Polishing composition

Abstract

Provided is a polishing composition containing an abrasive, permanganate, an aluminum salt, and water. In the polishing composition, a relation of a content W1 [% by weight] of the abrasive, a concentration C1 [mM] of the permanganate, and a concentration C2 [mM] of the aluminum salt satisfies at least one condition of the following conditions [A], [B], and [C]: [A] satisfying both of 500 ≤ (C1 / W1) and 0.04 ≤ (C2 / C1); [B] satisfying both of 200 ≤ (C1 / √ (W1)) and 8 ≤ C2; and [C] satisfying both of 500 ≤ (C1 / W1) and 8 ≤ C2.

Description

polishing composition

[0001] The present invention relates to a polishing composition. This application claims priority to Japanese Patent Application No. 2021-016870, filed on February 4, 2021, the entire contents of which are incorporated herein by reference.

[0002] Polishing using a polishing composition has been used on the surfaces of materials such as metals, semimetals, nonmetals, and their oxides. For example, surfaces made of compound semiconductor materials such as silicon carbide, boron carbide, tungsten carbide, silicon nitride, titanium nitride, and gallium nitride are processed by polishing (lapping) by supplying diamond abrasive grains between the surface and a polishing table. However, lapping using diamond abrasive grains is prone to defects and distortion due to the generation and persistence of scratches and dents. Therefore, polishing (polishing) using a polishing pad and a polishing composition after lapping using diamond abrasive grains, or instead of lapping, has been considered. Examples of literature disclosing this type of prior art include Patent Documents 1 and 2.

[0003] Japanese Patent Application Publication No. 2020-527612 International Publication No. 2020 / 087721

[0004] Generally, from the standpoint of manufacturing efficiency and cost-effectiveness, a polishing removal rate that is sufficiently high for practical use is desirable. For example, when polishing surfaces made of high-hardness materials such as silicon carbide, an improvement in the polishing removal rate is strongly desired. To address this issue, abrasives containing strong oxidizing agents such as permanganates have traditionally been used, but due to their high activity, they self-decompose during storage, making it difficult to achieve the desired polishing removal rate. Patent Document 1 also discloses a fluid composition containing at least one oxidizing agent and a polyvalent cation component. It is claimed that the use of such a fluid composition in a chemical mechanical polishing (CMP) process can achieve a relatively defect-free material surface while achieving an appropriate material removal rate (paragraph 0005). Patent Document 1's disclosure highlights that one of its features is that the fluid composition does not require abrasive particles (abrasive) (paragraph 0005). Although it mentions that an abrasive may be added (paragraph 0040), research has primarily focused on compositions that do not contain abrasives. However, there remains a need for an improvement in the polishing removal rate in polishing compositions containing abrasive grains, for purposes such as improving the productivity of products (substrates, etc.) obtained through polishing.

[0005] Here, the polishing removal rate can also be improved by adjusting the polishing conditions, such as increasing the load applied to the polishing surface during polishing to increase the processing pressure, or increasing the rotation speed of the polishing platen of the polishing apparatus.On the other hand, when a polishing composition containing abrasive grains is used to increase the polishing removal rate by selecting its composition, the temperature rise of the polishing pad during polishing (polishing) using the polishing composition tends to increase.If the temperature rise of the polishing pad can be suppressed in a polishing composition containing abrasive grains, it becomes possible to adopt more severe processing conditions, which is beneficial for further improving the polishing removal rate.In addition, Patent Document 2 relates to a chemical mechanical polishing solution with improved pH stability, but does not aim to achieve compatibility with multiple practical polishing performances such as polishing removal rate.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polishing composition that can achieve a good balance between a high polishing removal rate and suppression of a rise in the temperature of the polishing pad during polishing. Another related object is to provide a method for polishing an object to be polished using such a polishing composition.

[0007] According to the present specification, there is provided a polishing composition comprising abrasive grains, a permanganate, an aluminum salt, and water, wherein the relationship between the abrasive grain concentration W1 [wt %], the permanganate concentration C1 [mM], and the aluminum salt concentration C2 [mM] satisfies both of the following formulas (1) and (2): 500≦(C1 / W1) (1) 0.04≦(C2 / C1) (2)

[0008] According to the polishing composition of this composition, it is possible to favorably achieve both improvement of polishing removal rate and suppression of increase of polishing pad temperature (hereinafter also referred to as pad temperature) during polishing.In addition, in the above formulas (1) and (2), "W1" represents the numerical part when the content of abrasive grains in the polishing composition is expressed in "wt%" unit, "C1" represents the numerical part when the concentration of permanganate in the polishing composition is expressed in "mM" unit, and "C2" represents the numerical part when the concentration of aluminum salt in the polishing composition is expressed in "mM" unit, and W1, C1 and C2 are all dimensionless numbers.

[0009] In some preferred embodiments of the techniques disclosed herein (including polishing compositions, polishing methods, methods for producing polished products, etc.; the same applies hereinafter), the aluminum salt concentration C2 [mM] is 8 mM or more, for example, 8 mM or more and 1000 mM or less. By making the aluminum salt concentration in the polishing composition 8 mM or more, longer storage stability (shelf life) can be achieved.

[0010] In some embodiments, the abrasive concentration W1 is 0.005 wt % or more and less than 0.5 wt %. Within this range of abrasive concentration, a well-balanced effect of improving the polishing removal rate and suppressing an increase in pad temperature can be suitably achieved.

[0011] In some embodiments, the pH of the polishing composition is 5.0 or less. For a polishing composition having such a pH, it is particularly effective to apply the technology disclosed herein to achieve both an improvement in the polishing removal rate and suppression of an increase in pad temperature.

[0012] The polishing composition disclosed herein is used, for example, for polishing materials having a Vickers hardness of 1500 Hv or more. The effects of the technology disclosed herein can be favorably exhibited in polishing such high-hardness materials. In some embodiments, the material having a Vickers hardness of 1500 Hv or more is a non-oxide (i.e., a compound that is not an oxide). When polishing a non-oxide material to be polished, the polishing composition disclosed herein can favorably achieve both an improvement in the polishing removal rate and an effect of suppressing an increase in pad temperature.

[0013] The polishing composition disclosed herein is used, for example, for polishing silicon carbide. In polishing silicon carbide, the effects of the technology disclosed herein can be preferably exerted.

[0014] This specification further provides a method for polishing an object to be polished. The polishing method includes polishing the object to be polished using any of the polishing compositions disclosed herein. This polishing method can increase the polishing removal rate while suppressing an increase in pad temperature, even when polishing an object made of a high-hardness material. This can increase the productivity of the object (polished object, for example, a compound semiconductor substrate such as a silicon carbide substrate) obtained through polishing using the polishing method.

[0015] Furthermore, this specification provides a polishing composition comprising abrasive grains, a permanganate, an aluminum salt, and water, wherein the relationship between the abrasive grain concentration W1 [wt %], the permanganate concentration C1 [mM], and the aluminum salt concentration C2 [mM] satisfies both of the following formulas (3) and (4): 200≦(C1 / √(W1)) (3) 8≦C2 (4)

[0016] According to the polishing composition of this composition, it can suppress the rise of pad temperature, increase polishing removal speed, and improve storage stability (shelf life).In addition, in above formula (3) and (4), "W1" represents the numerical part when the content of abrasive grains in polishing composition is expressed in "wt%" unit, "C1" represents the numerical part when the concentration of permanganate in polishing composition is expressed in "mM" unit, and "C2" represents the numerical part when the concentration of aluminum salt in polishing composition is expressed in "mM" unit, and W1, C1 and C2 are all dimensionless numbers.

[0017] In some preferred embodiments of the technology disclosed herein, the relationship between the permanganate concentration C1 [mM] and the aluminum salt concentration C2 [mM] satisfies the following formula (5): 0.04≦(C2 / C1) (5) A polishing composition having such a composition can effectively suppress an increase in pad temperature. In formula (5), "C1" represents the numerical value when the permanganate concentration in the polishing composition is expressed in units of "mM", and "C2" represents the numerical value when the aluminum salt concentration in the polishing composition is expressed in units of "mM", and C1 and C2 are dimensionless numbers.

[0018] In some embodiments, the abrasive concentration W1 is 0.005 wt % or more and less than 0.5 wt %. Within this range of abrasive concentration, a well-balanced effect of improving the polishing removal rate and suppressing an increase in pad temperature can be suitably achieved.

[0019] In some embodiments, the pH of the polishing composition is 5.0 or less. For a polishing composition having such a pH, it is particularly effective to apply the technology disclosed herein to achieve both an improvement in the polishing removal rate and suppression of an increase in pad temperature.

[0020] The polishing composition disclosed herein is used, for example, for polishing materials having a Vickers hardness of 1500 Hv or more. The effects of the technology disclosed herein can be favorably exhibited in polishing such high-hardness materials. In some embodiments, the material having a Vickers hardness of 1500 Hv or more is a non-oxide (i.e., a compound that is not an oxide). When polishing a non-oxide material to be polished, the polishing composition disclosed herein can favorably achieve both an improvement in the polishing removal rate and an effect of suppressing an increase in pad temperature.

