JP2016225368A - Polishing liquid for sapphire, storage liquid, and polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid for sapphire capable of polishing sapphire with a fast polishing speed while suppressing generation of vibrations of a polishing device in a CMP process.SOLUTION: The polishing liquid for sapphire includes a polyoxyethylene sorbitan fatty acid ester, abrasive grains containing silica and a liquid medium. The content of the polyoxyethylene sorbitan fatty acid ester is greater than or equal to 0.005 mass% based on the total mass of the polishing liquid.SELECTED DRAWING: None

Description

  The present invention relates to a polishing liquid for sapphire used for polishing sapphire, a storage liquid for obtaining the polishing liquid, and a polishing method using these.

  Sapphire has been used mainly for LED substrates, but it is transparent, has high hardness, and is not easily damaged. It has also been used for camera cover glass and the like, and its demand is increasing year by year.

  As a manufacturing method of the sapphire substrate, first, a lump of sapphire is made by the Bernoulli method, the Czochralski method, the EFG (Edge-defined Film-fed Growth Method) method, etc., and then cut into a substrate and thinly sliced to manufacture. A method is mentioned. When slicing, since a thin wire or the like (for example, a multi-wire saw) to which diamond particles are attached is cut out, there are fine scratches on the cut surface.

  Since the LED base is manufactured by crystal growth of GaN on the sapphire base, the surface of the sapphire is required to be very smooth for its use. In addition, even when the sapphire substrate is used for a cover glass of an electronic device housing, if the surface of the sapphire has scratches or the like, the design is deteriorated and the appearance is not beautiful. It is required to be.

  CMP (Chemical Mechanical Polishing) is indispensable for removing such scratches on the sapphire surface and smoothing it. CMP is a technique for mechanically polishing with abrasive grains and a polishing pad (polishing cloth) contained in the polishing liquid while chemically modifying the surface of the workpiece easily with a polishing liquid. However, since sapphire is very stable chemically and thermally and has a high hardness, it is difficult to perform CMP, takes a long processing time, and has a high production cost.

  In order to reduce the production cost, it is desired to improve the polishing rate of sapphire in the polishing process and shorten the polishing time. The polishing rate can be increased by increasing the pressure during polishing. However, in order to shorten the processing time, if the pressure is increased during CMP and polishing is performed under a condition that places a burden on the polishing apparatus, there may be a problem that the polishing apparatus vibrates. This vibration of the polishing apparatus is called “chatter”, and if polishing is continued for a long time with chattering, there is a risk that problems such as breakage of the apparatus may occur. For this reason, it is desired to improve the polishing rate by suppressing the vibration of the polishing apparatus by improving the polishing liquid used for polishing.

  Several polishing liquids for sapphire are known, but the types are not abundant. For example, Patent Document 1 describes polishing sapphire with a polishing liquid containing a high concentration of colloidal silica. In Patent Document 2, the sapphire polishing composition contains a surfactant, a detergent, a rust inhibitor, a surface modifier, a viscosity modifier, an antibacterial agent, a dispersant, and the like as necessary. It is described that it may be.

JP 2008-44078 A Japanese Patent No. 5384037

  However, even if sapphire is polished using the polishing liquid described in Patent Document 1 or the polishing liquid composition described in Patent Document 2, vibration of the polishing apparatus cannot be suppressed, The polishing speed of sapphire is not sufficient.

  The present invention has been made in view of the above circumstances, and can suppress the generation of vibrations of the polishing apparatus in the CMP process, and can also polish a sapphire polishing liquid capable of polishing sapphire at a high polishing rate, its storage liquid, and these An object is to provide a polishing method used.

  One embodiment of the present invention includes a polyoxyethylene sorbitan fatty acid ester, abrasive grains containing silica, and a liquid medium, and the content of the polyoxyethylene sorbitan fatty acid ester is 0.005 based on the total mass of the polishing liquid. It is related with the polishing liquid for sapphire which is the mass% or more. By using such a polishing liquid, generation of vibration of the polishing apparatus in the CMP process can be suppressed, and sapphire can be polished at a high polishing rate. Furthermore, by using the polishing liquid, sapphire can be polished smoothly at a high polishing rate.

  In one embodiment of the present invention, the pH of the polishing liquid is preferably 7.0 to 10.5. In this case, generation | occurrence | production of the vibration of the grinding | polishing apparatus in a CMP process can be suppressed further, and sapphire can be grind | polished at a still faster grinding | polishing speed.

