WO2020066998A1 - Polishing liquid, concentrate of same, method for producing polished article using polishing liquid, and polishing method of substrate using polishing liquid - Google Patents

Abstract

This polishing liquid is used for polishing of a siliceous substrate that has a surface roughness Ra of from 0.01 μm to 0.2 μm (inclusive). This polishing liquid contains ceria abrasive grains, silica abrasive grains and water. The average particle diameter D50 of the ceria abrasive grains is from 120 nm to 550 nm (inclusive). The average particle diameter D50 of the silica abrasive grains is from 40 nm to 140 nm (inclusive). The mass ratio of the silica abrasive grains to the ceria abrasive grains in the polishing liquid, namely the value of (silica abrasive grains)/(ceria abrasive grains) is from 4/100 to 150/100 (inclusive). The content of the ceria abrasive grains in the polishing liquid is from 0.25% by mass to 2.5% by mass (inclusive). The content of the silica abrasive grains in the polishing liquid is from 0.1% by mass to 1.5% by mass (inclusive).

Description

Polishing liquid, concentrated liquid thereof, method for producing polished article using polishing liquid, and method for polishing substrate using polishing liquid

The present invention relates to a polishing liquid for a substrate made of a siliceous material. The present invention also relates to a concentrated solution of the polishing liquid, a method for producing a polishing article using the polishing liquid, and a method for polishing a substrate using the polishing liquid.

In recent years, image sensors for mobile terminals such as smartphones have been required to have a thin sensor including a cover glass for the purpose of thinning the terminal. For this purpose, the cover glass of the image sensor is thinned by grinding, and then smoothed by finish polishing so that the glass surface does not have scratches or the like.

(4) It is known to use a polishing liquid containing ceria abrasive grains and silica particles for the purpose of polishing a glass substrate (see Patent Document 1). According to the same document, according to this polishing liquid, in polishing an amorphous glass substrate, it is possible to improve the polishing rate and reduce the surface roughness, pits, and scratches on the substrate surface after polishing. I have.

JP 2012-143845 A

However, even when the polishing liquid described in Patent Document 1 is used, depending on the surface state of the glass substrate, it may take a long time for polishing. Therefore, an object of the present invention is to provide a polishing liquid capable of improving a polishing rate when final polishing a glass substrate after grinding or the like.

The present inventors have earnestly studied and as a result, when finish polishing a siliceous substrate having a predetermined surface state, a ceria abrasive having a predetermined particle size and a silica abrasive having a predetermined particle size are used. It has been found that the above problem can be solved by using a polishing liquid containing a predetermined content of each abrasive grain in a predetermined range in the polishing liquid.

The present invention is a polishing liquid used for polishing a substrate made of a siliceous material having a surface roughness Ra specified in JIS B0601 of 0.01 μm or more and 0.2 μm or less.
The present invention may include ceria abrasive grains, silica abrasive grains, and water.
It is preferable that the average particle size _{D 50} of the ceria abrasive grains is 120nm or more 550nm or less.
It is preferable that the average particle size _{D 50} of the silica abrasive is 40nm or more 140nm or less.
It is preferable that a value of silica abrasive grains / ceria abrasive grains, which is a mass ratio of the silica abrasive grains to the ceria abrasive grains, is not less than 4/100 and not more than 150/100.
It is preferable that the content of the ceria abrasive is 0.25% by mass or more and 2.5% by mass or less.
It is preferable that the content of the silica abrasive is 0.1% by mass or more and 1.5% by mass or less.
The object has been achieved by providing a polishing liquid of the present invention having the above-described configuration.