[0021] The polishing composition disclosed herein is used, for example, for polishing silicon carbide. In polishing silicon carbide, the effects of the technology disclosed herein can be preferably exerted.

[0022] This specification further provides a method for polishing an object to be polished. The polishing method includes polishing the object to be polished using any of the polishing compositions disclosed herein. This polishing method can increase the polishing removal rate while suppressing an increase in pad temperature, even when polishing an object made of a high-hardness material. This can increase the productivity of the object (polished object, for example, a compound semiconductor substrate such as a silicon carbide substrate) obtained through polishing using the polishing method.

[0023] Furthermore, this specification provides a polishing composition containing abrasive grains, a permanganate, an aluminum salt, and water, wherein the relationship between the abrasive grain concentration W1 [wt %], the permanganate concentration C1 [mM], and the aluminum salt concentration C2 [mM] satisfies both of the following formulas (6) and (7): 500≦(C1 / W1) (6) 8≦C2 (7)

[0024] According to the polishing composition of this composition, it can suppress the rise of pad temperature, increase polishing removal speed, and improve storage stability (shelf life).In addition, in above formula (6) and (7), "W1" represents the numerical part when the content of abrasive grains in polishing composition is expressed in "wt%" unit, "C1" represents the numerical part when the concentration of permanganate in polishing composition is expressed in "mM" unit, and "C2" represents the numerical part when the concentration of aluminum salt in polishing composition is expressed in "mM" unit, and W1, C1 and C2 are all dimensionless numbers.

[0025] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field.

[0026] <Polishing composition> (Abrasive grains) The polishing composition disclosed herein contains abrasive grains. A polishing composition containing abrasive grains can achieve a higher polishing removal rate by exerting a primarily mechanical polishing action due to the abrasive grains in addition to the primarily chemical polishing action due to the permanganate or aluminum salt. In addition, since the pad temperature tends to increase when the polishing composition contains abrasive grains, it is more effective to apply the technology disclosed herein to suppress the increase in pad temperature.

[0027] The material and properties of the abrasive grains are not particularly limited. For example, the abrasive grains may be inorganic particles, organic particles, or organic-inorganic composite particles. Examples include oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and iron oxide particles; nitride particles such as silicon nitride particles and boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; and carbonates such as calcium carbonate and barium carbonate. One type of abrasive grain may be used alone, or two or more types may be used in combination. Among these, oxide particles such as silica particles, alumina particles, cerium oxide particles, chromium oxide particles, zirconium oxide particles, manganese dioxide particles, and iron oxide particles are preferred because they can form a good surface. Among these, silica particles, alumina particles, zirconium oxide particles, chromium oxide particles, and iron oxide particles are more preferred, and silica particles and alumina particles are particularly preferred. In an embodiment in which silica particles or alumina particles are used as abrasive grains, the effect of suppressing an increase in pad temperature can be suitably achieved by applying the technology disclosed herein.

[0028] In this specification, the phrase "consisting essentially of X" or "consisting essentially of X" in relation to the composition of the abrasive grains means that the proportion of X in the abrasive grains (purity of X) is 90% or more by weight. The proportion of X in the abrasive grains is preferably 95% or more, more preferably 97% or more, even more preferably 98% or more, for example, 99% or more.

[0029] The average primary particle size of the abrasive grains is not particularly limited. From the viewpoint of easily achieving a desired polishing removal rate while suppressing an increase in pad temperature, the average primary particle size of the abrasive grains can be, for example, 5 nm or more, suitably 10 nm or more, preferably 20 nm or more, or even 30 nm or more. From the viewpoint of improving the polishing removal rate, in some embodiments, the average primary particle size of the abrasive grains may be 50 nm or more, 80 nm or more, 150 nm or more, 250 nm or more, or 350 nm or more. Furthermore, from the viewpoint of suppressing an increase in pad temperature, the average primary particle size of the abrasive grains may be, for example, 5 μm or less, preferably 3 μm or less, more preferably 1 μm or less, or may be 750 nm or less, or may be 500 nm or less. From the viewpoint of surface quality after polishing, in some embodiments, the average primary particle size of the abrasive grains may be 350 nm or less, 300 nm or less, 180 nm or less, 150 nm or less, 85 nm or less, or 50 nm or less.

[0030] In this specification, the average primary particle diameter is calculated from the specific surface area (BET value) measured by the BET method by the following formula: average primary particle diameter (nm) = 6000 / (true density (g / cm ３ ) × BET value (m ２ The specific surface area is the particle size (BET particle size) calculated by the formula: (1 / g / 2) / (2 / g). The specific surface area can be measured using, for example, a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300."

[0031] The average secondary particle diameter of the abrasive grains may be, for example, 10 nm or more, and from the viewpoint of easily increasing the polishing removal rate, it is preferably 50 nm or more, more preferably 100 nm or more, and may be 250 nm or more, or even 400 nm or more. From the viewpoint of ensuring a sufficient number per unit weight, the upper limit of the average secondary particle diameter of the abrasive grains is suitably set to approximately 10 μm or less. Furthermore, from the viewpoint of suppressing an increase in pad temperature, the average secondary particle diameter is preferably 5 μm or less, more preferably 3 μm or less, for example, 1 μm or less. From the viewpoint of surface quality after polishing, in some embodiments, the average secondary particle diameter of the abrasive grains may be 600 nm or less, 300 nm or less, 170 nm or less, or 100 nm or less.

[0032] The average secondary particle diameter of the abrasive grains can be measured as the volume average particle diameter (volume-based arithmetic mean diameter; Mv) for particles less than 500 nm by dynamic light scattering using, for example, a model "UPA-UT151" manufactured by Nikkiso Co., Ltd. Furthermore, for particles 500 nm or larger, the volume average particle diameter can be measured by, for example, a pore electrical resistance method using a model "Multisizer 3" manufactured by Beckman Coulter.

[0033] When alumina particles (alumina abrasive grains) are used as abrasive grains, they can be appropriately selected from various known alumina particles. Examples of such known alumina particles include α-alumina and intermediate alumina. Here, intermediate alumina is a general term for alumina particles other than α-alumina, and specific examples include γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, and χ-alumina. Fumed alumina (typically alumina fine particles produced by high-temperature calcination of alumina salts) may also be used, based on classification by production method. Furthermore, alumina called colloidal alumina or alumina sol (e.g., alumina hydrates such as boehmite) also fall within the scope of the known alumina particles. From the viewpoint of processability, α-alumina is preferred. The alumina abrasive grains disclosed herein may contain one type of such alumina particles alone or in combination of two or more types.

[0034] When alumina particles are used as abrasive grains, it is generally advantageous to have a higher proportion of alumina particles in the total abrasive grains used. For example, the proportion of alumina particles in the total abrasive grains is preferably 70% by weight or more, more preferably 90% by weight or more, even more preferably 95% by weight or more, and may be substantially 100% by weight.

[0035] The particle size of the alumina abrasive grains is not particularly limited and can be selected so as to achieve the desired polishing effect. From the viewpoint of improving the polishing removal rate, the average primary particle diameter of the alumina abrasive grains is preferably 50 nm or more, more preferably 80 nm or more, and may be 150 nm or more, 250 nm or more, 300 nm or more, or 350 nm or more. The upper limit of the average primary particle diameter of the alumina abrasive grains is not particularly limited, but from the viewpoint of suppressing an increase in the pad temperature, it is appropriate to set it to approximately 5 μm or less. From the viewpoint of surface quality after polishing, it is preferably 3 μm or less, more preferably 1 μm or less, and may be 750 nm or less, 500 nm or less, 400 nm or less, or 350 nm or less.

[0036] When using alumina particles as abrasive grains, the polishing composition disclosed herein may further contain abrasive grains made of materials other than the above-mentioned alumina (hereinafter also referred to as non-alumina abrasive grains) within the scope that does not impair the effects of the present invention.Examples of such non-alumina abrasive grains include abrasive grains that are substantially composed of any of oxide particles such as silica particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese oxide particles, zinc oxide particles, iron oxide particles, etc.; nitride particles such as silicon nitride particles, boron nitride particles, etc.; carbide particles such as silicon carbide particles, boron carbide particles, etc.; diamond particles; carbonates such as calcium carbonate, barium carbonate, etc.

[0037] The content of the non-alumina abrasive grains is suitably, for example, 30% by weight or less of the total weight of the abrasive grains contained in the polishing composition, preferably 20% by weight or less, and more preferably 10% by weight or less.

[0038] In another preferred embodiment of the technology disclosed herein, the polishing composition contains silica particles (silica abrasive particles) as abrasive particles. The silica abrasive particles can be appropriately selected from various known silica particles. Examples of such known silica particles include colloidal silica and dry process silica. Among these, colloidal silica is preferably used. Silica abrasive particles containing colloidal silica can suitably achieve good surface precision.

