JP6373069B2 - Precision abrasive composition - Google Patents

Description

  The present invention is used in precision polishing processing using hard brittle materials such as lithium tantalate single crystal materials and lithium niobate single crystal materials as objects to be polished, and prevents the objects to be polished from causing frictional noise due to micro vibrations. The present invention relates to a precision abrasive composition.

  Conventionally, surface acoustic wave devices using surface acoustic waves (SAW) generated by the piezoelectric effect of piezoelectric materials have been widely used as electronic components such as intermediate frequency filters and resonators of televisions. In recent years, cellular phones in which such surface acoustic wave devices are used are remarkably expanded, and accordingly, the demand for piezoelectric wafers constituting the surface acoustic wave devices is also increasing.

  As such a piezoelectric wafer material, hard and brittle materials such as a lithium tantalate single crystal material and a lithium niobate single crystal material excellent in piezoelectricity and electro-optic effect are widely adopted. In the surface acoustic wave device wafer made of such a hard and brittle material, the surface on which the electrode is photo-printed is usually subjected to precision polishing, and the surface is made a mirror surface. Specifically, a surface plate on which a polishing cloth made of polyurethane or the like is attached is used, and the surface plate is rotated and a slurry as a polishing material is supplied onto the surface of the polishing cloth while a piezoelectric body as an object to be polished. The wafer material is pressed against the polishing cloth, and the surface of the piezoelectric wafer material is precisely polished.

  Oxide single crystals such as lithium tantalate and lithium niobate have a high hardness (Mohs's hardness of 5 to 6) and are also extremely chemically stable, so the polishing rate is very slow. Polishing of this oxide single crystal is usually carried out by a circulating supply system in which the polishing liquid is repeatedly supplied and recovered industrially. However, in order to obtain a desired thickness, polishing for a long time is required, and its production Inefficiency and efficiency are issues.

  When an oxide single crystal such as lithium tantalate single crystal or lithium niobate single crystal is precisely polished as an object to be polished, it is thought to be due to the characteristics of this material as a piezoelectric material. It is easy to cause a minute vibration called. As a result, there is a problem that the object to be polished is detached from the polishing position and cracked. It is also an important issue to suppress such fine vibration during polishing.

  An abrasive containing, as a main component, colloidal silica, which is used as a precision abrasive for silicon wafers, has been employed for polishing oxide single crystals such as lithium tantalate and lithium niobate. Such a colloidal silica abrasive has a feature that the accuracy of the polished surface can be achieved to a high degree without causing defects on the surface and the inner surface. On the other hand, depending on the polishing conditions and the like, an object to be polished called carrier squeal is used. Micro vibration occurs.

In addition, for the purpose of improving the polishing rate of lithium tantalate, lithium niobate, etc., Patent Document 1 discloses that the BET specific surface area is 10 to 60 m ² / g as a precision abrasive for hard and brittle materials, There has been proposed an aqueous slurry dispersion containing, as a solid component, only precipitated fine particle silica having an average particle size of 0.5 to 5 μm. Similarly, Patent Document 2 proposes that the polishing rate is improved by adding an additive such as sodium gluconate as an abrasive for hard and brittle materials, for the purpose of improving the dispersion stability of colloidal silica. Yes.

  Further, Patent Document 3 is known as an abrasive for a substrate of a lithium tantalate single crystal material or a lithium niobate single crystal material.

Japanese Patent Laid-Open No. 5-1279 JP 2006-150482 A JP 2002-184726 A

  However, the abrasives of Patent Documents 1 and 2 are not improved with respect to fine vibration called carrier squeal in polishing of piezoelectric materials.

  On the other hand, Patent Document 3 is an abrasive for a hard and brittle material substrate, but has a high polishing rate and aims to polish the appearance well. Therefore, it contains γ-alumina and silica, and further contains a lot of lubricants and dispersion aids. If alumina is included, the surface quality of the polished surface is limited, and if alumina and silica are included, sedimentation is likely to occur, which is unsuitable for circulating supply type polishing. Moreover, when a lot of lubricants and dispersion aids are contained, the viscosity increases and problems are likely to occur. Furthermore, Patent Document 3 does not consider carrier noise.

