JP5997235B2 - Composite abrasive, manufacturing method thereof, polishing method and polishing apparatus - Google Patents

Description

The present invention relates to composite abrasive grains used for polishing the surface of sapphire, a manufacturing method thereof, a polishing method, a polishing apparatus, and a slurry used for polishing.

  In the manufacturing process of a semiconductor device, a polishing process (lapping) is performed to flatten the surface of a substrate (Semiconductor substrate). One conventionally employed method is to polish a sapphire substrate using an oily slurry containing diamond abrasive grains. The substrate surface is mechanically scraped by slurry and diamond abrasive grains sandwiched between a sapphire substrate and a metal surface plate. Diamond abrasive grains are harder than sapphire substrates. Therefore, this method has a high polishing rate and can reach the target polishing amount in a short time. However, since a large scratch may be generated on the substrate surface of the sapphire substrate, it is difficult to obtain a high-quality polished surface.

  In order to solve the above problems, various techniques employing mechanochemical polishing methods have been introduced (Patent Document 1) (Patent Document 2).

JP 2005-81485 A WO2011136367

  The dry polishing method disclosed in Patent Document 1 generates high frictional heat and promotes mechanochemical polishing to improve the polishing rate. However, polishing scraps and abrasives exposed to a high temperature adhere to the inside of the polishing apparatus. Therefore, there has been a problem that it takes a long time to clean the polishing apparatus. On the other hand, the wet polishing method disclosed in Patent Document 2 promotes mechanochemical polishing using a strong alkaline slurry to improve the polishing rate. However, a strongly alkaline slurry having a pH of 10 to 14 deteriorates the working environment and increases the cost of waste liquid treatment.

  Furthermore, in the known method using diamond abrasive grains, the oily slurry is denatured by the heat of the polishing process, so that the abrasive grains aggregate. As a result, there is a problem that expensive diamond abrasive grains cannot be reused as they are.

In order to solve the above problems, an object of the present invention is to provide composite abrasive grains suitable for high-quality polishing of sapphire using wet polishing and utilizing mechanochemical action, and a method for producing the same.
Furthermore, an object of this invention is to provide the grinding | polishing method and polishing apparatus which wet-polish sapphire using the slurry with little influence on an environment.

  The following configurations are means for solving the above-described problems.

<Configuration 1>
Abrasive grains for wet polishing sapphire,
A particulate first abrasive having a Mohs hardness of 7 to 9,
A particulate second abrasive having a mechanochemical action on the material to be polished;
A mixture of particulate frictional heat reactants, which is sparingly soluble in pure water used for the slurry and made of an alkali metal salt or an alkaline earth metal salt,
It is directly bonded by mechanical alloy method and integrated into particles,
The frictional heat reactant _is selected from _{CaCO 3, SrCO 3, MgCO 3} , BaCO 3, Li 2 CO 3, Ca 3 (PO 4) 2, Li 3 PO 4 and AlK (SO _{4) 2} groups In addition, a composite abrasive comprising one or two or more materials and occupying 5 to 95 weight percent of the integrated particles.

<Configuration 2>
The composite abrasive according to Configuration 1, wherein the first abrasive is Al ₂ O ₃ , ZrSiO _4, or ZrO ₂ and occupies 5 weight percent or more and 95 weight percent or less of the integrated particles.

<Configuration 3>
The second abrasive is one or more materials selected from the group consisting of Cr ₂ O ₃ , Fe ₂ O ₃ and SiO ₂ , and is 5 weight percent of the integrated particles. The composite abrasive grain according to Configuration 1, occupying 95 weight percent or less.

<Configuration 4>
The composite abrasive grain according to Configuration 1, wherein when the SiO ₂ is selected as the second abrasive, one having a Mohs hardness greater than that of SiO ₂ is selected as the first abrasive.

  Delete

<Configuration 5>
Abrasive grains for wet polishing sapphire,
A particulate first abrasive having a Mohs hardness of 7 to 9,
A particulate second abrasive having a mechanochemical action on the material to be polished;
A mixture of particulate frictional heat reactants, which is sparingly soluble in pure water used for the slurry and made of an alkali metal salt or an alkaline earth metal salt,
It is directly bonded by mechanical alloy method and integrated into particles,
The first abrasive is Al ₂ O ₃ , ZrSiO ₄ or ZrO ₂ ,
The second abrasive is one or more materials selected from the group consisting of Cr ₂ O ₃ , Fe ₂ O ₃ and SiO ₂ ,
The frictional heat reactant is selected from the group of CaCO ₃ , SrCO ₃ , MgCO ₃ , BaCO ₃ , Li ₂ CO ₃ , Ca ₃ (PO ₄ ) ₂ , Li ₃ PO ₄ and AlK (SO ₄ ) _2. Further, composite abrasive grains that are one kind or two or more kinds of materials.

<Configuration 6>
The 1st abrasive | polishing agent of the structure 1 or 5 and the 2nd abrasive | polishing agent and the frictional heat reaction agent were combined by the mechanical alloy method, and were integrated in the particle form of an average particle diameter of 0.05 micrometer or more and 100 micrometers or less. Composite abrasive.

<Configuration 7>
A composite in which the first abrasive, the second abrasive, and the frictional heat reactive agent according to Configuration 1 or 5 are combined by a mechanical alloy method to be integrated into particles having an average particle diameter of 0.05 μm to 100 μm. A manufacturing method of abrasive grains.

<Configuration 8>
A polishing method in which the material to be polished is wet-polished using a slurry in which the composite abrasive grain according to Configuration 1 or 5 is dispersed in pure water.