[0039] The shape (external shape) of the silica abrasive grains may be spherical or non-spherical. Specific examples of non-spherical silica abrasive grains include peanut-shaped (i.e., peanut shell-shaped), cocoon-shaped, confetti-shaped, and rugby ball-shaped. In the technology disclosed herein, the silica abrasive grains may be in the form of primary particles, or in the form of secondary particles in which a plurality of primary particles are aggregated. Furthermore, silica abrasive grains in the form of primary particles and silica abrasive grains in the form of secondary particles may be present together. In a preferred embodiment, at least a portion of the silica abrasive grains are contained in the polishing composition in the form of secondary particles.

[0040] As the silica abrasive grains, those having an average primary particle diameter of more than 5 nm can be preferably used. From the viewpoint of polishing efficiency, etc., the average primary particle diameter of the silica abrasive grains is preferably 15 nm or more, more preferably 20 nm or more, even more preferably 25 nm or more, and particularly preferably 30 nm or more. The upper limit of the average primary particle diameter of the silica abrasive grains is not particularly limited, but it is appropriate to set it to approximately 120 nm or less, preferably 100 nm or less, more preferably 85 nm or less. For example, from the viewpoint of achieving both higher levels of polishing efficiency and surface quality, silica abrasive grains having an average primary particle diameter of 12 nm to 80 nm are preferred, and silica abrasive grains having an average primary particle diameter of 15 nm to 75 nm are preferred.

[0041] The average secondary particle size of the silica abrasive grains is not particularly limited, but is preferably 20 nm or more, more preferably 50 nm or more, and even more preferably 70 nm or more, from the viewpoint of polishing efficiency, etc. Furthermore, from the viewpoint of obtaining a higher quality surface, the average secondary particle size of the silica abrasive grains is suitably 500 nm or less, preferably 300 nm or less, more preferably 200 nm or less, even more preferably 130 nm or less, and particularly preferably 110 nm or less (e.g., 100 nm or less).

[0042] The true specific gravity (true density) of the silica particles is preferably 1.5 or more, more preferably 1.6 or more, and even more preferably 1.7 or more. An increase in the true specific gravity of the silica particles tends to increase the physical polishing ability. The upper limit of the true specific gravity of the silica particles is not particularly limited, but is typically 2.3 or less, for example, 2.2 or less, 2.0 or less, or 1.9 or less. The true specific gravity of the silica particles can be measured by a liquid substitution method using ethanol as the substitution liquid.

[0043] The shape (outer shape) of silica particles is preferably spherical.Although not particularly limited, the average value of the long diameter / short diameter ratio of particles (average aspect ratio) is in principle 1.00 or more, and from the viewpoint of improving the polishing removal rate, it may be, for example, 1.05 or more, or 1.10 or more.In addition, the average aspect ratio of particles is suitably 3.0 or less, and may be 2.0 or less.From the viewpoint of improving the smoothness of the polished surface and reducing scratches, the average aspect ratio of particles is preferably 1.50 or less, may be 1.30 or less, or may be 1.20 or less.

[0044] The particle shape (external shape) and average aspect ratio can be determined, for example, by observation with an electron microscope. A specific procedure for determining the average aspect ratio involves, for example, using a scanning electron microscope (SEM) to extract the shapes of a predetermined number of particles (e.g., 200 particles). The smallest rectangle circumscribing each extracted particle shape is then drawn. The length of the long side (major axis value) of the rectangle drawn for each particle shape is then divided by the length of the short side (minor axis value) to calculate the major axis / minor axis ratio (aspect ratio). The average aspect ratio can be determined by arithmetically averaging the aspect ratios of the predetermined number of particles.

[0045] In the embodiment where the polishing composition contains silica abrasive grains, the polishing composition may further contain abrasive grains made of a material other than silica (hereinafter also referred to as non-silica abrasive grains).Examples of particles constituting such non-silica abrasive grains include oxide particles such as alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese oxide particles, zinc oxide particles, iron oxide particles, etc.; nitride particles such as silicon nitride particles, boron nitride particles, etc.; carbide particles such as silicon carbide particles, boron carbide particles, etc.; diamond particles; carbonates such as calcium carbonate and barium carbonate; etc. In some embodiments of the polishing composition containing silica abrasive grains and non-silica abrasive grains, the content of non-silica abrasive grains in the total weight of the abrasive grains contained in the polishing composition may be, for example, 30 wt% or less, 20 wt% or less, or 10 wt% or less.

[0046] The content of abrasive grains (e.g., silica abrasive grains, alumina abrasive grains, etc.) in the polishing composition disclosed herein is not particularly limited as long as it is a concentration that can realize a polishing composition that satisfies both the above formulas (1) and (2), both the above formulas (3) and (4), or both the above formulas (6) and (7), and can be appropriately set so as to achieve the desired effect depending on the purpose and usage of the polishing composition. The content of abrasive grains may be, for example, less than 5 wt%, less than 3 wt%, or less than 2 wt%. From the viewpoint of suppressing an increase in pad temperature, the content of abrasive grains is preferably less than 1 wt%, more preferably less than 0.5 wt%, more preferably 0.4 wt% or less, and may be 0.3 wt% or less, or may be 0.2 wt% or less. In some embodiments, the content of abrasive grains in the polishing composition may be 0.1 wt% or less or less than 0.1 wt%, 0.05 wt% or less or less than 0.05 wt%, 0.04 wt% or less or less than 0.04 wt%, or 0.03 wt% or less or less than 0.03 wt%. The lower limit of the content of abrasive grains is not particularly limited, and may be, for example, 0.000001 wt% or more (i.e., 0.01 ppm or more). From the viewpoint of improving the use effect of the abrasive grains, in some embodiments, the content of abrasive grains in the polishing composition may be 0.00001 wt% or more, 0.0001 wt% or more, 0.001 wt% or more, 0.002 wt% or more, or 0.005 wt% or more. When the polishing composition disclosed herein contains multiple types of abrasive grains, the content of abrasive grains in the polishing composition refers to the total content of the multiple types of abrasive grains.

[0047] The polishing composition disclosed herein preferably does not substantially contain diamond particles as particles.Diamond particles have high hardness, which can be a limiting factor in improving smoothness.In addition, diamond particles are generally expensive, so they are not considered to be an advantageous material in terms of cost-effectiveness, and from a practical standpoint, it is acceptable to have a low dependency on expensive materials such as diamond particles.Here, "particles substantially do not contain diamond particles" means that the proportion of diamond particles in the total particles is 1% by weight or less, more preferably 0.5% by weight or less, typically 0.1% by weight or less, and includes the case where the proportion of diamond particles is 0% by weight.In such an embodiment, the application effect of the present invention can be suitably exhibited.

[0048] (Permanganate) The polishing composition disclosed herein contains a permanganate. In polishing a material to be polished (for example, a high-hardness non-oxide material such as silicon carbide), the permanganate typically functions as an oxidizing agent, thereby exhibiting the effect of improving the polishing removal rate. As the permanganate, for example, an alkali metal permanganate such as sodium permanganate or potassium permanganate is preferred, and potassium permanganate is particularly preferred. Note that the permanganate may be present in the polishing composition in an ionic state.

[0049] In some embodiments of the polishing composition disclosed herein, the ratio of the permanganate concentration C1 [mM] to the abrasive grain content W1 [wt %], i.e., C1 / W1, is preferably 500 or greater. In other words, the relationship between C1 and W1 is linear, and as C1 / W1 increases, the contribution of chemical polishing to the contribution of mechanical polishing tends to be greater. By improving the polishing removal rate in a composition that satisfies 500≦C1 / W1, it is possible to achieve both a high polishing removal rate and suppression of pad temperature increases. In some embodiments, C1 / W1 may be 700 or greater, 1000 or greater, or even 1500 or greater, 3000 or greater, 5500 or greater, or 7500 or greater. The upper limit of C1 / W1 is not particularly limited, but from the viewpoint of storage stability of the polishing composition, it can be, for example, approximately 100,000 or less, or may be 20,000 or less, 75,000 or less, 50,000 or less, 10,000 or less, or 9,000 or less. In some embodiments, C1 / W1 may be 7,000 or less, 5,000 or less, or 3,000 or less.

[0050] In some embodiments of the polishing composition disclosed herein, the ratio of the permanganate concentration C1 [mM] to the square root of the abrasive content W1 [wt %], i.e., C1 / √(W1), is preferably 200 or greater. In other words, the relationship between C1 and W1 is nonlinear, and as C1 / √(W1) increases, the contribution of chemical polishing to the contribution of mechanical polishing tends to increase. By improving the polishing removal rate in a composition that satisfies 200≦C1 / √(W1), it is possible to achieve both a high polishing removal rate and suppression of pad temperature increases. In some embodiments, C1 / √(W1) may be 300 or greater, 750 or greater, or even 1500 or greater, 2500 or greater, 3500 or greater, or 4500 or greater. The upper limit of C1 / √(W1) is not particularly limited, but from the viewpoint of storage stability of the polishing composition, it can be, for example, approximately 12,000 or less, or may be 10,000 or less, 8,000 or less, or 6,000 or less. In some embodiments, C1 / √(W1) may be 4,500 or less, 3,500 or less, or 2,500 or less.

