishing rate of the silicon oxide film was 264 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was 88, which was higher than the comparative example.

  The polishing rate of the silicon nitride film of Example 7 was 5 nm / min, and the result that the polishing of silicon nitride was suppressed from the comparative example was obtained. Further, the polishing rate of the silicon oxide film was 338 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was 68, which was higher than the comparative example.

  The polishing rate of the silicon nitride film of Comparative Example 1 was 83 nm / min, the polishing rate of the silicon oxide film was 0 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was not obtained.

  The polishing rate of the silicon nitride film of Comparative Example 2 was 72 nm / min, the polishing rate of the silicon oxide film was 54 nm / min, and the polishing selectivity of the silicon oxide film with respect to the silicon nitride film was not obtained.

  The polishing rate of the silicon nitride film of Comparative Example 3 was 55 nm / min, the polishing rate of the silicon oxide film was 120 nm / min, and the polishing selectivity of the silicon oxide film to the silicon nitride film was 2.

  The polishing rate of the silicon nitride film of Comparative Example 4 was 47 nm / min, the polishing rate of the silicon oxide film was 226 nm / min, and the polishing selectivity of the silicon oxide film to the silicon nitride film was 5.

  The polishing rate of the silicon nitride film of Comparative Example 5 was 52 nm / min, the polishing rate of the silicon oxide film was 251 nm / min, and the polishing selectivity of the silicon oxide film to the silicon nitride film was 5.

  The polishing rate of the silicon nitride film of Comparative Example 6 was 48 nm / min, the polishing rate of the silicon oxide film was 340 nm / min, and the polishing selectivity of the silicon oxide film to the silicon nitride film was 7.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to grind | polish an insulating material with a high grinding | polishing rate, the grinding | polishing liquid which can fully suppress the grinding | polishing speed of a stopper material, a polishing liquid set, and the grinding | polishing method of a base | substrate can be provided. According to the present invention as described above, it is possible to provide a polishing liquid, a polishing liquid set, and a substrate polishing method that can improve the polishing selectivity of the insulating material with respect to the stopper material. Furthermore, according to the present invention, in CMP technology for flattening a shallow trench isolation insulating material, a pre-metal insulating material, an interlayer insulating material, and the like, the insulating material is reduced in polishing scratches while improving the polishing selectivity of the insulating material with respect to the stopper material. It can also be polished with.

Claims (14)

  A polishing liquid comprising a liquid medium, abrasive grains containing a hydroxide of a tetravalent metal element, a polyoxyalkylene compound, a cationic polymer, and an alcohol having 4 or more carbon atoms.   The polishing liquid according to claim 1, wherein the tetravalent metal element hydroxide is at least one selected from the group consisting of rare earth metal hydroxides and zirconium hydroxides.   The polishing liquid according to claim 1 or 2, wherein the content of the polyoxyalkylene compound is 0.02% by mass or more based on the total mass of the polishing liquid.   The polishing liquid according to any one of claims 1 to 3, wherein the cationic polymer is at least one selected from the group consisting of an allylamine polymer, a diallylamine polymer, a vinylamine polymer, and an ethyleneimine polymer.   The polishing liquid according to any one of claims 1 to 4, wherein the alcohol having 4 or more carbon atoms is a monovalent alcohol.   The polishing liquid according to claim 1, wherein the content of the alcohol having 4 or more carbon atoms is 0.01% by mass or more based on the total mass of the polishing liquid.   The polishing liquid according to claim 1, which is used for polishing a surface to be polished containing silicon oxide.   The constituents of the polishing liquid according to any one of claims 1 to 6 are stored separately in a first liquid and a second liquid, and the first liquid includes abrasive grains and a liquid medium. The polishing liquid set, wherein the second liquid includes a polyoxyalkylene compound, a cationic polymer, an alcohol having 4 or more carbon atoms, and a liquid medium.   A method for polishing a substrate, comprising a step of polishing a surface to be polished of the substrate using the polishing liquid according to claim 1.   A method for polishing a substrate, comprising a step of polishing a surface to be polished of a substrate using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 8.   A method for polishing a substrate having an insulating material and polysilicon, comprising: selectively polishing the insulating material with respect to the polysilicon using the polishing liquid according to claim 1. A method for polishing a substrate.   A method for polishing a substrate having an insulating material and polysilicon, wherein the insulating material is formed using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 8. A method for polishing a substrate comprising a step of selectively polishing polysilicon.   A method for polishing a substrate having an insulating material and silicon nitride, the method comprising selectively polishing the insulating material with respect to the silicon nitride using the polishing liquid according to any one of claims 1 to 6. A method for polishing a substrate.   A method for polishing a substrate having an insulating material and silicon nitride, wherein the insulating material is formed using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 8. A method for polishing a substrate, comprising a step of selectively polishing silicon nitride.

Images