<Configuration 9>
The composite abrasive according to Configuration 1 or 5 , wherein when the slurry is constituted by dispersing the composite abrasive at a concentration of 15 weight percent in 100 ml of pure water, the pH at 25 degrees Celsius is 5 or more and 9 or less. A polishing method in which sapphire is wet-polished by selecting the composition of the grains.

<Configuration 10>
A slurry for wet polishing sapphire, wherein the apparent specific volume (static method) of the composite abrasive grain according to Configuration 1 or 5 is from 0.5 ml / g to 200 ml / g.

<Configuration 11>
An apparatus for supplying the slurry according to any one of Structures 8 to 10 onto a pad composed of any one of synthetic fiber, glass fiber, natural fiber, synthetic resin, and natural resin; A polishing apparatus comprising: a pressing device that generates pressure between the composite abrasive grains dispersed on the upper surface of the pad and the material to be polished.

<Configuration 12>
The composite abrasive grain according to Configuration 1 or 5 is dispersed and fixed on a pad made of synthetic fiber, glass fiber, natural fiber, synthetic resin, or natural resin, and pure water is put on the pad. A polishing apparatus comprising: a supply device; and a pressing device that presses the material to be polished against the pad with elasticity to generate friction between the composite abrasive grains dispersed on the upper surface of the pad and the material to be polished .

<Configuration 13>
13. The polishing apparatus according to Configuration 11 or 12 , wherein a temperature control device for adjusting the temperature of the polishing slurry is provided.

<Configuration 14>
The polishing apparatus according to Configuration 11 or 12 , comprising means for irradiating the composite abrasive with light.

<Effect of Configuration 1>
The two kinds of abrasives and the frictional heat reaction agent are directly bonded by mechanical energy and integrated into a particulate form. Since the binding energy between the particles is large, the abrasive grains are not decomposed during the polishing process. All the abrasive grains are exposed on the outer surface of the composite abrasive grains, and are in direct contact with the material to be polished during the polishing process. The frictional heat reactive agent reacts with the heat generated by the friction between the outer surface of the composite abrasive and the material to be polished, thereby promoting the mechanochemical action of the second abrasive and improving the polishing rate. Mechanical Nikaruaroi method is a best process for producing a composite abrasive grains bonded directly by mechanical energy.
<Effect of Configuration 9>
A slurry in which composite abrasive grains are dispersed in pure water has little influence on the environment.
<Effect of Configuration 11>
A composite abrasive grain having a specific gravity optimal for dispersion in pure water can be obtained.
<Effect of Configuration 12>
When the material to be polished is pressed against the pad using elasticity, the pressure between the composite abrasive grains dispersed on the upper surface of the pad and the material to be polished can be increased, and frictional heat can be effectively generated.
<Effect of Configuration 13>
Even if the composite abrasive grains are fixed on the pad and pure water is supplied, wet polishing can be performed.
<Effect of Configuration 14>
If the polishing slurry is heated in advance, the chemical reaction of the frictional heat reactant can be promoted. Further, when the slurry is circulated and used repeatedly, polishing treatment can be performed under an optimal constant temperature condition.
<Effect of Configuration 15>
The chemical reaction can be promoted by the excitation action of the abrasive grains with light.

It is an Example schematic structure figure of the composite grain of the present invention. It is a schematic perspective view which shows the Example of a grinding | polishing apparatus. It is explanatory drawing of the known mechanochemical polishing method. 2 is a photomicrograph showing the surface condition of the composite abrasive grain of Example 1 before and after polishing. It is the figure which compared the component of the composite abrasive grain before and behind grind | polishing a sapphire substrate for 4 hours. It is a table | surface which shows the pH measurement result of the slurry after a grinding | polishing process. It is a comparison figure of the result of having polished sapphire using various abrasive grains. It is a table | surface which shows the relationship between the temperature of the slurry after grinding | polishing, and a polishing rate. It is the data which shows the relationship between the polishing pressure and polishing rate of samples 1-3.

FIG. 1 is a schematic structural diagram of an embodiment of the composite abrasive grain of the present invention.
The composite abrasive grain 10 of the present invention is used for polishing sapphire . As shown in FIG. 1, the composite abrasive grain 10 of the present invention is obtained by directly bonding a first abrasive 13, a second abrasive 13, and a frictional heat reactive agent 14. This composite abrasive grain 10 is integrated in the form of particles. Direct bonding means that no bonding material such as an adhesive is used.

  Being integrated in the form of particles means that the size and shape suitable for the use as abrasive grains are selected. For example, for lapping sapphire substrates, when the required surface roughness is 0.01 μm or less, the average grain size of the composite abrasive grains is selected to be 10 μm or less. The composite abrasive grains of the present invention can be produced in the form of particles having an average particle diameter of 0.05 μm or more and 100 μm or less. Therefore, various surface roughness requirements can be met.

The first abrasive 12 is in the form of particles having a Mohs hardness of 7 or more and 9 or less. The reason why the Mohs hardness is 7 or more is to provide the minimum hardness necessary for polishing sapphire . The reason why the Mohs hardness is set to 9 or less is to use particles having a hardness equal to or lower than that of the material to be polished and to polish the material to be polished without causing a large scratch. For example, α-Al ₂ O ₃ , γ-Al ₂ O _3, ZrSiO _4, or cubic ZrO ₂ is suitable for the first abrasive 12.

  The first abrasive 12 preferably occupies 5 weight percent or more and 95 weight percent or less when the total weight of the integrated particles is 100. If the blending ratio of the first abrasive 12 is less than 5%, the hardness of the composite abrasive is insufficient. Further, if the blending ratio of the first abrasive 12 exceeds 95%, the polishing rate cannot be accelerated by chemical action.