[0051] The concentration (content) of permanganate in any polishing composition disclosed herein is not particularly limited as long as it is a concentration that can realize a polishing composition that satisfies both the above formulas (1) and (2), both the above formulas (3) and (4), or both the above formulas (6) and (7), and can be appropriately set so as to achieve the desired effect depending on the purpose and mode of use of the polishing composition. In some embodiments, from the viewpoint of improving the polishing removal rate, it is appropriate for the concentration of permanganate to be approximately 5 mM or more (i.e., 0.005 mol / L or more). From the viewpoint of improving the polishing removal rate, the concentration of permanganate is preferably 10 mM or more, more preferably 30 mM or more, and may be 50 mM or more, 70 mM or more, or 90 mM or more. From the viewpoint of easily achieving a higher polishing removal rate, in some embodiments, the concentration of permanganate may be 120 mM or more, 140 mM or more, or 160 mM or more. In some embodiments, the concentration of permanganate in the polishing composition is suitably about 1000 mM or less, preferably 750 mM or less, more preferably 500 mM or less, and may be 400 mM or less, or may be 300 mM or less. Reducing the concentration of permanganate can be advantageous from the viewpoint of suppressing an increase in pad temperature. From this viewpoint, in some embodiments, the concentration of permanganate may be 250 mM or less, 200 mM or less, 150 mM or less, or 120 mM or less.

[0052] (Aluminum salt) The polishing composition disclosed herein contains an aluminum salt. In a composition containing an aluminum salt in addition to abrasive grains and permanganic acid, a polishing composition that satisfies the above-mentioned formulas (1) and (2) can effectively achieve both an improvement in the polishing removal rate and suppression of an increase in pad temperature. In addition, in a composition containing an aluminum salt in addition to abrasive grains and permanganic acid, a polishing composition that satisfies the above-mentioned formulas (3) and (4) or the above-mentioned formulas (6) and (7) can increase the polishing removal rate while suppressing an increase in pad temperature, and improve storage stability (shelf life).

[0053] The type of salt in the aluminum salt is not particularly limited, and may be an inorganic acid salt or an organic acid salt. Examples of inorganic acid salts include salts of hydrohalic acids such as hydrochloric acid, hydrobromic acid, and hydrofluoric acid, as well as salts of nitric acid, sulfuric acid, carbonic acid, silicic acid, boric acid, and phosphoric acid. Examples of organic acid salts include salts of carboxylic acids such as formic acid, acetic acid, propionic acid, benzoic acid, glycine acid, butyric acid, citric acid, tartaric acid, and trifluoroacetic acid; organic sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid; organic phosphonic acids such as methylphosphonic acid, benzenephosphonic acid, and toluenephosphonic acid; and organic phosphoric acids such as ethylphosphoric acid. Among these, salts of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid are preferred, and salts of hydrochloric acid, nitric acid, and sulfuric acid are more preferred.

[0054] In some embodiments of the polishing composition disclosed herein, the ratio (C2 / C1) of the aluminum salt concentration (if multiple aluminum salts are contained, their total concentration) C2 [mM] to the permanganate concentration (if multiple permanganates are contained, their total concentration) C1 [mM] is 0.04 or more. A composition that satisfies the above formula (1) and has a C2 / C1 ratio of 0.04 or more can preferably achieve both an improved polishing removal rate and suppressed increases in pad temperature. While not wishing to be bound by theory, the reason why the above effects are achieved by satisfying the relationship between formulas (1) and (2) is thought to be, for example, as follows. That is, the permanganate contained in the polishing composition can contribute to improving the polishing removal rate by oxidizing and embrittling the surface of the material to be polished (especially high-hardness non-oxide materials such as silicon carbide). However, this oxidation can cause an increase in the pH of the polishing composition supplied to the material to be polished. Therefore, when the pH of the polishing composition supplied to the material to be polished rises from the initial pH (i.e., the pH at the beginning of supply to the material to be polished) during polishing of the material to be polished and falls outside the appropriate pH range, the chemical polishing performance of the polishing composition on the material to be polished will be reduced.When the chemical polishing performance of the polishing composition decreases, the polishing removal rate will decrease, and the contribution of mechanical polishing performance will become relatively greater, which is thought to make the pad temperature more likely to rise.However, the above considerations do not limit the scope of the present invention.

[0055] From the viewpoint of achieving a higher level of both improvement in the polishing removal rate and suppression of an increase in pad temperature, in some embodiments, C2 / C1 is preferably 0.05 or more, more preferably 0.06 or more, and may be 0.07 or more, 0.08 or more, or 0.10 or more. The upper limit of C2 / C1 is not particularly limited, but is suitably approximately 200 or less, may be 100 or less, 75 or less, or 50 or less. In some preferred embodiments, C2 / C1 may be 20 or less, 10 or less, 5 or less, 1 or less, 0.6 or less, 0.5 or less, 0.3 or less, or 0.2 or less.

[0056] The concentration (content) of the aluminum salt in the polishing composition is not particularly limited as long as it is a concentration that can realize a polishing composition that satisfies both the above formulas (1) and (2), both the above formulas (3) and (4), or both the above formulas (6) and (7), and can be appropriately set so as to achieve the desired effect according to the purpose and mode of use of the polishing composition.The concentration of the aluminum salt may be, for example, approximately 1000 mM or less, may be 500 mM or less, or may be 300 mM or less.In some embodiments, the concentration of the aluminum salt is suitably 200 mM or less, preferably 100 mM or less, more preferably 50 mM or less, may be 30 mM or less, may be 20 mM or less, or may be 10 mM or less.The lower limit of the concentration of the aluminum salt may be, for example, 0.1 mM or more, and from the viewpoint of properly exerting the effect of use of the aluminum salt, it is advantageous to set it to 1 mM or more, and from the viewpoint of storage stability, it is preferably 5 mM or more, more preferably 7 mM or more (for example, 8 mM or more). The technology disclosed herein can also be preferably practiced in an embodiment in which the concentration of the aluminum salt in the polishing composition is 10 mM or more, 20 mM or more, or 30 mM or more, for example.

[0057] The relationship between the concentration of the aluminum salt and the content of the abrasive grains is not particularly limited as long as it is a concentration that can realize a polishing composition that satisfies both the above formulas (1) and (2), both the above formulas (3) and (4), or both the above formulas (6) and (7), and can be appropriately set according to the purpose of use and the mode of use so as to achieve the desired effect. The ratio of the aluminum salt concentration C2 [mM] to the abrasive grain content W1 [wt%], i.e., C2 / W1, can be, for example, 5 or more, preferably 10 or more, more preferably 30 or more, and may be 50 or more, or may be 80 or more. In some embodiments, C2 / W1 may be 150 or more, 300 or more, 500 or more, or 800 or more. The upper limit of C2 / W1 is not particularly limited, but from the viewpoint of the storage stability of the polishing composition, it can be, for example, approximately 10,000 or less, or may be 5,000 or less, or may be 2,500 or less. In some embodiments, C2 / W1 may be equal to or less than 1000, equal to or less than 800, or equal to or less than 600. In the above "C2 / W1," "C2" represents the numerical value when the concentration of aluminum salt in the polishing composition is expressed in units of "mM," and "W1" represents the numerical value when the content of abrasive grains in the polishing composition is expressed in units of "wt %," and both C2 and W1 are dimensionless numbers.

[0058] (Alkaline Earth Metal Salt) The polishing composition disclosed herein may contain, as an optional component, at least one metal salt A selected from alkaline earth metal salts. EMS Metal salt A EMS As the metal salt A, one kind of alkaline earth metal salt may be used alone, or two or more kinds of alkaline earth metal salts may be used in combination. EMS The use of the metal salt in combination with the above can better suppress the rise in pad temperature. EMS It is preferable that the alloy contains one or more of Mg, Ca, Sr, and Ba as an element belonging to alkaline earth metals. Of these, either Ca or Sr is preferable, and Ca is more preferable.

[0059] Metal salt A EMSThe type of salt in is not particularly limited, and may be an inorganic acid salt or an organic acid salt. Examples of inorganic acid salts include salts of hydrohalic acids such as hydrochloric acid, hydrobromic acid, and hydrofluoric acid, and salts of nitric acid, sulfuric acid, carbonic acid, silicic acid, boric acid, and phosphoric acid. Examples of organic acid salts include salts of carboxylic acids such as formic acid, acetic acid, propionic acid, benzoic acid, glycine acid, butyric acid, citric acid, tartaric acid, and trifluoroacetic acid; organic sulfonic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid; organic phosphonic acids such as methylphosphonic acid, benzenephosphonic acid, and toluenephosphonic acid; and organic phosphoric acids such as ethylphosphoric acid. Among these, salts of hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid are preferred, and salts of hydrochloric acid and nitric acid are more preferred. The technology disclosed herein can be applied to, for example, a metal salt A EMS The method can be preferably carried out in an embodiment in which a nitrate or chloride of an alkaline earth metal is used as the catalyst.