Further, the concentrated solution for preparing a polishing slurry of the present invention may contain ceria abrasive grains, silica abrasive grains, and water.
It is preferable that the average particle size _{D 50} of the ceria abrasive grains is 120nm or more 550nm or less.
It is preferable that the average particle size _{D 50} of the silica abrasive is 40nm or more 140nm or less.
It is preferable that a value of silica abrasive grains / ceria abrasive grains, which is a mass ratio of the silica abrasive grains to the ceria abrasive grains, is not less than 4/100 and not more than 150/100.
The polishing slurry preparation concentrate is diluted with water to polish a substrate made of a siliceous material having a surface roughness Ra defined by JIS B0601 of 0.01 μm or more and 0.2 μm or less. It is used as a polishing liquid.
The concentration of the ceria abrasive grains in the polishing slurry is 0.25% by mass or more when the polishing slurry preparation concentrated solution is diluted 5 to 50 times with water to obtain a polishing solution. It is preferable to contain the silica abrasive grains and the ceria abrasive grains in an amount of not more than 0.5% by mass and the content of the silica abrasive particles being not less than 0.1% by mass and not more than 1.5% by mass.

Further, the present invention provides a method for manufacturing a polishing-processed article, comprising a step of polishing a substrate made of a siliceous material having a surface roughness Ra prescribed in JIS B0601 of 0.01 μm or more and 0.2 μm or less using a polishing liquid. Is the way. The present invention provides a method for producing a polishing treatment article, wherein the polishing liquid is used as the polishing liquid, or a polishing liquid obtained by diluting the concentrated liquid for preparing a polishing slurry with water is used. is there.

Further, the present invention is a method for polishing a substrate, comprising a step of polishing a substrate made of a siliceous material having a surface roughness Ra specified in JIS B0601 of 0.01 μm or more and 0.2 μm or less using a polishing liquid. . The present invention provides a method for polishing a substrate, wherein the polishing liquid is used as the polishing liquid, or a polishing liquid obtained by diluting the concentrated liquid for preparing a polishing slurry with water is used.

Hereinafter, the present invention will be described based on preferred embodiments. The polishing liquid of the present invention is used for polishing a substrate having a surface roughness Ra prescribed in JIS B0601 of 0.01 μm or more and 0.2 μm or less. This substrate is made of a siliceous material. Hereinafter, for simplicity, a substrate to be polished in the present invention is also referred to as a “silica substrate”. The processing means for realizing the surface state of the siliceous substrate is not particularly limited as long as the surface roughness Ra is in the range of 0.01 μm to 0.2 μm. Examples of the processing means include a grinding process using a grindstone and a lapping process. As a result of the study by the present inventors, when the surface roughness Ra of the substrate made of a siliceous material is in the above-mentioned range and the substrate is finish-polished with a polishing liquid described later, a surprisingly high polishing rate is achieved. Turned out to be. From this viewpoint, the surface roughness Ra of the siliceous substrate subjected to the final polishing is preferably 0.2 μm or less, more preferably 0.1 μm or less. The lower limit of the surface roughness Ra is preferably 0.01 μm or more, and more preferably 0.02 μm or more, from the relationship with the surface roughness after the finish polishing. The finish polishing is an operation for bringing the surface roughness Ra of the object to be polished to a surface state of 0.003 μm or less.

(4) The surface roughness Ra of the siliceous substrate is measured by AFM “Model No .: DIMENSION Icon” (manufactured by Bruker) according to JIS B0601. The measurement results are analyzed using the company's software "Nanoscope @ Analysis". The measurement conditions are as follows: measurement range: 10 μm × 10 μm, measurement point: 256 lines, scan rate: about 1 Hz.

As described above, the substrate is made of a siliceous material. "Silica material" refers to an inorganic polymer having silica (SiO ₂ ) as a repeating unit. The siliceous material may be crystalline or amorphous. The crystalline siliceous material includes quartz, for example. On the other hand, examples of the amorphous siliceous material include siliceous glass materials such as silicate glass, quartz glass, alkali silicate glass, soda-lime glass, borosilicate glass, and lead glass, but are not limited thereto. Absent.

研磨 The polishing liquid of the present invention used for polishing the above-mentioned siliceous substrate preferably contains ceria abrasive grains, silica abrasive grains, and water. Hereinafter, these components will be described in detail.