  The second abrasive 13 is a particle having a mechanochemical action on the material to be polished. The mechanochemical action means that a mechanical grinding function is exhibited while chemically changing the material to be polished. This is because the polishing process is performed at a high polishing rate (removal rate, polishing amount per unit time) without causing large scratches on the polished surface.

As the second abrasive 13, one or more materials are selected and used from chromium oxide (Cr ₂ O ₃ ), ferric oxide (Fe ₂ O ₃ ), and silica (SiO ₂ ). It is preferable.

The material selected as the second abrasive 13 is, for example, a material that easily undergoes isomorphous substitution with aluminum ions (Al ₃ ⁺ ) of sapphire. Both are materials whose ionic radii approximate to aluminum (Al). On the other hand, silica (SiO ₂ ) causes substitution that occurs during dehydration of siloxane. By these chemical reactions, the surface of the material to be polished is denatured, and polishing can be efficiently performed with the first abrasive having a hardness equal to or lower than that of the material to be polished.

When silica (SiO ₂ ) is used for the second abrasive 13, it is preferable to select the first abrasive 12 having a Mohs hardness greater than that of SiO ₂ . The reason is clarified by the difference in the effect of the polishing process described in FIG.

  The second abrasive 13 preferably occupies 5 weight percent or more and 95 weight percent or less when the total weight of the integrated particles is 100. If the blending ratio of the second abrasive 13 is less than 5%, a sufficiently high polishing rate cannot be maintained. If the blending ratio of the second abrasive 13 exceeds 95%, the first abrasive 12 is insufficient and the hardness of the composite abrasive grain is insufficient. Further, the effect of promoting the polishing rate by the frictional heat reactant 14 becomes insufficient.

  The frictional heat reactant 14 is hardly soluble in pure water used as a slurry, and is made of an alkali metal salt or an alkaline earth metal salt. The frictional heat reactant 14 is not a liquid but a solid. If the frictional heat reactive agent 14 is a solid, it can be integrated with the first abrasive 12 and the second abrasive 13 by mechanical energy to obtain composite abrasive grains. When the frictional heat reactant 14 is a liquid or a material that is easily dissolved in water, the composite abrasive grains decompose in the slurry. Furthermore, the waste liquid has an adverse effect on the environment.

The frictional heat reactant 14 is selected from the group of CaCO ₃ , SrCO ₃ , MgCO ₃ , BaCO ₃ , Li ₂ CO ₃ , Ca ₃ (PO ₄ ) ₂ , Li ₃ PO ₄ and AlK (SO ₄ ) _2. In addition, it is preferable to use one or more materials. Any material can promote the polishing function of the second abrasive 13 by frictional heat generated during polishing.

Specifically, the materials selected as the frictional heat reactant 14 have a solubility in pure water of 0.1 or less, excluding LiCO ₃ and AlK (SO ₄ ) ₂ . That is, the amount dissolved in 100 grams of pure water at 25 degrees Celsius is 0.1 grams or less.

On the other hand, the solubility of LiCO ₃ is 1.33 and the solubility of AlK (SO ₄ ) ₂ is 6.74, which is easier to dissolve in water than other materials. However, when used as composite abrasive grains, none of them are separated during polishing and dissolved in a large amount in pure water. That is, this degree of solubility is acceptable. Therefore, the composite abrasive grains could be circulated and used repeatedly. In the present invention, poorly soluble means that the amount dissolved in 100 grams of pure water at 25 degrees Celsius is 7 grams (solubility 7) or less.

  The frictional heat reaction agent 14 preferably accounts for 5 to 95 percent when the total weight of the integrated particles is 100. If the blending ratio of the frictional heat reaction agent 14 is less than 5 weight percent, the effect of promoting the polishing function of the second abrasive 13 becomes insufficient. When the blending ratio of the frictional heat reactive agent 14 exceeds 95 weight percent, the amounts of the first abrasive 12 and the second abrasive 13 are insufficient.

  When the powder of the first abrasive 12, the powder of the second abrasive 13, and the powder of the frictional heat reaction agent 14 are uniformly mixed and mechanical energy is repeatedly applied, the particles are directly bonded mechanically. It becomes a shape. As a result, the composite abrasive shown in FIG. 1 is obtained. For example, mechanical energy can be given to these powders by a mechanical alloy method.

  In this composite abrasive grain, the first abrasive 12, the second abrasive 13, and the frictional heat reactive agent 14 are mechanically firmly bonded by intermolecular force or the like. The bonding strength is strong, and the first abrasive 12, the second abrasive 13, and the frictional heat reactant 14 do not separate even after being used for the polishing process. The second abrasive 13 and the frictional heat reactant 14 are only slightly consumed due to the chemical reaction. Therefore, the composite abrasive can be used repeatedly for polishing.

  Mixing the powder of the first abrasive 12, the powder of the second abrasive 13, and the powder of the frictional heat reaction agent 14, and crushing, rubbing, compressing, pulling, hitting, bending, or colliding When the impact is repeatedly applied, mechanical energy can be applied. Any kind of impact may be applied. Multiple types of impacts may be combined. For example, in the mechanical alloy method, a phenomenon occurs in which powder is crushed by mechanical impact, and then part of the powder is integrated and solidified into particles. There are theories of bonding by intermolecular forces, the theory of bonding by eutectic, and the theory of solidification in an amorphous state.

  As shown in FIG. 1, in the composite abrasive grains of the present invention, any mixed abrasive grains are exposed on the outer surface of the composite abrasive grains, and are in direct contact with the material to be polished during the polishing process. The frictional heat reactant reacts with the heat generated by the friction between the outer surface of the composite abrasive grains and the material to be polished, thereby promoting the mechanochemical action and greatly improving the polishing rate. Moreover, it is thought that several types of abrasive grains have an amorphous structure partially. Since the amorphous structure is thermodynamically non-equilibrium, it is considered that the chemical reaction is easily promoted. The action of the frictional heat reactant will be specifically described in the description of Examples.