[0060] Metal salt A EMS Specific examples of alkaline earth metal salts that can be selected from include chlorides such as magnesium chloride, calcium chloride, strontium chloride, and barium chloride; bromides such as magnesium bromide; fluorides such as magnesium fluoride, calcium fluoride, strontium fluoride, and barium fluoride; nitrates such as magnesium nitrate, calcium nitrate, strontium nitrate, and barium nitrate; sulfates such as magnesium sulfate, calcium sulfate, strontium sulfate, and barium sulfate; carbonates such as magnesium carbonate, calcium carbonate, strontium carbonate, and barium carbonate; carboxylates such as calcium acetate, strontium acetate, calcium benzoate, and calcium citrate;

[0061] Metal salt A EMS is preferably a water-soluble salt. EMS By using the metal salt A contained in the polishing composition, a good surface with few defects such as scratches can be efficiently formed. EMS is preferably a compound that is not oxidized by the permanganate contained in the composition. EMS By appropriately selecting EMSThe permanganate and the metal salt A can prevent the permanganate from being deactivated due to oxidation of the metal salt A by the permanganate, and can suppress deterioration of the performance of the polishing composition over time (for example, a decrease in the polishing removal rate). EMS An example of a preferred combination is a combination of potassium permanganate and calcium nitrate.

[0062] Metal salt A EMS In some embodiments, the aluminum salt and the metal salt A EMS The anion species of the aluminum salt and the metal salt A may be the same. EMS The common anion species of the metal salt A may be, for example, nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, etc. EMS In some embodiments, the aluminum salt and the metal salt A EMS may have different anion species.

[0063] Metal salt A EMS In the polishing composition comprising the metal salt A EMS The concentration (content) of metal salt A is not particularly limited and can be appropriately set depending on the purpose and mode of use of the polishing composition so as to achieve the desired effect. EMS The concentration of metal salt A may be, for example, about 1000 mM or less, 500 mM or less, or 300 mM or less. In some embodiments, from the viewpoint of effectively achieving both an improvement in the polishing removal rate and suppression of an increase in pad temperature when used in combination with an aluminum salt, metal salt A may be used. EMS The concentration of metal salt A is suitably 200 mM or less, preferably 100 mM or less, more preferably 50 mM or less, and may be 30 mM or less, 20 mM or less, or 10 mM or less. EMS The lower limit of the concentration of metal salt A may be, for example, 0.1 mM or more. EMS From the viewpoint of properly exerting the effect of use of the metal salt A in the polishing composition, the concentration is preferably 0.5 mM or more, more preferably 1 mM or more, and may be 2.5 mM or more, or may be 5 mM or more. EMSThe concentration of the compound may be preferably 0.5 mM to 100 mM or 1 mM to 50 mM.

[0064] Although not particularly limited, metal salt A EMS From the viewpoint of making it easier to properly exhibit the effect of using metal salt A in the polishing composition, EMS Concentration of metal salts A EMS The ratio (C3 / C1) of the concentration C3 [mM] of permanganate (when a plurality of oxidizing agents are included, the total concentration thereof) to the concentration C1 [mM] of permanganate (when a plurality of oxidizing agents are included, the total concentration thereof) is preferably 0.001 or more, more preferably 0.005 or more, and may be 0.01 or more, or 0.02 or more. In some embodiments, C3 / C1 may be, for example, 0.03 or more, 0.05 or more, or 0.07 or more. The upper limit of C3 / C1 is not particularly limited, but is suitably approximately 100 or less, and may be 50 or less, 10 or less, or 5 or less. In some preferred embodiments, C3 / C1 may be 1 or less, 0.5 or less, 0.3 or less, or 0.1 or less. Such metal salt A EMS and permanganate (C3 / C1), EMS The effect of further containing the compound can be preferably exhibited.

[0065] Metal salt A EMS The relationship between the concentration C3 [mM] of the aluminum salt and the concentration C2 [mM] of the aluminum salt is not particularly limited and can be set so that the combined effect of these two salts is appropriately exhibited. For example, C3 / C2 may be in the range of 0.001 to 1000. From the viewpoint of favorably achieving both an improvement in the polishing removal rate and suppression of an increase in pad temperature, in some embodiments, C3 / C2 is suitably approximately 0.01 or more, and preferably 0.05 or more (e.g., 0.1 or more). Furthermore, C3 / C2 is suitably approximately 100 or less, preferably 50 or less, and more preferably 25 or less (e.g., 10 or less).

[0066] Metal salt A EMSThe relationship between the concentration of metal salt A and the content of abrasive grains is not particularly limited and can be appropriately set so as to achieve the desired effect depending on the purpose and mode of use. EMS The ratio of the concentration C3 [mM] of aluminum salt to metal salt A, i.e., C3 / W1, can be, for example, 5 or more, preferably 10 or more, more preferably 30 or more, and may be 50 or more, or may be 80 or more. When C3 / W1 is larger, the contribution of chemical polishing to the contribution of mechanical polishing tends to be larger. In such a composition, EMS The combined use of these can favorably exert the effect of suppressing an increase in pad temperature. In some embodiments, C3 / W1 may be 100 or more, 150 or more, 200 or more, 300 or more, or 500 or more. The upper limit of C3 / W1 is not particularly limited, but from the viewpoint of the storage stability of the polishing composition, it can be, for example, about 5000 or less, 2500 or less, or 1000 or less. In some embodiments, C3 / W1 may be 900 or less, 700 or less, or 500 or less. Note that "C3" in the above "C3 / W1" refers to the ratio of metal salt A in the polishing composition. EMS It represents the numerical value when the concentration is expressed in units of "mM". Therefore, C3 is a dimensionless number.

[0067] (Water) The polishing composition disclosed herein contains water. Ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, etc. can be preferably used as water. The polishing composition disclosed herein may further contain an organic solvent (lower alcohol, lower ketone, etc.) that can be uniformly mixed with water, as needed. Generally, it is appropriate that 90% by volume or more of the solvent contained in the polishing composition is water, preferably 95% by volume or more, and more preferably 99 to 100% by volume.

[0068] (Acid) The polishing composition may contain an acid as needed for purposes such as adjusting the pH or improving the polishing removal rate. Both inorganic and organic acids can be used as the acid. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, and carbonic acid. Examples of organic acids include aliphatic carboxylic acids such as formic acid, acetic acid, and propionic acid, aromatic carboxylic acids such as benzoic acid and phthalic acid, citric acid, oxalic acid, tartaric acid, malic acid, maleic acid, fumaric acid, succinic acid, organic sulfonic acids, and organic phosphonic acids. These acids can be used alone or in combination of two or more. When an acid is used, the amount used is not particularly limited and can be determined according to the purpose of use (e.g., pH adjustment). Alternatively, some embodiments of the polishing composition disclosed herein may be substantially acid-free.

[0069] (Basic Compound) The polishing composition may contain a basic compound as needed for purposes such as adjusting the pH or improving the polishing removal rate. Here, the term "basic compound" refers to a compound that, when added to a polishing composition, increases the pH of the composition. Examples of basic compounds include alkali metal hydroxides such as potassium hydroxide and sodium hydroxide; carbonates and bicarbonates such as ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, and sodium carbonate; ammonia; quaternary ammonium compounds, such as quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide; and other compounds such as amines, phosphates, hydrogen phosphates, and organic acid salts. The basic compound may be used alone or in combination with two or more. When a basic compound is used, its amount is not particularly limited and can be adjusted depending on the purpose of use (e.g., pH adjustment). Alternatively, some embodiments of the polishing composition disclosed herein may be substantially free of a basic compound.

[0070] (Other Components) The polishing composition disclosed herein may further contain, as needed, known additives that can be used in polishing compositions (for example, polishing compositions used for polishing high-hardness materials such as silicon carbide), such as chelating agents, thickeners, dispersants, surface protective agents, wetting agents, surfactants, rust inhibitors, preservatives, and antifungal agents, within the scope that does not impair the effects of the present invention.The content of the above-mentioned additives can be appropriately set according to the purpose of addition, and since they do not characterize the present invention, detailed explanations will be omitted.

[0071] (pH) The pH of the polishing composition is suitably about 1 to 12. When the pH is in the above range, a practical polishing removal rate is likely to be achieved. In some embodiments, the pH may be 12.0 or less, 11.0 or less, 10.0 or less, 9.0 or less, less than 9.0, 8.0 or less, less than 8.0, 7.0 or less, less than 7.0, or 6.0 or less. Metal Salt A EMS In order to more easily achieve the effects of improving the polishing removal rate and suppressing the pad temperature rise by the combined use of an aluminum salt and an aluminum salt, in some embodiments, the pH of the polishing composition is preferably less than 6.0, and may be 5.0 or less, less than 5.0, 4.0 or less, or less than 4.0. The pH may be, for example, 1.0 or more, 1.5 or more, 2.0 or more, or 2.5 or more.