  In one embodiment of the present invention, the silica is colloidal silica, and the average particle size of the abrasive grains is preferably 20 to 160 nm. In this case, generation | occurrence | production of the vibration of the grinding | polishing apparatus in a CMP process can be suppressed further, and sapphire can be grind | polished at a still faster grinding | polishing speed.

  In one embodiment of the present invention, the content of abrasive grains is preferably 1 to 40% by mass based on the total mass of the polishing liquid. In this case, generation | occurrence | production of the vibration of the grinding | polishing apparatus in a CMP process can be suppressed further, and sapphire can be grind | polished at a still faster grinding | polishing speed.

  One aspect of the present invention relates to a storage liquid for obtaining the polishing liquid, wherein the polishing liquid is obtained by dilution with a liquid medium. According to such a storage liquid, it is possible to reduce the cost related to the storage and transportation of the polishing liquid.

  One embodiment of the present invention relates to a polishing method including a step of polishing a surface to be polished containing sapphire using the polishing liquid. According to such a polishing method, generation of vibration of the polishing apparatus in the CMP process can be suppressed, and sapphire can be polished at a high polishing rate.

  One embodiment of the present invention relates to a polishing method including a step of polishing a surface to be polished containing sapphire using a polishing liquid obtained by diluting the stock solution with a liquid medium. According to such a polishing method, generation of vibration of the polishing apparatus in the CMP process can be suppressed, and sapphire can be polished at a high polishing rate. In addition, since the costs related to the storage, transportation, storage, etc. of the polishing liquid can be suppressed, the overall production cost can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to suppress generation | occurrence | production of the vibration of the grinding | polishing apparatus in CMP process, the polishing liquid for sapphire which can polish sapphire at a high grinding | polishing speed, its storage liquid, and the grinding | polishing method using these are provided. it can.

  Hereinafter, preferred embodiments of the present invention will be described. However, the present invention is not limited to the following embodiment.

<Polishing liquid>
The polishing liquid according to the present embodiment is a sapphire polishing liquid and is used for polishing sapphire. The polishing liquid according to the present embodiment contains polyoxyethylene sorbitan fatty acid ester, abrasive grains containing silica, and a liquid medium, and the content of polyoxyethylene sorbitan fatty acid ester is 0 based on the total mass of the polishing liquid. 0.005% by mass or more.

(Polyoxyethylene sorbitan fatty acid ester)
Examples of the polyoxyethylene sorbitan fatty acid ester include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate and the like. Among these, polyoxyethylene sorbitan monolaurate is preferable from the viewpoint of further suppressing the generation of vibration of the polishing apparatus in the CMP process and polishing sapphire smoothly at a higher polishing rate. Polyoxyethylene sorbitan fatty acid ester can be used individually by 1 type or in combination of 2 or more types.

  The content of the polyoxyethylene sorbitan fatty acid ester in the polishing liquid is 0.005% by mass or more based on the total mass of the polishing liquid. When the content of the polyoxyethylene sorbitan fatty acid ester is less than 0.005% by mass, it is difficult to obtain an effect of suppressing vibration of the polishing apparatus. The lower limit of the content of the polyoxyethylene sorbitan fatty acid ester is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more from the viewpoint of further suppressing the occurrence of vibration of the polishing apparatus. The upper limit of the content of the polyoxyethylene sorbitan fatty acid ester is preferably less than 2.0% by mass from the viewpoint of suppressing the inconvenience of handling due to an increase in the viscosity of the polishing liquid in a low temperature atmosphere of less than 5 ° C., It is more preferably less than 1.0% by mass, and still more preferably less than 0.5% by mass.

  Although the polishing liquid contains polyoxyethylene sorbitan fatty acid ester in an amount of 0.005% by mass or more, there is no clear knowledge about why the effect of suppressing the vibration of the polishing apparatus in the CMP process is obtained, The present inventors presume as follows.

  The vibration of the polishing apparatus in sapphire CMP increases the friction generated at the interface between the polishing surface containing sapphire and the polishing pad, and this stress is applied to the polishing surface including sapphire (for example, the head of the polishing apparatus). This is considered to be caused by the inability to escape between the surface of the substrate to be mounted) and the surface of the polishing pad (for example, the polishing pad mounted on the surface plate of the polishing apparatus and rotating). For this reason, the lower the number of rotations of the surface plate of the polishing apparatus and the higher the pressure of the head, the easier the vibration is generated.