The ceria abrasive grains are preferably made of cerium oxide (CeO ₂ ) particles. As the ceria abrasives, those obtained by various known production methods can be used without particular limitation. For example, cerium oxide particles obtained by using a high-purity cerium carbonate salt or a high-purity cerium nitrate salt having a purity of 99% by mass or more as a starting material, calcining and pulverizing them, can be used. Alternatively, colloidal ceria obtained by preparing an aqueous slurry of cerium hydroxide, placing the slurry in an autoclave, and performing a hydrothermal treatment at a temperature of 100 ° C. or more under autogenous pressure can be used.

Ceria abrasive grains, from the viewpoint of improving the polishing rate at the time of the finish polishing, the average particle diameter _{D 50} is preferably at 120nm than 550nm or less, further preferably 350nm or more 520nm or less, 380 nm or more 500nm or less Is particularly preferred. The average particle size D ₅₀ is a volume cumulative particle size at a cumulative volume of 50% by volume, which is a measurement method suitable for measuring each particle size distribution range, such as a laser diffraction scattering type particle size distribution measuring method or a dynamic light scattering type particle size distribution measuring method. D is that of _50. Hereinafter, “D ₅₀ ” means the particle size measured by these methods.

The content of ceria abrasive grains in the polishing liquid is preferably from 0.25% by mass to 2.5% by mass, and more preferably from 0.5% by mass to 2.5% by mass, from the viewpoint of improving the polishing rate at the time of final polishing. The content is more preferably 0% by mass or less, particularly preferably 1.0% by mass or more and 1.5% by mass or less.

The silica abrasive used together with the ceria abrasive preferably comprises silicon dioxide (SiO ₂ ) particles. Examples of the silica abrasive grains include colloidal silica particles, fumed silica particles, and silica particles whose surface has been modified. Colloidal silica particles can be preferably used as the silica abrasive from the viewpoint of suppressing polishing scratches that may occur during the final polishing.

As the colloidal silica particles, those obtained by various known production methods can be used without particular limitation. For example, those obtained by a water glass method in which an alkali metal silicate such as sodium silicate is used as a raw material, and this is subjected to a condensation reaction in water to grow particles are used. Alternatively, those obtained by an alkoxysilane method in which an alkoxysilane such as tetraethoxysilane or the like is used as a raw material and a condensation reaction is carried out in water containing a water-soluble organic solvent such as alcohol to grow the same.

From the viewpoint of improving the polishing rate at the time of the finish polishing, the silica abrasive has an average particle diameter _{D 50,} is preferably 40nm or more 140nm or less, more preferably 60nm or more 120nm or less, 70 nm or more 100nm or less Is particularly preferred.

The content of the silica abrasive grains in the polishing liquid is preferably from 0.1% by mass to 1.5% by mass, and more preferably from 0.5% by mass to 1.5% by mass, from the viewpoint of improving the polishing rate at the time of final polishing. The content is more preferably 2% by mass or less, particularly preferably 0.8% by mass or more and 1.0% by mass or less.

Although the content of each of the silica abrasive grains and the ceria abrasive grains in the polishing liquid is in the above-described range, the value of silica abrasive grains / ceria abrasive grains, which is the mass ratio of silica abrasive grains to ceria abrasive grains, is also at the time of final polishing. It contributes to the improvement of the polishing rate. In this respect, the value of silica abrasive grains / ceria abrasive grains is preferably from 4/100 to 150/100, more preferably from 50/100 to 120/100, and more preferably from 80/100 to 100/100. It is particularly preferred that:

研磨 The polishing liquid of the present invention may contain abrasive grains other than ceria abrasive grains and silica abrasive grains as long as the effects of the present invention are not impaired. However, from the viewpoint of making the effect of improving the polishing rate when the final polishing of the siliceous substrate after grinding or the like performed more remarkable, the abrasive grains contained in the polishing liquid are ceria abrasive grains and silica. It is preferable that only abrasive grains are used.