[0072] The method for preparing the polishing composition disclosed herein is not particularly limited. For example, the components contained in the polishing composition may be mixed using a well-known mixing device such as a blade mixer, ultrasonic disperser, or homomixer. The manner in which these components are mixed is not particularly limited. For example, all components may be mixed at once or in an appropriate order. The polishing composition disclosed herein may be a single-component type or a multi-component type, including a two-component type. For example, Part A containing some of the components of the polishing composition (e.g., components other than water) and Part B containing the remaining components may be mixed together and used to polish an object to be polished. These may be stored separately before use and mixed at the time of use to prepare a one-component polishing composition. When mixing, water for dilution or the like may be further added.

[0073] <Object to be Polished> The object to be polished with the polishing composition disclosed herein is not particularly limited. For example, the polishing composition disclosed herein can be used to polish a substrate having a surface composed of a compound semiconductor material, i.e., a compound semiconductor substrate. The constituent material of the compound semiconductor substrate is not particularly limited and may be, for example, II-VI group compound semiconductors such as cadmium telluride, zinc selenide, cadmium sulfide, cadmium mercury telluride, or zinc cadmium telluride; III-V group compound semiconductors such as gallium nitride, gallium arsenide, gallium phosphide, indium phosphide, aluminum gallium arsenide, gallium indium arsenide, indium gallium nitride arsenide, or aluminum gallium indium phosphide; or IV-IV group compound semiconductors such as silicon carbide or germanium silicide. These materials may be conductive, doped with impurities, or insulating or semi-insulating, undoped with impurities. The object to be polished may be composed of a plurality of these materials. In a preferred embodiment, the polishing composition disclosed herein can be used to polish a substrate having a surface made of a non-oxide (i.e., non-oxide) chemical semiconductor material. In polishing a substrate having a surface made of a non-oxide chemical semiconductor material, the polishing-accelerating effect of the oxidizing agent (typically permanganate) contained in the polishing composition disclosed herein is easily and favorably exhibited.

[0074] The polishing composition disclosed herein can be preferably used for polishing a surface having a Vickers hardness of, for example, 500 Hv or more. The Vickers hardness is preferably 700 Hv or more, for example, 1000 Hv or more, or 1500 Hv or more. The Vickers hardness of the material to be polished may be 1800 Hv or more, 2000 Hv or more, or 2200 Hv or more. The upper limit of the Vickers hardness of the surface of the object to be polished is not particularly limited, and may be, for example, approximately 7000 Hv or less, 5000 Hv or less, or 3000 Hv or less. In this specification, Vickers hardness can be measured based on JIS R 1610:2003. The international standard corresponding to the above JIS standard is ISO 14705:2000.

[0075] Examples of materials having a Vickers hardness of 1500 Hv or more include silicon carbide, silicon nitride, titanium nitride, and gallium nitride. The object to be polished in the technology disclosed herein may have a single crystal surface of the above material, which is mechanically and chemically stable. The surface of the object to be polished is preferably composed of either silicon carbide or gallium nitride, and more preferably silicon carbide. Silicon carbide is expected to be a compound semiconductor substrate material with low power loss and excellent heat resistance, and the practical advantage of improving productivity by improving the polishing removal rate is particularly great. The technology disclosed herein is particularly suitable for polishing the single crystal surface of silicon carbide.

[0076] <Polishing Method> The polishing composition disclosed herein can be used to polish an object to be polished, for example, in an embodiment including the following steps. That is, a polishing liquid (slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include adjusting the concentration (e.g., diluting), adjusting the pH, etc. of the polishing composition to prepare the polishing liquid. Alternatively, the polishing composition may be used as is as the polishing liquid. In the case of a multi-component polishing composition, preparing the polishing liquid may include mixing the components, diluting one or more components before mixing, or diluting the mixture after mixing. The polishing liquid is then supplied to the object to be polished, and polishing is performed using a method commonly used by those skilled in the art. For example, the polishing liquid may be placed in a conventional polishing apparatus, and the polishing liquid is supplied to the surface of the object to be polished via the polishing pad of the polishing apparatus. Typically, the polishing liquid is continuously supplied, while the polishing pad is pressed against the surface of the object to be polished, causing relative movement (e.g., rotational movement) between the two. Polishing of the object to be polished is completed through this polishing process.

[0077] In addition, the above-mentioned contents and content ratios of each component that may be contained in the polishing composition in the technology disclosed herein typically mean the contents and content ratios in the polishing composition when actually supplied to the object to be polished (i.e., at the point of use), and therefore can be read as the contents and content ratios in the polishing liquid.

[0078] This specification provides a polishing method for polishing an object to be polished (typically, a material to be polished) and a method for manufacturing a polished product using the polishing method. The polishing method is characterized by including a step of polishing the object to be polished using the polishing composition disclosed herein. A preferred embodiment of the polishing method includes a step of performing pre-polishing (pre-polishing step) and a step of performing finish polishing (finish polishing step). In a typical embodiment, the pre-polishing step is a polishing step arranged immediately before the finish polishing step. The pre-polishing step may be a single-stage polishing step or may be a multi-stage polishing step consisting of two or more stages. The finish polishing step referred to here is a step of finish polishing the object to be polished after pre-polishing, and refers to the polishing step arranged last (i.e., most downstream) among polishing steps performed using a polishing slurry containing abrasive grains. In such a polishing method including a pre-polishing step and a finish polishing step, the polishing composition disclosed herein may be used in the pre-polishing step, in the finish polishing step, or in both the pre-polishing step and the finish polishing step.

[0079] Preliminary polishing and finish polishing can be applied to both polishing using a single-sided polishing machine and polishing using a double-sided polishing machine. In a single-sided polishing machine, the object to be polished is attached to a ceramic plate with wax or held using a holder called a carrier. While supplying a polishing composition, a polishing pad is pressed against one side of the object to be polished, and the two are moved relative to each other, thereby polishing one side of the object to be polished. The movement is, for example, rotational movement. In a double-sided polishing machine, the object to be polished is held using a holder called a carrier, and while supplying a polishing composition from above, a polishing pad is pressed against the opposing side of the object to be polished, and the two are rotated relative to each other, thereby simultaneously polishing both sides of the object to be polished.

[0080] The polishing conditions are not limited to specific conditions and are appropriately set based on the type of material to be polished, the desired surface properties (specifically, smoothness), the polishing removal rate, etc. For example, the polishing composition disclosed herein can be used over a wide pressure range, for example, from 10 kPa to 150 kPa. From the viewpoint of achieving both a high polishing removal rate and suppressing an increase in pad temperature, in some embodiments, the processing pressure may be, for example, 20 kPa or more, 30 kPa or more, or 40 kPa or more, and may be 100 kPa or less, 80 kPa or less, or 60 kPa or less. The polishing composition disclosed herein can also be preferably used for polishing under processing conditions of, for example, 30 kPa or more, and can increase the productivity of the target object (polished object) obtained through such polishing. Note that the processing pressure here is synonymous with the polishing pressure.

[0081] In the above-described polishing, the rotation speed of the platen and the rotation speed of the head of the polishing apparatus are not particularly limited and can be, for example, about 10 to 200 rpm. The rotation speed may be, for example, 20 rpm or more, or 30 rpm or more. From the viewpoint of easily achieving a higher polishing removal rate, in some embodiments, the rotation speed is preferably 55 rpm or more, more preferably 70 rpm or more, and may be 85 rpm or more, 100 rpm or more, or even 115 rpm or more. Since the use of an aluminum salt in the polishing composition containing permanganate can suppress an increase in pad temperature, polishing using the polishing composition disclosed herein can be preferably carried out even at such a relatively high rotation speed, thereby increasing the productivity of the target object (polished object) obtained through such polishing. Furthermore, from the viewpoint of suppressing an increase in pad temperature and reducing the load on the polishing apparatus, in some embodiments, the rotation speed can be, for example, 180 rpm or less, or may be 160 rpm or less, or may be 140 rpm or less. The rotation speed of the surface plate and the rotation speed of the head may be approximately the same or different.

[0082] In the above polishing, the supply rate of the polishing composition to the object to be polished was 78.54 cm２ The supply rate per surface (corresponding to one side of a 4-inch wafer) can be, for example, 200 mL / min or less, or may be 150 mL / min or less, or may be 100 mL / min or less. The lower limit of the supply rate can be, for example, 5 mL / min or more, or may be 10 mL / min or more, or may be 15 mL / min or more. Reducing the supply rate of the polishing composition is preferable from the viewpoint of reducing the environmental load by reducing the amount of waste liquid and saving space in the polishing equipment. On the other hand, when the supply rate of the polishing composition is reduced, the time the polishing composition remains on the object to be polished generally becomes longer. For this reason, it can be said that the pH of the polishing composition on the object to be polished tends to increase easily. In addition, when the supply rate of the polishing composition is reduced, the amount of heat removed by the flow of the polishing composition generally tends to decrease, which is disadvantageous from the viewpoint of suppressing an increase in the pad temperature. In polishing using the polishing composition disclosed herein, the use of an aluminum salt in the polishing composition containing a permanganate can suppress an increase in the pH of the polishing composition on the object to be polished and can also suppress an increase in the pad temperature, so that the polishing can be carried out suitably even if the supply rate of the polishing composition is relatively low. ２ The method can also be preferably carried out at a supply rate of 50 mL / min or less, 35 mL / min or less, or even 25 mL / min or less.