  Here, it is considered that the abrasive grains in the polishing liquid play a role of relaxing friction at the interface between the surface to be polished containing sapphire and the polishing pad. And a sufficient amount of polyoxyethylene sorbitan fatty acid ester is considered to have an effect of suitably supplementing the ability to relieve the friction between the polished surface containing sapphire and the polishing pad, such as abrasive grains in the polishing liquid. . About this mechanism, intervening between the abrasive grains so as to gently bond the abrasive grains, acting as a lubricant to reduce the friction between the polished surface in the presence of the abrasive grains and the polishing pad, etc. In addition, it is estimated that the effect of reducing the vibration of the polishing apparatus is exerted by the combination thereof, but further research is required for the truth.

(Abrasive grains)
The abrasive includes silica. Conventionally, silica, alumina, and ceria are well known as constituents of abrasive grains. Among them, by using silica, a polished surface containing sapphire can be polished smoothly at an excellent polishing rate. Can do. As an abrasive grain, 2 or more types of abrasive grains from which average particle diameter, a shape, a constituent material, etc. differ can be mixed and used.

  Examples of silica include colloidal silica and fumed silica. Among the silicas, colloidal silica is preferable from the viewpoint of smoothly polishing sapphire at a further excellent polishing rate. Silica can be used alone or in combination of two or more.

  The content of silica in the abrasive grains is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more, based on the total mass of the abrasive grains. The abrasive grains may be, for example, silica particles (particles made of silica).

  From the viewpoint of further improving the polishing rate of sapphire, the viewpoint of further improving the smoothness of the surface to be polished containing sapphire after polishing, and the viewpoint of further suppressing the occurrence of vibration of the polishing apparatus, 20-160 nm is preferable, 30-130 nm is more preferable, and 40-80 nm is still more preferable.

  Here, the average particle diameter means the value of D50 (median diameter of volume distribution, cumulative median value) measured with a dynamic light scattering particle size distribution analyzer. Specifically, for example, a measurement sample is prepared by diluting an appropriate amount of polishing liquid with water as necessary so that it falls within the range of the required scattered light intensity. It is a value obtained as D50 by putting it into a particle size distribution meter. Examples of the dynamic light scattering type particle size distribution meter having such a function include a light diffraction scattering type particle size distribution meter (trade name COULTER N5 type) manufactured by COULTER Electronics. The value of the average particle diameter obtained by this dynamic light scattering particle size distribution analyzer is the average primary particle diameter measured by observing with a scanning electron microscope after the polishing liquid is appropriately diluted and dried on the sample stage. It is larger than the average primary particle size and is almost twice the average primary particle size.

  The content of the abrasive grains in the polishing liquid is preferably 1% by mass or more based on the total mass of the polishing liquid from the viewpoint of further improving the polishing rate of sapphire and further suppressing the occurrence of vibration of the polishing apparatus. 2 mass% or more is more preferable, and 4 mass% or more is still more preferable. The content of the abrasive grains is preferably 40% by mass or less, more preferably less than 40% by mass based on the total mass of the polishing liquid from the viewpoint of improving storage stability due to the fact that the abrasive grains are less likely to aggregate in the polishing liquid. Preferably, it is more preferably 30% by mass or less, and particularly preferably 20% by mass or less. Since the abrasive content is a factor that directly affects the cost of the polishing liquid, the lower the abrasive content, the lower the cost.

  The vibration of the polishing apparatus in the CMP process tends to occur more easily as the average grain size of the abrasive grains is smaller and as the abrasive grain content in the polishing liquid is smaller. Although the clear knowledge about this reason is not obtained, the present inventors presume as follows. That is, the smaller the average grain size of the abrasive grains, and the less the abrasive grain content in the polishing liquid, the less the ability to relieve friction at the interface between the polished surface containing sapphire and the polishing pad. It is considered that the vibration of the apparatus tends to occur easily.

(Sub-additive)
The polishing liquid according to the present embodiment inhibits the effects of the present invention (suppressing the vibration of the polishing apparatus in the CMP process and polishing the surface to be polished containing sapphire at a high polishing rate) as necessary. As long as it is not included, it may contain secondary additives such as pH adjusters, surfactants, detergents, rust inhibitors, surface modifiers, viscosity modifiers, antibacterial agents, and dispersants.