FIG. 2 is a schematic perspective view showing an embodiment of the polishing apparatus of the present invention.
For example, the structure shown in this figure is suitable for a polishing apparatus using the composite abrasive grains of the present invention. The polishing surface plate 20 is driven to rotate in the direction of the arrow 32. The upper surface of the polishing surface plate 20 is covered with a polishing pad 22. The holding device 24 is a device for pressing and supporting the workpiece 26 (sapphire substrate) against the polishing pad 22. Slurry is supplied from the liquid injector 28 in the direction of the arrow 30. The slurry is obtained by dispersing composite abrasive grains in pure water. The material to be polished 26 pressed against the surface of the polishing pad 22 is polished by the composite abrasive grains. The slurry is supplied in a fixed amount continuously during the polishing process.

  The composite abrasive grain of the present invention can be used, for example, in a polishing process of a sapphire substrate for LED. The sapphire substrate has a Mohs hardness of 9. In the polishing process, for example, polishing is performed until the surface roughness of the sapphire substrate reaches 0.010 μm or less. When diamond abrasive grains are used for polishing a sapphire substrate, the diamond abrasive grains have a Mohs hardness higher than that of the sapphire substrate, so that a polishing mark (saw mark) is made. Therefore, the first abrasive 12 that is comparable to or softer than the sapphire substrate and the second abrasive 13 having a mechanochemical action are used.

  In the lapping step, for example, a polishing slurry in which the composite abrasive grains are dispersed at a concentration of 15 weight percent in 100 ml of pure water is used. The pH of the slurry at 25 degrees Celsius is 4 or more and 11 or less. Actually, the waste liquid after polishing for 4 hours was about pH 8. The pH of the waste liquid is most preferably 5 or more and 9 or less.

  The slurry preferably contains 5 weight percent or more of composite abrasive grains with respect to pure water 100. In that case, it is preferable to adjust so that the apparent specific volume (stationary method) of the composite abrasive grains is 0.5 ml / g or more and 200 ml / g or less. This optimizes the specific gravity of the composite abrasive. If the apparent specific volume (static method) is less than 0.5 ml / g, the composite abrasive grains settle in the slurry and the polishing rate becomes insufficient. Even if the apparent specific volume (the standing method) exceeds 200 ml / g, the polishing rate is not improved, and the composite abrasive grains become excessive in the slurry, resulting in intense aggregation.

  In the apparatus shown in FIG. 2, when the material 26 is pressed against the polishing pad 22 with elasticity, frictional heat is generated between the composite abrasive grains dispersed on the upper surface of the polishing pad 22 and the material 26. Easy to do. The frictional heat reacts actively with the frictional heat, and promotes the mechanochemical reaction of the second abrasive.

  In order to easily cause frictional heat, for example, it is preferable that the holding device 24 is made of a resilient rubber plate or the like. At the same time, the polishing pad 22 is preferably made of synthetic fiber, glass fiber, natural fiber, synthetic resin, natural resin or the like. By applying an appropriate elasticity, it is possible to effectively generate frictional heat and realize a high polishing rate. Alternatively, the composite abrasive grains 10 may be dispersed and fixed in advance on the polishing pad 22, and pure water or pure water in which composite abrasive grains are dispersed may be supplied onto the polishing pad 22.

  In addition, since the frictional heat does not accumulate at the beginning of starting the polishing apparatus, the temperature rise of the polishing surface of the material to be polished 26 becomes insufficient. This affects the polishing rate. Therefore, it is preferable to provide the polishing apparatus shown in FIG. 2 with a temperature control device 25 for adjusting the temperature of the slurry to an appropriate temperature. What is necessary is just to comprise the temperature control apparatus 25 with an electric heater, for example. Thereby, the optimum temperature condition can be set immediately after the start of polishing.

  In addition, the holding device 24 of the polishing apparatus of this embodiment is provided with several through holes 34. A light irradiation device 29 is disposed above the holding device 24. The main part longitudinal cross-sectional view is shown in the circle of the one-dot chain line on the left side of FIG. The light emitted from the light irradiation device 29 passes through the through hole 34 of the holding device 24, passes through the material to be polished 26, and is irradiated onto the composite abrasive grain 10. Since the holding device 24 rotates in the direction of the arrow 33, the irradiation light reaches the composite abrasive grains sandwiched between the material to be polished 26 and the polishing pad 22. By this light irradiation, the composite abrasive grain 10 is brought into an excited state and can react more efficiently.

FIG. 3 is an explanatory diagram of a known mechanochemical polishing method.
These are listed as comparative examples. The abrasive grains shown in FIG. 3A are a mixture of a plurality of types of abrasives. The A abrasive 16 and the B abrasive 18 are mixed and supplied to the polishing apparatus together with the slurry. The B abrasive 18 has a function of promoting the polishing action of the A abrasive 16. In this case, since the specific gravities of the A abrasive 16 and the B abrasive 18 are different, as shown in FIG. If they are mixed uniformly and do not contact the material to be polished, the polishing promoting effect cannot be exhibited.

  FIG. 3C shows an example in which a slurry 17 that promotes the polishing action of the A abrasive 16 is used. Since this method solves the above problems, it has been widely adopted in recent years. However, since a strongly alkaline solution is used for the slurry 17, the working environment is deteriorated. Furthermore, the cost of processing the waste liquid after the polishing process is large.