[0083] The polishing pad used in each polishing step disclosed herein is not particularly limited. For example, any of nonwoven fabric, suede, and hard foam polyurethane types may be used. In some embodiments, nonwoven fabric polishing pads may be preferably used. In embodiments using the above polishing pad, the effect of suppressing pad temperature rise, which is an effect of the technology disclosed herein, is preferably exhibited. Note that the polishing pad used in the technology disclosed herein is a polishing pad that does not contain abrasive grains.

[0084] The object to be polished by the method disclosed herein is typically washed after polishing. This washing can be carried out using an appropriate washing liquid. The washing liquid to be used is not particularly limited, and a known or commonly used one can be appropriately selected and used.

[0085] The polishing method disclosed herein may include any other process in addition to the pre-polishing process and the finish polishing process. Examples of such processes include a mechanical polishing process or a lapping process performed before the pre-polishing process. The mechanical polishing process involves polishing the object to be polished using a liquid in which diamond abrasive grains are dispersed in a solvent. In some preferred embodiments, the dispersion does not contain an oxidizing agent. The lapping process involves pressing the surface of a polishing platen, such as a cast iron platen, against the object to be polished to polish it. Therefore, a polishing pad is not used in the lapping process. The lapping process is typically performed by supplying abrasive grains between the polishing platen and the object to be polished. The abrasive grains are typically diamond abrasive grains. The polishing method disclosed herein may also include an additional process before the pre-polishing process or between the pre-polishing process and the finish polishing process. The additional process may be, for example, a cleaning process or a polishing process.

[0086] <Method for manufacturing a polished product> The technology disclosed herein may include a method for manufacturing a polished product, which includes a polishing step using any of the polishing methods described above, and the provision of a polished product manufactured by this method. The method for manufacturing the polished product is, for example, a method for manufacturing a silicon carbide substrate. That is, the technology disclosed herein provides a method for manufacturing a polished product, which includes polishing an object having a surface made of a high-hardness material using any of the polishing methods disclosed herein, and a polished product manufactured by this method. The manufacturing method described above can efficiently provide a substrate manufactured through polishing, such as a silicon carbide substrate.

[0087] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "%" is based on weight unless otherwise specified.

[0088] Experimental Example 1 Preparation of Polishing Composition Example A1 Alumina abrasive grains, potassium permanganate as a permanganate salt, aluminum nitrate as an aluminum salt, and deionized water were mixed to prepare a polishing composition containing 0.3% alumina abrasive grains, 189.8 mM potassium permanganate (Mn equivalent), and 30.1 mM aluminum nitrate (Al equivalent) at concentrations.

[0089] (Examples A2 to A5 and Comparative Examples A1 to A2) The polishing compositions of each example were prepared in the same manner as in Example A1, except that the concentrations of alumina abrasive grains, potassium permanganate, and aluminum nitrate were changed as shown in Table 1.

[0090] Comparative Example A3 A polishing composition according to Comparative Example A3 was prepared in the same manner as in Example A3, except that aluminum nitrate was not used.

[0091] In each polishing composition of Experimental Example 1, α-alumina abrasive grains having an average primary particle size of 310 nm were used as the alumina abrasive grains. The pH of each polishing composition was adjusted to 3.0 using nitric acid.

[0092] <Polishing of Object to be Polished> A SiC wafer was pre-polished using a preliminary polishing composition containing alumina abrasive grains. This pre-polished SiC wafer was used as the object to be polished, and the polishing composition according to each example was used as a polishing liquid as is to polish the object to be polished under the following polishing conditions. [Polishing Conditions] Polishing apparatus: Fujikoshi Machinery Co., Ltd., model "RDP-500" (platen diameter 20 inches) Polishing pad: Nitta Haas "SUBA800XY" (non-woven fabric type) Processing pressure: 44.1 kPa Platen rotation speed: 120 rpm Head rotation speed: 120 rpm Polishing liquid supply rate: 20 mL / min Polishing liquid usage method: Disposable Polishing time: 15 minutes Object to be polished: 4-inch SiC wafer (conductivity type: n-type, crystal type 4H-SiC, off-angle of main surface (0001) relative to the C-axis: 4°), 1 wafer / batch Polishing liquid temperature: 23°C

[0093] <Measurement and Evaluation> (Polishing Removal Rate) Under the above polishing conditions, a SiC wafer was polished using the polishing composition of each example, and then the polishing removal rate was calculated according to the following formulas (1) and (2): (1) Polishing stock removal [cm] = difference in weight of SiC wafer before and after polishing [g] / density of SiC [g / cm ３ ](=3.21g / cm ３ ) / polished area [cm ２ ] (=78.54cm ２ (2) Polishing removal rate [nm / h] = polishing removal amount [cm] × 10 ７ / Polishing time (= 15 / 60 hours)

[0094] The polishing removal rate obtained in each example was converted into a relative value when the rate of Comparative Example A3 was set to 100, and is shown in Table 1.

[0095] (Pad Temperature) The temperature of the polishing pad during polishing under the above polishing conditions was measured. When measuring the pad temperature, a template using a suede backing material as the wafer holding portion was used. During polishing, the wafer was kept in a state where water was applied to the suede material. The pad temperature was directly measured using the value output from the pad temperature measuring device (infrared thermal radiation thermometer) installed in the polishing apparatus. Measurements were taken from 5 minutes to 15 minutes after the start of polishing, and the average temperature during that period was taken as the pad temperature during polishing with the polishing composition of each example.

[0096] The obtained results were substituted into the following formula: ΔT [°C] = (pad temperature of Comparative Example A3) - (pad temperature of each example), and the pad temperature rise suppression effect was evaluated based on this ΔT (i.e., the amount of decrease in pad temperature relative to the pad temperature of Comparative Example A3) into the following three levels, which are shown in Table 1. A larger ΔT means a higher pad temperature decrease effect. A: ΔT is greater than 0.6°C B: ΔT is greater than 0.3°C and 0.6°C or less C: ΔT is 0.3°C or less

[0097] (Storage stability) For the polishing composition prepared above, carry out the accelerated test of storing under the environment of 60 ℃, and evaluate the storage stability.Specifically, fill the polishing composition of each example into a transparent polyethylene resin container and seal it, and leave this container under the environment of 60 ℃, and record the number of days until the pH of the polishing composition in the container increases by 2 or more as storage stability.It should be noted that, in the accelerated test of storing under 60 ℃, the storage stability of 19 days corresponds to the storage stability of approximately 12 months when stored under 25 ℃ according to the conversion based on Arrhenius law.

[0098]

[0099] As shown in Table 1, the polishing compositions of Examples A1 to A5, in which the ratio (C1 / W1) of the permanganate concentration [mM] to the abrasive content W1 [wt %] was 500 or more and / or the ratio (C1 / √(W1)) of the permanganate concentration [mM] to the square root of the abrasive content W1 [wt %] was 200 or more, and the ratio (C2 / C1) of the aluminum salt concentration C2 [mM] to the permanganate concentration C1 [mM] was 0.04 or more, exhibited an improved polishing removal rate and suppressed pad temperature rise compared to the polishing composition of Comparative Example A3, which did not contain aluminum salt. On the other hand, Comparative Examples A1 and A2, which contained aluminum salt but had small C1 / W1 and / or C1 / √(W1), exhibited a significantly lower polishing removal rate than Comparative Example A3. Comparative Example A1, in which C2 / C1 was small, exhibited a smaller effect of suppressing pad temperature rise.

[0100] Furthermore, with regard to storage stability, better results (longer storage stability) were obtained in Examples A1 to A5, which had higher aluminum salt concentrations, compared to Comparative Examples A1 and A3, which contained no aluminum salt or had a low concentration of aluminum salt.

[0101] (pH during polishing) During polishing under the above polishing conditions, the polishing liquid flowing down from the outer edge of the workpiece was sampled and its pH was measured. The polishing liquid was sampled 7 minutes after the start of polishing. The results are shown in Table 2.

[0102]

[0103] As shown in Table 2, in Comparative Example A3, which did not contain aluminum salt and had a C2 / C1 of zero, it was confirmed that the pH during polishing increased significantly compared to the initial pH. In contrast, in Examples A1 to A5, in which C2 / C1 was 0.04 or more, the increase in pH during polishing relative to the initial pH was small. In Comparative Example A1, which contained aluminum salt but had a C2 / C1 of less than 0.04, there was a tendency for the increase in pH during polishing to be slightly suppressed compared to Comparative Example A3, but the effect was insufficient. In addition, the polishing composition of Comparative Example A4, in which the aluminum salt concentration of Example A5 was changed to 4 mM and C2 / C1 was 0.021, was prepared, and the pH during polishing was measured in the same manner using this polishing composition of Comparative Example A4 (initial pH 3.0). The pH during polishing was similar to that of Comparative Example A1, and it was confirmed that when C2 / C1 was less than 0.04, the effect of suppressing the increase in pH during polishing was weak.