[PH adjuster]
Examples of pH adjusters include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; organic acids such as acetic acid, oxalic acid, malic acid, malonic acid, and picolinic acid; ammonia, sodium hydroxide, potassium hydroxide, TMAH (water And alkali components such as tetramethylammonium oxide) and imidazole. The pH of the polishing liquid can be adjusted with these pH adjusters. In order to stabilize the pH, the polishing liquid may contain a buffer solution. Examples of such a buffer include acetate buffer and phthalate buffer.

(Liquid medium)
The polishing liquid according to this embodiment contains a liquid medium. The liquid medium acts as a dispersion medium for abrasive grains. Examples of the liquid medium include water. More specifically, water is preferably deionized water, ion exchange water, ultrapure water, or the like.

(PH)
The pH of the polishing liquid according to the present embodiment is preferably 7.0 to 10.5, from the viewpoint that the polishing rate of sapphire is easily improved and the storage stability of the polishing liquid, and is preferably 7.3 to 10. 2 is more preferable, 7.5-10.0 is still more preferable, and 8.0-9.8 is especially preferable. The pH is defined as the pH at a liquid temperature of 25 ° C.

  The pH of the polishing liquid can be measured with a pH meter (for example, manufactured by HORIBA, Ltd., model number: pH MATE F-50). As pH measurement values, standard buffer solution (phthalate pH buffer solution pH: 4.01 (25 ° C), neutral phosphate pH buffer solution pH: 6.86 (25 ° C), borate pH buffer solution After calibrating three points using the liquid pH: 9.18 (25 ° C.), the electrode is placed in the polishing liquid, and the value after 2 minutes or more has elapsed is adopted.

<Storage solution>
The polishing liquid according to the present embodiment can be stored as a storage liquid that is diluted with a liquid medium such as water during use. That is, the storage liquid according to the present embodiment is a storage liquid for obtaining the above-described polishing liquid, and the polishing liquid is obtained by diluting with a liquid medium (for example, diluting twice or more on a mass basis). By storing the polishing liquid as a stock solution, costs associated with storage, transportation, storage, etc. can be suppressed. The storage liquid may be diluted with a liquid medium immediately before polishing to obtain a polishing liquid, or the storage liquid and the liquid medium may be supplied on a polishing surface plate to prepare the polishing liquid on the polishing surface plate. Good.

  Since the higher the dilution rate of the stock solution is, the higher the effect of suppressing the cost related to storage, transportation, storage, etc., the lower limit of the stock solution dilution rate is preferably 2 times or more and more preferably 3 times or more on a mass basis. The upper limit of the dilution ratio of the stock solution is not particularly limited, but is preferably 10 times or less, more preferably 7 times or less, and still more preferably 5 times or less on a mass basis. When the dilution ratio is less than or equal to these upper limit values, the content of abrasive grains contained in the stock solution is prevented from becoming too high, and the stability of the stock solution during storage tends to be easily maintained. When the dilution ratio is d, the contents of the abrasive grains and polyoxyethylene sorbitan fatty acid ester in the storage liquid are d times the respective contents of the abrasive grains and polyoxyethylene sorbitan fatty acid ester in the polishing liquid. is there.

<Polishing method>
The polishing method (sapphire polishing method) according to the present embodiment includes a polishing step of polishing a surface to be polished containing sapphire using the above-described polishing liquid. The polishing step may be a step including a step of polishing a surface to be polished containing sapphire using a polishing liquid obtained by diluting the above-described storage liquid with a liquid medium.

  In the polishing method according to this embodiment, a known polishing apparatus can be widely used. For example, when polishing a substrate having a surface to be polished (sapphire substrate) containing sapphire, a polishing apparatus that can be used is connected to a holder for holding the sapphire substrate on the head, a motor whose rotation speed can be changed, and the like. A general polishing apparatus having a surface plate with a polishing pad attached thereto can be used.

Although it does not specifically limit as a polishing pad, A general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. are mentioned. The polishing conditions for the substrate are not limited, but from the viewpoint of easily preventing the substrate from popping out, the rotation speed of the surface plate is preferably 200 min ⁻¹ or less. From the viewpoint of easily suppressing the generation of scratches on the substrate surface after polishing, the polishing load is preferably 700 gf / cm ² or less.