Examples of the water include distilled water, ion-exchanged water, pure water, ultrapure water, and the like. The content of water in the polishing liquid is preferably 95% by mass or more and 98% by mass or less from the viewpoint of improving the polishing rate when performing final polishing. The polishing liquid of the present invention may contain a liquid medium other than water as long as the effects of the present invention are not impaired, but the effect of improving the polishing rate when final polishing the siliceous substrate is more remarkable. In light of this, the liquid medium is preferably water only.

研磨 The polishing liquid may contain additives as required in addition to the components described above. Examples of the additive include a pH adjuster, a viscosity adjuster, a chelating agent, an antifoaming agent, a surfactant, a rust inhibitor, a preservative, and the like. These components can be used alone or in combination of two or more.

The polishing liquid of the present invention can be prepared by, for example, stirring and mixing additives such as ceria abrasive grains, silica abrasive grains and, if necessary, a pH adjuster with water. The order of mixing the components, the temperature at the time of mixing, the mixing time, and the like are not particularly limited.

In the present invention, a polishing liquid containing ceria abrasive grains and silica abrasive grains having the above-mentioned concentrations is prepared by preparing a polishing slurry-preparing concentrate in advance and diluting the concentrate with water at a predetermined magnification. You may. By preparing a concentrated liquid instead of directly preparing the above-mentioned polishing liquid, there is an advantage that costs related to storage, transportation, storage and the like can be suppressed. The concentrated liquid can be diluted just before polishing to obtain a polishing liquid. Alternatively, the concentrated liquid and water may be supplied onto a polishing platen used for finish polishing, and the polishing liquid may be prepared on the polishing platen.

It is preferable that the concentrated liquid is diluted with water to 5 times or more and 50 times or less to obtain a polishing liquid. The dilution factor of X means that 1 part by mass of the concentrated solution is diluted by adding X-1 part by mass of water. When the concentrated liquid is diluted with water at a predetermined magnification to obtain a polishing liquid, the content of the ceria abrasive in the polishing liquid is in the above-mentioned range. Contains. Further, the value of silica abrasive grains / ceria abrasive grains, which is the mass ratio of silica abrasive grains to ceria abrasive grains in the concentrated liquid, is the same as the above-described value of silica abrasive grains / ceria abrasive grains in the polishing liquid.

理由 The reason why the effect of improving the polishing rate when the finish polishing is performed with the polishing liquid of the present invention is not clear, but is presumed as follows. That is, while the chemical polishing force due to the solid phase reaction of ceria particles is hard to act due to the collapse of the crystal phase on the substrate surface, the physical polishing force of the silica particles acts by adding silica particles, The phase is adjusted earlier, the chemical polishing power by the solid-phase reaction of the ceria particles is promoted, and the polishing rate when polishing a substrate having a surface roughness of 0.2 μm or less is improved. However, the mechanism is presumed, and the present invention is not construed as being limited to the mechanism.

In the present invention, a polishing method for polishing a siliceous substrate using the above polishing liquid is performed. In addition, a polished article is manufactured by polishing a siliceous substrate using the above-described substrate. When performing such a polishing method or when manufacturing a polished article, an ordinary polishing apparatus can be used. As the polishing apparatus, a single-side polishing apparatus having a carrier for holding a substrate and a polishing pad to which a polishing cloth is fixed, a double-side polishing apparatus, or the like can be used. A single-side polishing apparatus holds a substrate with a carrier and, while dropping the polishing liquid onto a polishing pad fixed on a surface plate provided in the apparatus, moves the substrate and the polishing pad relative to each other so that the one side of the substrate is moved. Is a device for polishing. Double-side polishing apparatus holds the substrate with a carrier, while dropping the polishing liquid between the polishing pad fixed to the upper surface plate provided in the apparatus and the polishing pad fixed to the lower surface plate, the substrate and This is a device for polishing both surfaces of a substrate by relatively moving a polishing pad. The substrate is polished by the physical action of friction between the polishing pad, the polishing liquid and the substrate, and the chemical action of the polishing liquid on the substrate.