[0104] Experimental Example 2 Preparation of Polishing Composition Example B1 Silica abrasive grains, potassium permanganate, aluminum nitrate, and deionized water were mixed to prepare a polishing composition containing 0.1% silica abrasive grains, 189.8 mM potassium permanganate (Mn equivalent), and 30.1 mM aluminum nitrate (Al equivalent).

[0105] (Examples B2 to B3 and Comparative Example B1) The polishing compositions of each example were prepared in the same manner as in Example B1, except that the concentrations of silica abrasive grains, potassium permanganate, and aluminum nitrate were changed as shown in Table 3.

[0106] Comparative Example B2 A polishing composition according to Comparative Example B2 was prepared in the same manner as in Example B1, except that aluminum nitrate was not used.

[0107] In each polishing composition of Experimental Example 2, colloidal silica having an average primary particle size of 35 nm was used as the silica abrasive grains. The pH of each polishing composition was adjusted to 3.0 using nitric acid.

[0108] <Polishing of object to be polished> A SiC wafer was pre-polished using a preliminary polishing composition containing alumina abrasive grains. The pre-polished SiC wafer was used as the object to be polished, and the polishing composition according to each example was used as a polishing liquid as is, and the above object to be polished was polished under the same polishing conditions as in Experimental Example 1.

[0109] <Measurement and Evaluation> (Polishing Removal Rate) Values ​​obtained by measurement in the same manner as in Experimental Example 1 were converted into relative values ​​when the value of Comparative Example B2 was set at 100, and are shown in Table 3.

[0110] (Pad Temperature) The values ​​obtained by measurement in the same manner as in Experimental Example 1 were substituted into the following formula: ΔT [°C] = (pad temperature of Comparative Example B2) - (pad temperature of each example), and the pad temperature rise suppression effect was evaluated based on this ΔT (i.e., the amount of decrease in pad temperature relative to the pad temperature of Comparative Example B2) into the following three levels, which are shown in Table 3. A: ΔT is greater than 0.6°C B: ΔT is greater than 0.3°C and 0.6°C or less C: ΔT is 0.3°C or less

[0111] (Storage Stability) The storage stability was measured by the same 60° C. accelerated test as in Experimental Example 1. The results are shown in Table 3.

[0112] (pH during polishing) Measurement was carried out in the same manner as in Experimental Example 1. The results are shown in Table 4.

[0113]

[0114]

[0115] As shown in Table 3, the polishing compositions of Examples B1 to B3, in which C1 / W1 was 500 or more and / or C1 / √(W1) was 200 or more and C2 / C1 was 0.04 or more, significantly improved the polishing removal rate while suppressing the rise in pad temperature compared to the polishing composition of Comparative Example B2, which did not contain an aluminum salt. On the other hand, Comparative Example B1, which contained an aluminum salt but had a small C2 / C1, exhibited a smaller effect in suppressing the rise in pad temperature. Furthermore, Examples B1 to B3, which had a high aluminum salt concentration, had longer storage stability than Comparative Examples B1 and B2, which did not contain or had a low aluminum salt concentration. Furthermore, as shown in Table 4, in Comparative Examples B1 and B2, in which C2 / C1 was zero or less than 0.04, the pH during polishing increased significantly compared to the initial pH, whereas in Examples B1 to B3, in which C2 / C1 was 0.04 or more, the increase in pH during polishing was effectively suppressed.

[0116] Experimental Example 3 Preparation of Polishing Composition Polishing compositions according to Example A3 and Comparative Example A3 of Experimental Example 1, and polishing compositions according to Example B1 and Comparative Example B2 of Experimental Example 2 were prepared.

[0117] <Polishing of object to be polished> A SiC wafer was pre-polished using a preliminary polishing composition containing alumina abrasive grains. The pre-polished SiC wafer was used as the object to be polished, and the polishing composition according to each example was used as a polishing liquid as is, and the above-mentioned object to be polished was polished under the following two types of polishing conditions. [Polishing condition 1] Polishing apparatus: Fujikoshi Machinery Co., Ltd., model "RDP-500" (platen diameter 20 inches) Polishing pad: Nitta Haas "IC-1000" (hard polyurethane type) Processing pressure: 29.4 kPa Platen rotation speed: 100 rpm Head rotation speed: 100 rpm Polishing liquid supply rate: 20 mL / min Polishing liquid usage method: disposable Polishing time: 15 minutes Polishing object: 4-inch semi-insulating SiC wafer (conductivity type: non-doped type, crystalline type 4H-SiC, off angle of main surface (0001) to the C-axis: 0°), 1 wafer / batch Polishing liquid temperature: 23°C [Polishing condition 2] Polishing apparatus: Fujikoshi Machinery Co., Ltd., model "RDP-500" (platen diameter 20 inches) Polishing pad: Nitta Haas "IC-1000" (hard polyurethane type) Processing pressure: 39.2 kPa Platen rotation speed: 120 rpm Head rotation speed: 120 rpm Polishing liquid supply rate: 20 mL / min Polishing liquid usage method: Disposable Polishing time: 15 minutes Polishing object: 4-inch semi-insulating SiC wafer (conductivity type: non-doped type, crystalline type 4H-SiC, off angle of main surface (0001) to the C-axis: 0°), 1 wafer / batch Polishing liquid temperature: 23°C

[0118] <Measurement and Evaluation> (Polishing Removal Rate) Under the above polishing conditions, a SiC wafer was polished using the polishing composition of each example, and then the polishing removal rate was calculated according to the following formulas (1) and (2): (1) Polishing stock removal [cm] = difference in weight of SiC wafer before and after polishing [g] / density of SiC [g / cm ３ ](=3.21g / cm ３ ) / polished area [cm ２ ] (=78.54cm ２ (2) Polishing removal rate [nm / h] = polishing removal amount [cm] × 10 ７ / Polishing time (= 15 / 60 hours)

[0119] The polishing removal rate obtained in Example A3 was converted into a relative value when Comparative Example A3 was set to 100, and the results are shown in Table 5. The polishing removal rate obtained in Example B1 was converted into a relative value when Comparative Example B2 was set to 100, and the results are shown in Table 6.

[0120]

[0121]

[0122] As shown in Tables 5 and 6, the polishing compositions of Examples A3 and B1 were effective in improving the polishing removal rate compared to the polishing compositions of Comparative Examples A3 and B2, which did not contain aluminum salt, regardless of the polishing conditions, even when polishing semi-insulating SiC wafers.

[0123] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims

1. A polishing composition comprising an abrasive grain, a permanganate, an aluminum salt, and water, wherein the relationship between a concentration of the abrasive grain W1 [wt %], a concentration of the permanganate C1 [mM], and a concentration of the aluminum salt C2 [mM] satisfies both of the following formulas (1) and (2): 500≦(C1 / W1) ... (1); and 0.04≦(C2 / C1) ... (2).

2. The polishing composition according to claim 1, wherein the concentration C2 [mM] of the aluminum salt is 8 mM or more.

3. The polishing composition according to claim 1 or 2, wherein the concentration W1 of the abrasive grains is 0.005% by weight or more and less than 0.5% by weight.

4. The polishing composition according to any one of claims 1 to 3, having a pH of 5.0 or less.

5. The polishing composition according to any one of claims 1 to 4, which is used for polishing a material having a Vickers hardness of 1500 Hv or more.

6. The polishing composition according to any one of claims 1 to 5, which is used for polishing silicon carbide.

7. A polishing method comprising a step of polishing an object to be polished with the polishing composition according to any one of claims 1 to 6.

8. A polishing composition comprising an abrasive grain, a permanganate, an aluminum salt, and water, wherein the relationship between the concentration of the abrasive grain W1 [wt %], the concentration of the permanganate C1 [mM], and the concentration of the aluminum salt C2 [mM] satisfies both of the following formulas (3) and (4): 200≦(C1 / √(W1)) ... (3); and 8≦C2 ... (4).

9. The polishing composition according to claim 8, wherein the relationship between the concentration C1 [mM] of the permanganate and the concentration C2 [mM] of the aluminum salt satisfies the following formula (5): 0.04≦(C2 / C1) ...(5); 10. The polishing composition according to claim 8 or 9, wherein the concentration W1 of the abrasive grains is 0.005% by weight or more and less than 0.5% by weight.

11. The polishing composition according to any one of claims 8 to 10, having a pH of 5.0 or less.

12. The polishing composition according to any one of claims 8 to 11, which is used for polishing a material having a Vickers hardness of 1500 Hv or more.

13. The polishing composition according to any one of claims 8 to 12, which is used for polishing silicon carbide.

14. A polishing method comprising a step of polishing an object to be polished with the polishing composition according to any one of claims 8 to 13.

15. A polishing composition comprising an abrasive grain, a permanganate, an aluminum salt, and water, wherein the relationship between a concentration of the abrasive grain W1 [wt %], a concentration of the permanganate C1 [mM], and a concentration of the aluminum salt C2 [mM] satisfies both of the following formulas (6) and (7): 500≦(C1 / W1) ... (6); and 8≦C2 ... (7).