  In the polishing method according to the present embodiment, for example, while supplying the polishing liquid between the surface to be polished and the polishing pad with a pump or the like in a state where the sapphire substrate is pressed against the polishing pad attached to the surface plate, Move the base and the surface plate relatively. By these operations, the surface to be polished containing sapphire is polished. The method for supplying the polishing liquid to the polishing apparatus is not particularly limited as long as the polishing liquid can be continuously supplied to the polishing pad during polishing. The supply amount of the polishing liquid is not limited, but it is preferable that the surface of the polishing pad is always covered with the polishing liquid. Supply the storage liquid and a liquid medium such as water between the surface to be polished and the polishing pad, and perform polishing while diluting the storage liquid on the polishing surface plate (for example, diluting it twice or more on a mass basis). Also good. Further, the supplied polishing liquid may be collected and supplied to the polishing pad again, and used after circulation.

  The substrate after the polishing is preferably washed with water, ethanol, isopropyl alcohol, or other cleaning agents, and then dried after removing water droplets adhering to the substrate using a spin dryer or the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not restrict | limited to these Examples, unless it deviates from the technical idea of this invention.

<Average particle size of abrasive grains>
The average particle diameters of the abrasive grains (silica A and silica B) used in Examples and Comparative Examples were measured with a light diffraction scattering type particle size distribution meter (trade name: COULTER N5 type) manufactured by COULTER Electronics. The average particle diameter of silica A was 68 nm, and the average particle diameter of silica B was 44 nm. In addition, as a dispersion composed of silica A and water, Cataloid SI-45P (“Cataloid” is a registered trademark, the same shall apply hereinafter; manufactured by JGC Catalysts & Chemicals Co., Ltd., average primary particle size 45 nm, colloidal silica content 40% by mass) As a dispersion composed of silica B and water, Cataloid SI-50 (manufactured by JGC Catalysts & Chemicals, Inc., average primary particle size 25 nm, colloidal silica content 48 mass%) was used.

<Example 1>
(Storage solution 1)
As a dispersion composed of silica A and water, 96 parts by mass of cataloid SI-45P, 0.4 parts by mass of polyoxyethylene sorbitan monolaurate, 3.20 parts by mass of deionized water, 1,2,4- A stock solution 1 was prepared by dissolving and mixing 0.32 parts by mass of triazole and 0.08 parts by mass of malic acid.

(Polishing liquid 1)
By mixing 1 part by mass of the stock solution 1 and 3 parts by mass of deionized water, the stock solution 1 was diluted 4 times to prepare a polishing liquid 1. The content of silica A in the polishing liquid 1 was 9.600% by mass, and the content of polyoxyethylene sorbitan monolaurate was 0.100% by mass. The “content” is the content based on the total mass of the polishing liquid (the same applies hereinafter).

<Example 2>
(Stock solution 2)
As a dispersion composed of silica A and water, 96 parts by mass of cataloid SI-45P, 0.04 parts by mass of polyoxyethylene sorbitan monolaurate, 3.56 parts by weight of deionized water, and 1,2,4- A stock solution 2 was prepared by dissolving and mixing 0.32 parts by mass of triazole and 0.08 parts by mass of malic acid.

(Polishing liquid 2)
By mixing 1 part by mass of the storage liquid 2 and 3 parts by mass of deionized water, the storage liquid 2 was diluted 4 times to prepare a polishing liquid 2. The content of silica A in the polishing liquid 2 was 9.600% by mass, and the content of polyoxyethylene sorbitan monolaurate was 0.010% by mass.

<Example 3>
(Stock solution 3)
A stock solution 3 similar to the stock solution 1 was prepared.

(Polishing liquid 3)
By mixing 1 part by mass of the stock solution 3 and 5 parts by mass of deionized water, the stock solution 3 was diluted 6 times to prepare a polishing solution 3. The content of silica A in the polishing liquid 3 was 6.400% by mass, and the content of polyoxyethylene sorbitan monolaurate was 0.067% by mass.

<Example 4>
(Stock solution 4)
As a dispersion composed of silica B and water, 80 parts by mass of Cataloid SI-50, 0.4 parts by mass of polyoxyethylene sorbitan monolaurate, 19.20 parts by mass of deionized water, 1,2,4- A stock solution 4 was prepared by dissolving and mixing 0.32 parts by mass of triazole and 0.08 parts by mass of malic acid.

(Polishing liquid 4)
By mixing 1 part by mass of the storage liquid 4 and 3 parts by mass of deionized water, the storage liquid 4 was diluted 4 times to prepare a polishing liquid 4. The content of silica B in the polishing liquid 4 was 9.600% by mass, and the content of polyoxyethylene sorbitan monolaurate was 0.100% by mass.