The polishing pad is not particularly limited, and a pad made of a material such as a polyurethane type, a nonwoven fabric type, and a suede type may be used.

Before the silica-based substrate is finish-polished with the polishing liquid, it is subjected to a grinding step using a grindstone or a lapping step (rough polishing step). As a result, the surface roughness Ra of the silica substrate is adjusted to 0.01 μm or more and 0.2 μm or less. Finish polishing is preferably performed immediately after these steps. The term “immediately after” means that no step is interposed between the processing step using the grindstone and the finish polishing step using the polishing liquid of the present invention.

(4) When finish polishing the siliceous substrate using the polishing apparatus, the siliceous substrate immediately after the surface roughness Ra is adjusted to 0.01 μm or more and 0.2 μm or less is held by the holder. Then, the polishing pad is pressed against the surface of the siliceous substrate at a predetermined pressure while supplying the polishing liquid of the present invention between the siliceous substrate and the polishing pad. By rotating the polishing pad and / or the holder in this state, the silica substrate is finish-polished.

From the viewpoint of cost, the supply amount of the polishing liquid between the siliceous substrate and the polishing pad is preferably 0.07 mL / min or more and 0.64 mL / min or less per 1 cm ² of the surface of the substrate, More preferably, it is 0.21 mL / min or more and 0.5 mL / min or less. The pressure (polishing load) for pressing the polishing pad against the siliceous substrate is preferably 20 kPa or more and 30 kPa or less, and more preferably 23 kPa or more and 28 kPa or less, from the viewpoint of the load resistance of the substrate. The rotation speed of the polishing pad varies depending on the specific type of the siliceous substrate and the polishing apparatus to be used, but is generally preferably 30 rpm or more and 80 rpm or less, and more preferably 45 rpm or more and 65 rpm or less. preferable.

Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to such embodiments. Unless otherwise specified, “%” means “% by mass”.

[Example 1]
The ceria abrasive having an average particle diameter D ₅₀ of 150 nm and the silica abrasive having an average particle diameter D ₅₀ of 80 nm are stirred and mixed with distilled water to adjust the content of the ceria abrasive to 1.0%. In addition, a polishing liquid in which the content of silica abrasive grains was adjusted to 1.0% was obtained.

[Examples 2 to 21, and Comparative Examples 1 to 10]
Except that the average particle diameter D ₅₀ and the content of ceria abrasive and silica abrasive and to the values shown in Table 1 were prepared the polishing solution in the same manner as in Example 1.

[Evaluation]
The polishing amount of the final polishing using the polishing liquids of Examples 1 to 21 and the polishing liquids of Comparative Examples 1 to 10 was measured by the following method.

<Preparation of silica substrate after grinding>
A substrate made of borosilicate glass plate glass (Tempax glass manufactured by Shot Co., Germany, diameter 12 inches, thickness 700 μm) was prepared. This substrate was ground using a polishing machine “DGP8761CMP” (product name) manufactured by Disco Corporation. After grinding to a position of 50μm from the surface of the substrate using a grinding wheel of # 320 resin bond in the roughing-up section, the substrate is then transferred to the finish grinding section, and a grinding wheel of # 1000 resin bond is applied to the grinding wheel. Then, the surface was further ground to a position of 30 μm from the ground surface to make the surface roughness Ra 0.15 μm.