  FIG. 3D shows an example in which the A abrasive 16 is fixed to the surface of the polymer material 19. It is difficult to obtain such composite abrasive grains having an average particle size suitable for a lapping process for hard and brittle materials. That is, only a large size can be obtained. Moreover, specific gravity becomes light as a whole, and it will be pushed away from a grinding | polishing apparatus. Since the composite abrasive grains of the present invention have an appropriate specific gravity, the composite abrasive grains stay longer on the upper surface of the pad of the polishing apparatus and improve the polishing rate.

FIG. 4 is a photograph of the composite abrasive grain, and FIG. 4A is a photomicrograph showing the surface state of the composite abrasive grain of Example 1. FIG. 4B is a photomicrograph showing the surface state of the composite abrasive grains recovered after polishing the sapphire substrate for 4 hours.
The composite abrasive grain of Example 1 is obtained by integrating aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), and calcium carbonate (CaCO ₃ ). These were mixed at a ratio of 50 parts by weight, 37.5 parts by weight and 12.5 parts by weight, respectively. These were pulverized to a powder having an outer diameter of 1 μm or less by a ball milling method and further subjected to mechanical impact for about 0.5 hours to obtain composite abrasive grains. Among them, composite abrasive grains having an average particle size of 2 μm were selected and used.

  The composite abrasive grains obtained by the above method were supplied to the apparatus shown in FIG. 2 together with pure water, and the sapphire substrate was polished for 4 hours. The slurry containing the composite abrasive is supplied onto the polishing pad 22 during the polishing process and sequentially discharged. The discharged slurry is recovered again, supplied onto the polishing pad 22, and used repeatedly.

  As already described, the composite abrasive grain of the present invention has high mechanical strength and can be used repeatedly for a certain period of time because it is not destroyed by the polishing process. From the micrograph of the composite abrasive grain taken out of the slurry after polishing the sapphire substrate for 4 hours, it was found that most of the mixed material was present in its original form. About 3% of the total weight was consumed by the above chemical reaction.

FIG. 5 is a diagram comparing the components of the composite abrasive before and after polishing the sapphire substrate for 4 hours.
Prior to polishing, the proportions of aluminum (Al), silicon (Si), and calcium (Ca) in the total were 38.2 wt%, 43.8 wt%, and 17.9 wt%, respectively. After the polishing treatment, they were 41.2 wt%, 42.3 wt%, and 16.5 wt%. The ratio of the components other than the aluminum component to the whole was not substantially changed. The cause of the increase in the proportion of the aluminum component is considered to be that polishing scraps obtained by polishing sapphire were newly included.

  The residue discharged together with the slurry after polishing was separated and analyzed. As a result, a residue containing aluminum (Al), silicon (Si) and calcium (Ca) in the proportions of 52%, 33% and 0.5%, respectively, was obtained. As a result of component analysis, mullite was included.

  During the polishing process, it was examined whether the composite abrasive grains were mechanically or thermally decomposed to produce mullite or other causes. The amount of mullite produced was proportional to the polishing time. Moreover, an amount of mullite was generated that sufficiently exceeded the consumption of the composite abrasive before and after the polishing treatment. That is, it was found that the composite abrasive was polished while chemically altering the surface of the material to be polished, and the residue was mullite. Using any of the conventional wet polishing methods, this amount of mullite was not generated after 4 hours of polishing. Therefore, it was proved that the above-mentioned frictional heat reactive agent functions effectively during polishing.

Mullite is a compound of aluminum oxide and silicon dioxide. The chemical formula is represented by 3Al ₂ O ₃ .2SiO _{2 to} 2Al ₂ O ₃ .SiO ₂ , or Al ₆ O ₁₃ Si ₂ . Friction heat of several hundred degrees Celsius is locally generated by friction between the composite abrasive grains and the material to be polished. Although this heat is diffused by the slurry, the micro area where the composite abrasive grains and the material to be polished are in contact with each other becomes high temperature. It can be determined that calcium carbonate has generated mullite as a result of promoting the reaction between the material to be polished and aluminum oxide.

FIG. 6 is a table showing the pH measurement results of the slurry after the polishing treatment.
In both cases, a high polishing rate of 0.7 to 1.0 μm per minute was realized. When a material other than Li ₂ CO ₃ and Ca ₃ (PO ₄ ) ₂ is used as the frictional heat reactant, the measured value before polishing is pH 4.6 to 8.0, and the measured value after polishing is pH 4.2 to 4.2. It was within the range of 8.2. When Li ₂ CO ₃ and Ca ₃ (PO ₄ ) ₂ are used as frictional heat reactants, the measured values before polishing are pH 10.1 and 9.0, and the measured values after polishing are pH 11.2 and 9 respectively. .6. Both are in the range of weak acidity to weak alkalinity, and the adverse effect on the work environment can be suppressed. Moreover, the waste liquid treatment becomes simple. It was found that since the region of high alkali atmosphere at high temperature is a very small region, the pH of the slurry is not greatly affected.

FIG. 7 is a comparative view of the results of polishing sapphire using various abrasive grains.
The part indicated as Sample 1 shows the result of using composite abrasive grains in which Al ₂ O ₃ , SiO ₂ and CaCO ₃ are integrated for polishing sapphire. The part indicated as sample 2 shows the result of using composite abrasive grains in which Al ₂ O ₃ , Fe ₂ O ₃ and CaCO ₃ are integrated for polishing sapphire. The part indicated as Sample 3 shows the result of using composite abrasive grains in which Al ₂ O ₃ , Cr ₂ O ₃ and CaCO ₃ are integrated for polishing sapphire.