<Comparative Example 1>
(Storage solution X1)
As a dispersion composed of silica A and water, 96 parts by weight of cataloid SI-45P, 3.60 parts by weight of deionized water, 0.32 parts by weight of 1,2,4-triazole, and 0.08 parts by weight of malic acid The stock solution X1 was prepared by dissolving and mixing the parts.

(Polishing liquid X1)
By mixing 1 part by mass of the storage liquid X1 and 3 parts by mass of deionized water, the storage liquid X1 was diluted 4 times to prepare a polishing liquid X1. The content of silica A in the polishing liquid X1 was 9.600% by mass.

<Comparative example 2>
(Storage solution X2)
As a dispersion composed of silica A and water, 96 parts by weight of cataloid SI-45P, 0.016 parts by weight of polyoxyethylene sorbitan monolaurate, 3.584 parts by weight of deionized water, 1,2,4- A stock solution X2 was prepared by dissolving and mixing 0.32 parts by mass of triazole and 0.08 parts by mass of malic acid.

(Polishing liquid X2)
By mixing 1 part by mass of the storage liquid X2 and 3 parts by mass of deionized water, the storage liquid X2 was diluted 4 times to prepare a polishing liquid X2. The content of silica A in the polishing liquid X2 was 9.600% by mass, and the content of polyoxyethylene sorbitan monolaurate was 0.004% by mass.

<Comparative Example 3>
(Storage solution X3)
96 parts by mass of Cataloid SI-45P as a dispersion composed of silica A and water, and 0.4 parts by mass of Jurimer AC-10LP as polyacrylic acid (“Jurimer” is a registered trademark, manufactured by Nippon Pure Chemical Co., Ltd.) A stock solution X3 was prepared by dissolving and mixing 3.20 parts by mass of deionized water, 0.32 parts by mass of 1,2,4-triazole, and 0.08 parts by mass of malic acid.

(Polishing liquid X3)
By mixing 1 part by mass of the storage liquid X3 and 3 parts by mass of deionized water, the storage liquid X3 was diluted 4 times to prepare a polishing liquid X3. The content of silica A in the polishing liquid X3 was 9.600% by mass, and the content of polyacrylic acid was 0.100% by mass.

<Comparative example 4>
(Storage solution X4)
96 parts by weight of cataloid SI-45P as a dispersion composed of silica A and water, and 0.4 parts by weight of PGL X (“PGL X” is a trade name, manufactured by Daicel Corporation, 20-mer) as polyglycerin, A stock solution X4 was prepared by dissolving and mixing 3.20 parts by mass of deionized water, 0.32 parts by mass of 1,2,4-triazole, and 0.08 parts by mass of malic acid.

(Polishing liquid X4)
By mixing 1 part by mass of the storage liquid X4 and 3 parts by mass of deionized water, the storage liquid X4 was diluted 4 times to prepare a polishing liquid X4. The content of silica A in the polishing liquid X4 was 9.600% by mass, and the content of polyglycerin was 0.100% by mass.

<Comparative Example 5>
(Storage solution X5)
As a dispersion composed of silica A and water, 96 parts by mass of cataloid SI-45P, 0.072 parts by mass of γ-butyrolactone, 3.528 parts by mass of deionized water, and 0.32, 1,2,4-triazole A stock solution X5 was prepared by dissolving and mixing parts by mass and 0.08 parts by mass of malic acid.

(Polishing liquid X5)
By mixing 1 part by mass of the storage liquid X5 and 3 parts by mass of deionized water, the storage liquid X5 was diluted 4 times to prepare a polishing liquid X5. The content of silica A in the polishing liquid X5 was 9.600% by mass, and the content of γ-butyrolactone was 0.018% by mass.

<Comparative Example 6>
(Storage solution X6)
As a dispersion composed of silica A and water, 96 parts by weight of cataloid SI-45P, 1.0 part by weight of diethylene glycol, 2.60 parts by weight of deionized water, and 0.32 parts by weight of 1,2,4-triazole Then, 0.08 parts by mass of malic acid was dissolved and mixed to prepare a stock solution X6.

(Polishing liquid X6)
By mixing 1 part by mass of the storage liquid X6 and 3 parts by mass of deionized water, the storage liquid X6 was diluted 4 times to prepare a polishing liquid X6. The content of silica A in the polishing liquid X6 was 9.600% by mass, and the content of diethylene glycol was 0.250% by mass.