<Polishing of silica substrate after grinding>
The ground substrate was finish-polished using a polishing liquid. "DGP8761CMP" (product name) manufactured by Disco Corporation was used for the polishing apparatus, and "S-PAD" (product name) manufactured by the company was used for the polishing pad. The polishing conditions were as follows. After the substrate after the final polishing was washed and dried, the change in weight was measured using “GF-600” (product name) manufactured by AND Corporation, and the polishing amount (μm) was calculated. The results are shown in Table 1 below. The surface roughness Ra of the substrate after the finish polishing was 0.001 μm.
Polishing condition ・ Rotation speed of polishing pad: 500 rpm
・ Rotation speed of substrate: 505 rpm
・ Polishing load: 25kPa
・ Supply rate of polishing liquid: 250 mL / min (0.35 mL / min per 1 cm ^{2 of} polishing target surface)
・ Polishing time: 2 minutes

と お り As is clear from the results shown in Table 1, the polishing amount when the polishing substrate of each example was finish-polished using the polishing liquid of each example was larger than that when the polishing liquid of the comparative example was used. When the polishing liquids of Comparative Examples 1 to 4, 6, 9, and 10 were used, the polishing amount was reduced due to the fact that the polishing liquid contained only ceria abrasive grains and no silica abrasive grains. Is decreasing. When the polishing liquid of Comparative Example 5 was used, the polishing amount was small due to the excessively small particle size of the silica abrasive grains. When the polishing liquids of Comparative Examples 7 and 8 were used, the polishing amount was small due to the excessively large content of ceria abrasive grains.

According to the present invention, the polishing rate when the substrate made of the siliceous material is finish-polished after grinding or the like is improved.

Claims (4)

A polishing liquid used for polishing a substrate made of a siliceous material having a surface roughness Ra defined by JIS B0601 of 0.01 μm or more and 0.2 μm or less,
Including ceria abrasive grains, silica abrasive grains, and water,
The average particle diameter _{D 50} of the ceria abrasive grains is at 120nm than 550nm or less,
The average particle diameter _{D 50} of the silica abrasive is at 40nm or more 140nm or less,
The value of silica abrasive grains / ceria abrasive grains, which is the mass ratio of the silica abrasive grains to the ceria abrasive grains, is 4/100 or more and 150/100 or less,
The content of the ceria abrasive is 0.25% by mass or more and 2.5% by mass or less,
A polishing liquid wherein the content of the silica abrasive grains is 0.1% by mass or more and 1.5% by mass or less. Ceria abrasive, silica abrasive, and a polishing slurry preparation concentrate containing water,
The average particle diameter _{D 50} of the ceria abrasive grains is at 120nm than 550nm or less,
The average particle diameter _{D 50} of the silica abrasive is at 40nm or more 140nm or less,
The value of silica abrasive grains / ceria abrasive grains, which is the mass ratio of the silica abrasive grains to the ceria abrasive grains, is 4/100 or more and 150/100 or less,
The polishing slurry preparation concentrate is diluted with water to polish a substrate made of a siliceous material having a surface roughness Ra defined by JIS B0601 of 0.01 μm or more and 0.2 μm or less. It is used as a polishing liquid,
The concentration of the ceria abrasive grains in the polishing slurry is 0.25% by mass or more when the polishing slurry preparation concentrated solution is diluted 5 to 50 times with water to obtain a polishing solution. Preparation of a polishing slurry containing the silica abrasive grains and the ceria abrasive grains in an amount of 0.5% by mass or less and a content of the silica abrasives of 0.1% by mass or more and 1.5% by mass or less. Concentrate. A method for producing a polished article, comprising a step of polishing a substrate made of a siliceous material having a surface roughness Ra defined by JIS B0601 of 0.01 μm or more and 0.2 μm or less using a polishing liquid,
A method for producing a polishing-treated article, wherein the polishing liquid according to claim 1 is used as the polishing liquid, or a polishing liquid obtained by diluting the concentrated liquid for preparing a polishing slurry according to claim 2 with water. A method for polishing a substrate made of a siliceous material, comprising the step of polishing a substrate having a surface roughness Ra defined by JIS B0601 of 0.01 μm or more and 0.2 μm or less using a polishing liquid,
As the polishing liquid, a polishing liquid according to claim 1 or a polishing liquid obtained by diluting the concentrated liquid for preparing a polishing slurry according to claim 2 with water is used. Polishing method.