In this example, the sapphire wafer was polished with GC (green carbonite) having an average particle size of # 325, and a surface roughness Ra = 0.22 μm was used as the polishing target. The operating conditions of the polishing apparatus are: the rotation speed of the polishing surface plate 20 is 50 rotations per minute (rpm), the rotation speed of the holding device 24 is 100 rotations per minute, and the holding device 24 moves the material 26 to be polished in the direction of the polishing surface plate 20. The polishing pressure to be pressed against the surface was 160 grams per square centimeter (g / cm ² ). The composite abrasive is mixed in 15% by weight in pure water. The slurry thus adjusted was supplied onto the polishing pad 22 from the liquid injector 28 at 1 milliliter per minute (ml / min).

The following is a comparative example. ref1 shows the result of using only aluminum oxide (Al ₂ O ₃ ) as abrasive grains. ref2 shows the result of using only silicon oxide (SiO ₂ ) as abrasive grains. ref3 shows the result of using only calcium carbonate (CaCO ₃ ) as abrasive grains.

ref4 shows the result of using composite abrasive grains in which aluminum oxide (Al ₂ O ₃ ) and silicon oxide (SiO ₂ ) are mechanically bonded and integrated in the same manner as in the present invention. ref5 shows the result of using composite abrasive grains in which aluminum oxide (Al ₂ O ₃ ) and calcium carbonate (CaCO ₃ ) are mechanically bonded and integrated in the same manner as in the present invention.

ref6 shows the result of using composite abrasive grains in which silicon oxide (SiO ₂ ) and calcium carbonate (CaCO ₃ ) are mechanically bonded and integrated in the same manner as in the present invention. ref7 shows the result of using a simple mixture (not integrated) of aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ) and calcium carbonate (CaCO ₃ ) mixed in the slurry. ref8 shows the result of using diamond abrasive grains having an average particle diameter of 1 to 3 μm. In each of the above examples, a resin pad was used as a polishing pad, and a slurry in which abrasive grains were mixed in pure water was used. On the other hand, ref9 indicates the result of using diamond abrasive grains having an average particle diameter of 1 to 3 μm, using a metal surface plate in the polishing apparatus, and using an oily slurry.

  Here, when the polishing rates of all these examples are compared, when the composite abrasive grain of sample 1 is used, it is 1 μm per minute, whereas in the examples of ref1 to ref8, all are about It cannot exceed 0.3 μm. Even in the case of ref9, the polishing rate is 0.8 μm per minute, which is not equal to the polishing rate of the present invention. An example of ref9 is a method that is said to have the highest known polishing rate.

Samples 1 and 2 were able to achieve a higher polishing rate than any known method. In the case of sample 3, a polishing rate comparable to that of ref9 was achieved. All samples use a slurry using pure water as a dispersion medium, which does not deteriorate the working environment and can be easily treated as a waste liquid. In addition, when a metal surface plate is used, its surface must be as flat as required for the polished surface of sapphire. However, it is not easy to maintain the flatness. On the other hand, the resin pad is for applying pressure to press the composite abrasive grains against the polished surface of sapphire. Therefore, a highly accurate structure is not required. Resin pads are inexpensive and easy to maintain. The present invention, since a soft polishing pad such as a resin pad can use and has advantageously der than using a metal plate.

Here, the reason for the remarkable improvement in the polishing rate by the composite abrasive of the present invention will be described.
(1) An abrasive having a Mohs hardness of 7-9 was included in the composite abrasive grains. An abrasive having a Mohs hardness of 7-9 was ZrSiO ₄ , Al ₂ O _3, and ZrO ₂ . These abrasives function to form a plastic deformation layer (amorphous layer) by applying a physical force to the material to be polished. Further, these abrasives function to peel off the altered layer that has been altered by the mechanochemical abrasive.

α-Al ₂ O ₃ has a Mohs hardness of 9. γ-Al ₂ O ₃ has a Mohs hardness of 8. ZrSiO ₄ and ZrO ₂ have a Mohs hardness of 7.5 to 8.5. Since none of the abrasives has a Mohs hardness higher than that of the material to be polished, generation of polishing flaws is suppressed. In addition, the composite abrasive grains using Al ₂ O ₃ have a higher polishing rate than the composite abrasive grains using ZrSiO ₄ . It is considered that the crystal structure of the material to be polished is destroyed and the mechanochemical reaction is likely to occur.

(2) The mechanochemical abrasive was included in the composite abrasive grain. The mechanochemical abrasive was Cr ₂ O ₃ , Fe ₂ O ₃ or SiO ₂ . It is easy to cause isomorphous substitution with sapphire (Al ₂ O ₃ ). Isomorphous substitution is a phenomenon in which ions having similar ionic radii are replaced with each other when pressure or heat is applied from the outside.

Substances with an ionic radius close to that of sapphire six-coordination Al ₃ ⁺ (ionic radius 0.54 Å) are Fe ₂ O ₃ hexacoordinated Fe ₃ ⁺ (ionic radius 0.55 Å) and , Cr ₂ O ₃ hexacoordinate Cr ₃ ⁺ (ion radius 0.62 Å). These ion groups cause isomorphous substitution. This chemical reaction is thought to alter the polished surface of sapphire.

On the other hand, SiO ₂ undergoes the following chemical reaction. When SiO ₄ tetrahedrons having silanol groups (≡Si—OH) are linked by a dehydration condensation reaction, Al ₃ ⁺ is added to the dehydration condensation reaction in the form of Al (OH) ₃ . The SiO ₄ connector is incorporated into the crystal structure of sapphire. Inside the SiO ₄ linked body, hexacoordinate Si ₄ ⁺ (ionic radius 0.40Å) is replaced by four-coordinate Al ₃ ⁺ (ionic radius 0.39Å). It is thought that the chemical reaction due to this isomorphous substitution alters the polished surface of sapphire.