<Comparative Example 7>
(Storage solution X7)
As a dispersion composed of silica A and water, 96 parts by weight of cataloid SI-45P, 1.0 part by weight of 1,3-butanediol, 2.60 parts by weight of deionized water, and 1,2,4-triazole A stock solution X7 was prepared by dissolving and mixing 0.32 parts by mass and 0.08 parts by mass of malic acid.

(Polishing liquid X7)
By mixing 1 part by mass of the storage liquid X7 and 3 parts by mass of deionized water, the storage liquid X7 was diluted 4 times to prepare a polishing liquid X7. The content of silica A in the polishing liquid X7 was 9.600% by mass, and the content of 1,3-butanediol was 0.250% by mass.

<Comparative Example 8>
(Stock solution X8)
A stock solution X8 similar to the stock solution X1 was prepared.

(Polishing liquid X8)
By mixing 1 part by mass of the storage liquid X8 and 5 parts by mass of deionized water, the storage liquid X8 was diluted 6 times to prepare a polishing liquid X8. The content of silica A in the polishing liquid X8 was 6.400% by mass.

<Comparative Example 9>
(Storage solution X9)
As a dispersion composed of silica B and water, 80 parts by mass of cataloid SI-50, 19.60 parts by weight of deionized water, 0.32 parts by weight of 1,2,4-triazole, and 0.08 parts by weight of malic acid The solution X9 was dissolved and mixed to prepare a stock solution X9.

(Polishing liquid X9)
By mixing 1 part by mass of the storage liquid X9 and 3 parts by mass of deionized water, the storage liquid X9 was diluted 4 times to prepare a polishing liquid X9. The content of silica B in the polishing liquid X9 was 9.600% by mass.

<PH measurement and pH adjustment of polishing liquid>
The pH at 25 ° C. of the polishing liquids of Examples and Comparative Examples was measured using a pH meter “pH MATE F-50” manufactured by Horiba, Ltd. If the pH of the polishing liquid is 9.2 to 9.3, use it as it is, and if it is higher than 9.3, add a small amount of 20% by weight malic acid aqueous solution as the pH adjusting liquid. The pH was adjusted to 9.2 to 9.3. In the examples and comparative examples, the pH did not fall below 9.2. A 20% by mass malic acid aqueous solution was prepared by dissolving 20 parts by mass of malic acid in 80 parts by mass of deionized water at room temperature. In addition, the amount of malic acid in the polishing liquid to which the pH adjusting liquid was added was equivalent to the amount of malic acid in the polishing liquid before the pH adjusting liquid was added.

<Sapphire substrate used for CMP evaluation>
In the CMP evaluation, a plane orientation C-plane sapphire wafer having a diameter of 50.8 mm (2 inches) and a thickness of 0.43 mm was used as the sapphire substrate. The average surface roughness (Ra) before polishing was 0.2 nm. The average surface roughness (Ra) was measured using a scanning probe microscope (“SPI3800N / SPA500” manufactured by Seiko Instruments Inc.) in a measurement region of 1 micron.

<Evaluation of vibration of polishing apparatus in CMP process>
While the polishing liquids 1 to 4 and the polishing liquids X1 to X9 obtained above are dropped onto a pad attached to a surface plate, CMP is performed under the following polishing conditions (polishing conditions 1 and 2). The vibration of the device was evaluated. The polishing conditions other than the rotation speed of the polishing surface plate in the polishing conditions 2 were the same as those in the polishing conditions 1. The case where vibration did not occur was evaluated as “◯”, and the case where vibration occurred was evaluated as “x”. The evaluation results are shown in Tables 1 and 2. Vibration evaluation evaluated that the case where it was "(circle)" in the grinding conditions 1 was favorable.

(Polishing condition 1)
Polishing apparatus: RDP-500, manufactured by Fujikoshi Machinery Co., Ltd.
Polishing pad: Rohm and Haas, IC1000XY-Groove
Polishing pressure: 600 gf / cm ²
Flow rate of polishing liquid: 500 ml / min (1000 ml of polishing liquid was circulated)
Polishing time: 1 minute Sapphire substrate: 5 Polishing platen rotational speed: 40 min ⁻¹
(Polishing condition 2)
Rotation speed of polishing surface plate: 30 min ⁻¹

<Evaluation of sapphire polishing rate by CMP>
While dripping the polishing liquids 1 to 4 and the polishing liquids X1 to X9 obtained above onto a pad attached to a surface plate, a CMP process is performed under the polishing conditions 3 shown below, and the polishing rate and average surface roughness (Ra ) Was evaluated. The evaluation results are shown in Tables 1 and 2.

(Polishing condition 3)
Polishing device: FACT-200, manufactured by Nano Factor Co., Ltd.
Polishing pad: Rohm and Haas, IC1000K-Groove
Polishing pressure: 300 gf / cm ²
Flow rate of polishing liquid: 100 ml / min (125 ml of polishing liquid was circulated)
Polishing time: 30 minutes Sapphire substrate: 5 Polishing platen rotation speed: 90 min ⁻¹

(Polishing speed)
The polishing rate was determined by measuring the mass of the substrate before and after the CMP treatment to determine the mass of the polished sapphire, and using the surface area of the substrate to be polished and the density of sapphire 3.97 g / cm ³ The thickness was calculated from the relationship between the reduced film thickness and the polishing time. The polishing rate was evaluated as 1.0 μm / h or more as good.

(Average surface roughness (Ra))
Average surface roughness (Ra) was measured by the same method as described in <Sapphire substrate used for CMP evaluation>. The average surface roughness (Ra) was evaluated as good when less than 0.3 nm.

  As is clear from the results of the examples, when the polishing liquid contains 0.005% by mass or more of polyoxyethylene sorbitan fatty acid ester, generation of vibration of the polishing apparatus is suppressed in the CMP process, and the surface to be polished containing sapphire Can be polished smoothly at a high polishing rate.

  As is clear from the results of Comparative Examples 1 and 2, when the content of the polyoxyethylene sorbitan fatty acid ester is less than 0.005% by mass, the occurrence of vibration of the polishing apparatus could not be suppressed in the CMP process. As is apparent from the results of Comparative Examples 3 and 4, even when a surfactant other than polyoxyethylene sorbitan fatty acid ester was used, the occurrence of vibrations in the polishing apparatus could not be suppressed in the CMP process. As is clear from the results of Comparative Examples 5 to 7, even when an organic solvent was used instead of the polyoxyethylene sorbitan fatty acid ester, generation of vibrations in the polishing apparatus could not be suppressed in the CMP process.

  As is apparent from the results of Example 3 and Comparative Example 8, the polishing liquid was polyoxyethylene sorbitan fatty acid even when the abrasive content was 6.400% by mass, which was less than 9.600% by mass. By containing 0.005 mass% or more of ester, generation | occurrence | production of the vibration of the grinding | polishing apparatus was suppressed by CMP process, and the to-be-polished surface containing sapphire was able to be smoothly grind | polished at a high grinding | polishing speed.

  As is clear from the results of Example 4 and Comparative Example 9, even when the average grain size of the abrasive grains was 44 nm, which was smaller than 68 nm, the polishing liquid contained polyoxyethylene sorbitan fatty acid ester in an amount of 0.005% by mass or more. By containing, generation | occurrence | production of the vibration of a grinding | polishing apparatus was suppressed at the CMP process, and the to-be-polished surface containing sapphire was able to be smoothly grind | polished at a high grinding | polishing speed.

  A sapphire polishing liquid (CMP polishing liquid), a storage liquid, and a polishing method using these are suitable for CMP of a surface to be polished containing sapphire, and display an electronic device such as an LED base or a smartphone. It is suitable for CMP of a sapphire substrate (substrate having a polished surface containing sapphire) used for a part cover.

Claims (7)

Containing polyoxyethylene sorbitan fatty acid ester, abrasive grains containing silica, and liquid medium,
The polishing liquid for sapphire whose content of the said polyoxyethylene sorbitan fatty acid ester is 0.005 mass% or more on the basis of the total mass of polishing liquid.   The polishing liquid according to claim 1 whose pH is 7.0-10.5. The silica is colloidal silica;
The polishing liquid according to claim 1 or 2, wherein the abrasive grains have an average particle diameter of 20 to 160 nm.   The polishing liquid according to any one of claims 1 to 3, wherein the content of the abrasive grains is 1 to 40% by mass based on the total mass of the polishing liquid. A storage liquid for obtaining the polishing liquid according to any one of claims 1 to 4,
A storage liquid in which the polishing liquid is obtained by diluting with a liquid medium.   A grinding | polishing method provided with the process of grind | polishing the to-be-polished surface containing sapphire using the polishing liquid as described in any one of Claims 1-4. A polishing method comprising a step of polishing a surface to be polished containing sapphire using a polishing liquid obtained by diluting the storage liquid according to claim 5 with a liquid medium.