Due to the mechanochemical action of the second abrasive and the grinding action of the first abrasive, the polishing process can be performed without damaging the material to be polished. There is an effect that it forms a high-quality polished surface at a high polishing rate than conventional.

(3) Frictional Heat Reactant was Included in Composite Abrasive The chemical reaction when calcium carbonate (CaCO ₃ ) was used as the friction heat reactive agent will be described. Calcium carbonate is decomposed into CaO and CO ₂ by frictional heat generated by friction between the composite abrasive grains and the polished surface of the material to be polished. Further, when heat of several hundred degrees Celsius is generated by frictional heat, calcium oxide CaO reacts with water to generate heat, and calcium hydroxide (Ca (OH ₂ )) is generated. This reaction occurs only in a very narrow region where the material to be polished and the composite abrasive are in contact. This reaction changes the quality of the material to be polished. At the same time, it is considered that the chemical reaction of the mechanochemical abrasive is accelerated in a high-temperature strong alkali atmosphere.

  As described above, the composite abrasive grains of the present invention locally form a high-temperature, strong alkali atmosphere by a frictional heat reactant due to frictional heat generated with the material to be polished. A minute region around the portion where the material to be polished and the composite abrasive grain are in contact with each other becomes a high temperature strong alkali atmosphere. The 2nd abrasive | polishing agent integrated with the composite abrasive grain carries out a mechanochemical reaction actively in this atmosphere, and changes the polishing surface of a to-be-polished material. The first abrasive grinds a portion of the material to be polished that has deteriorated and has low hardness. Since this series of processing proceeds continuously in a short time by the integrated composite abrasive grains, a high polishing rate can be realized.

It is speculated that the same reaction occurs with SrCO ₃ , MgCO ₃ , BaCO _{3 and the} like. Since it is local that the frictional heat reactive agent forms a high-temperature strong alkali atmosphere, there is no effect of promoting the mechanochemical reaction unless the second abrasive is at a close distance. Therefore, even if the second abrasive and the frictional heat reactive agent are contained in the slurry in a separated state, the polishing rate as in this embodiment cannot be obtained. If the first abrasive is dispersed separately from the second abrasive in the slurry, the probability that the first abrasive will collide with the polished surface of the material to be polished which has been changed in quality is lowered. In the present invention, since the first abrasive is integrated into the composite abrasive, the altered surface of the material to be polished is reliably ground. As a result of the above, the composite abrasive grain of the present invention was able to obtain a high-quality polished surface by polishing the material to be polished at a sufficient polishing rate by wet polishing.

FIG. 8 is a table showing the relationship between the temperature of the slurry after polishing and the polishing rate.
Experimental Examples 1 to 8 are experiments in which composite abrasive grains using Al ₂ O ₃ as the first abrasive and SiO ₂ as the second abrasive and using different frictional heat reactants are used. It is a result. Each of these composite abrasive grains comprises 50% by weight of the first abrasive, 37.5% by weight of the second abrasive, and 12.5% by weight of the frictional heat reactive agent. Has been. The polishing conditions are all the same. The material to be polished is one having a surface roughness Ra−0.22 μm after the sapphire wafer is polished with GC (green carbonite) having an average particle size # 325. The temperature of the slurry before polishing was 25 degrees Celsius. The temperature of the slurry after polishing sapphire for 1 hour was measured. The polishing rate is obtained by measuring the thickness of the polished material after polishing and calculating the polishing amount per minute (min).

ref1 is a comparative example using abrasive grains that do not use a frictional heat reactant. ref2 is a comparative example in which only the frictional heat reactant (CaCO ₃ ) and the second abrasive SiO ₂ are used. ref3 is a comparative example using only the frictional heat reactive agent (CaCO ₃ ) and the first abrasive Al ₂ O ₃ .

  From the results of Experimental Examples 1 to 8, the temperature of the slurry after polishing was 30 degrees Celsius or higher. This means that the slurry was heated not only by heat generated by friction between the material to be polished and the abrasive but also by a chemical reaction of the frictional heat reactant. It can also be seen that the higher the temperature of the slurry after polishing, the higher the polishing rate. That is, it has been found that the more the chemical reaction of the frictional heat agent is caused by frictional heat, the faster the polishing rate becomes.

In the case of ref1, the polishing rate was 0.40 μm / min, and the temperature of the slurry after polishing was 27 degrees Celsius. Further, it was found that in ref2 (without the first abrasive) and ref3 (without the second abrasive), the slurry was heated to 41 degrees Celsius due to the heat generated by the frictional heat reactant. However, the polishing rate is not so high. Thus, it was proved that only the composite abrasive grains of the present invention combining the first abrasive, the second abrasive, and the frictional heat reactant sufficiently increase the polishing rate .

FIG. 9 is data showing the relationship between the polishing pressure and the polishing rate of Samples 1 to 3.
This example is for confirming the change in the polishing rate due to the change in the polishing pressure. In this figure, the holding device 24 presses the workpiece 26 in the direction of the polishing platen 20 with three polishing pressures of 160 g per square centimeter (g / cm ² ), 300 g / cm ² , and 500 g / cm ² . Experimental results are shown. Other operating conditions of the polishing apparatus are the same as in the embodiment of FIG.

According to this result, when the polishing pressure is increased, the polishing rate is improved. When the polishing pressure is 160 g / cm ² , the polishing rate is 1 micrometer per minute (μm / min), whereas when the polishing pressure is 500 g / cm ² , the polishing rate is 3.05 μm / min. The result of min was obtained. The polishing rate has tripled. Moreover, even when the polishing pressure was 500 g / cm ² , the surface roughness after polishing of the sapphire substrate could be 0.003 μm without any polishing scratches.

By increasing the polishing pressure, more frictional heat was generated, and at the same time, it was proved by this example that the composite abrasive grains efficiently scraped the polished surface of the material to be polished. Any of the composite abrasive grains of Samples 1 to 3 can polish the material to be polished at a higher speed than any conventional method .

  The composite abrasive grain of the present invention is used in a polishing process of a material to be used for a light emitting diode (LED) element substrate, other electronic component materials, power semiconductors, optical components, watches, electrically insulating materials, window materials, etc. Can be widely used. Compared to conventional polishing methods, the polishing time can be greatly shortened, and the cost of the product can be greatly reduced.

DESCRIPTION OF SYMBOLS 10 Composite abrasive grain 12 1st abrasive | polishing material 13 2nd abrasive | polishing agent 14 Friction heat reaction agent 16 A abrasive | polishing material 18 B abrasive | polishing material 17 Slurry 19 Polymer material 20 Polishing surface plate 22 Polishing pad 24 Holding device 25 Temperature control device 26 Material to be polished 28 Liquid injector 29 Light irradiation device 30 Arrow 32 Arrow 33 Arrow 34 Through-hole

Claims (14)

Abrasive grains for wet polishing sapphire,
A particulate first abrasive having a Mohs hardness of 7 to 9,
A particulate second abrasive having a mechanochemical action on the material to be polished;
A mixture of particulate frictional heat reactants, which is sparingly soluble in pure water used for the slurry and made of an alkali metal salt or an alkaline earth metal salt,
It is directly bonded by mechanical alloy method and integrated into particles,
The frictional heat reactant _is selected from _{CaCO 3, SrCO 3, MgCO 3} , BaCO 3, Li 2 CO 3, Ca 3 (PO 4) 2, Li 3 PO 4 and AlK (SO _{4) 2} groups In addition, a composite abrasive comprising one or two or more materials and occupying 5 to 95 weight percent of the integrated particles. _2. The composite abrasive according to claim 1, wherein the first abrasive is Al ₂ O ₃ , ZrSiO _4, or ZrO ₂ and occupies 5 to 95 weight percent of the integrated particles. The second abrasive is one or more materials selected from the group consisting of Cr ₂ O ₃ , Fe ₂ O ₃ and SiO ₂ , and is 5 weight percent of the integrated particles. The composite abrasive grain according to claim 1 occupying 95 weight percent or less. The composite abrasive grain according to claim 1, wherein when SiO ₂ is selected as the second abrasive, one having a Mohs hardness greater than SiO ₂ is selected as the first abrasive. Abrasive grains for wet polishing sapphire,
A particulate first abrasive having a Mohs hardness of 7 to 9,
A particulate second abrasive having a mechanochemical action on the material to be polished;
A mixture of particulate frictional heat reactants, which is sparingly soluble in pure water used for the slurry and made of an alkali metal salt or an alkaline earth metal salt,
It is directly bonded by mechanical alloy method and integrated into particles,
The first abrasive is Al ₂ O ₃ , ZrSiO ₄ or ZrO ₂ ,
The second abrasive is one or more materials selected from the group consisting of Cr ₂ O ₃ , Fe ₂ O ₃ and SiO ₂ ,
The frictional heat reactant is selected from the group of CaCO ₃ , SrCO ₃ , MgCO ₃ , BaCO ₃ , Li ₂ CO ₃ , Ca ₃ (PO ₄ ) ₂ , Li ₃ PO ₄ and AlK (SO ₄ ) _2. Further, composite abrasive grains that are one kind or two or more kinds of materials. The first abrasive, the second abrasive, and the frictional heat reactive agent according to claim 1 or 5 are combined by a mechanical alloy method so as to be integrated into particles having an average particle size of 0.05 μm to 100 μm. Composite abrasive. The first abrasive, the second abrasive, and the frictional heat reactive agent according to claim 1 or 5 are combined by a mechanical alloy method to be integrated into particles having an average particle size of 0.05 μm to 100 μm. A method for producing composite abrasive grains. A polishing method in which the material to be polished is wet-polished using a slurry in which the composite abrasive grains according to claim 1 or 5 are dispersed in pure water. The composite according to claim 1 or 5 , wherein when the composite abrasive grains are dispersed at a concentration of 15 weight percent in 100 ml of pure water to form a slurry, the pH at 25 degrees Celsius is 5 or more and 9 or less. A polishing method in which sapphire is wet-polished by selecting an abrasive composition. A slurry for wet polishing sapphire, wherein the apparent specific volume (stationary method) of the composite abrasive grain according to claim 1 or 5 is from 0.5 ml / g to 200 ml / g. An apparatus for supplying the slurry according to any one of claims 8 to 10 on a pad composed of any one of synthetic fiber, glass fiber, natural fiber, synthetic resin, and natural resin, and an elastic material to the pad A polishing apparatus comprising a pressing device that generates friction between the composite abrasive grains dispersed on the upper surface of the pad and the material to be polished. The composite abrasive grain according to claim 1 or 5 is dispersed and fixed on a pad made of any one of synthetic fiber, glass fiber, natural fiber, synthetic resin, and natural resin, and pure water is placed on the pad. And a pressing device that presses the material to be polished against the pad with elasticity to generate friction between the composite abrasive grains dispersed on the upper surface of the pad and the material to be polished. apparatus. The polishing apparatus according to claim 11 or 12 , further comprising a temperature control device for adjusting the temperature of the polishing slurry. The polishing apparatus according to claim 11, comprising means for irradiating the composite abrasive with light.

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