  Accordingly, there is a need for a solution to the problem that the object to be polished is liable to cause fine vibration during the precision polishing of lithium tantalate single crystal or lithium niobate single crystal, which is an obstacle to stable polishing.

  An object of the present invention is to provide a precision abrasive composition that suppresses fine vibration called carrier squealing of an object to be polished in precision polishing of an oxide single crystal substrate such as lithium tantalate or lithium niobate. .

  As a result of diligent studies to solve the above-mentioned problems, the present inventor has used a precision abrasive composition containing water, colloidal silica, and a water-soluble polymer compound, whereby a lithium tantalate / lithium niobate single crystal It has been found that fine vibrations of the object to be polished, called carrier squeal when polishing the material as the object to be polished, can be suppressed.

[1] water, and it contains an average particle size of 10~100nm colloidal silica, and a water-soluble polymer compound contains no alumina, the water-soluble polymer compound is a polysaccharide acids, lithium tantalate single crystal material Alternatively, a precision abrasive composition for precision polishing a lithium niobate single crystal material.

[2] The precision abrasive composition according to [1], wherein the concentration of the colloidal silica is 5 to 50% by mass.

[3] The polysaccharide, alginic acid, alginates, pectic acid, agar, xanthan gum, precision polishing agent composition according to the at least one selected from chitosan emissions by Li Cheng group [1] or [2] object.

[ 4 ] The precision abrasive composition according to any one of [1] to [ 3 ], wherein the content of the water-soluble polymer compound is 0.0001 to 1.0 mass%.

[ 5 ] The precision abrasive composition according to any one of [1] to [ 4 ], further containing a chelating compound.

[ 6 ] The precision abrasive composition according to any one of [1] to [ 5 ], wherein the pH of the precision abrasive composition is 7 to 11.

  Carrier which has been a problem when precision polishing a lithium tantalate single crystal material or a lithium niobate single crystal material by containing water, colloidal silica having an average particle diameter of 10 to 100 nm, and a water-soluble polymer The squeal can be suppressed. Thereby, improvement of polishing efficiency can be expected.

  Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

  The precision abrasive composition of the present invention contains water, colloidal silica having an average particle diameter of 10 to 100 nm, and a water-soluble polymer compound, and precisely polishes a lithium tantalate single crystal material or a lithium niobate single crystal material. Can be used to By defining the range of the average particle diameter of colloidal silica as 10 to 100 nm and including a water-soluble polymer compound, carrier noise can be prevented without lowering the polishing rate.

  In the present invention, colloidal silica refers to a stable colloidal dispersion of amorphous silica in a liquid. In this liquid, the average particle diameter of the silica particles is 10 to 100 nm, preferably 20 to 80 nm, and particularly preferably 30 to 70 nm. By setting the average particle size to 10 nm or more, carrier noise can be suppressed during polishing. By setting the average particle size to 100 nm or less, the polishing rate can be improved.

  The concentration of colloidal silica in the precision abrasive composition is preferably 5 to 50 mass%, more preferably 10 to 50 mass%, more preferably 20 to 40 mass%, from the viewpoint of ensuring a stable dispersion state of the abrasive particles and economic efficiency. Is more preferable. By setting it as 5 mass% or more, the polishing effect by colloidal silica, especially the outstanding surface quality can be obtained. On the other hand, when it is 50% by mass or less, not only is it advantageous in terms of economy, but also aggregation and gelation are unlikely to occur when further blending abrasives and other compounding agents other than colloidal silica. .

  Examples of the water-soluble polymer compound useful in the present invention include polysaccharides, polycarboxylic acids and esters thereof, and polyalkylene glycols.

  Examples of the polysaccharide include alginic acid, alginic acid ester, pectic acid, carboxymethylcellulose, agar, xanthan gum, chitosan, methylcellulose, ethylcellulose, hydroxypropylcellulose, hydroxyethylcellulose and the like.

  Examples of the polycarboxylic acid include polyaspartic acid, polyglutamic acid, polymethacrylic acid, polymaleic acid, and polyacrylic acid.

  Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and ethylene glycol-propylene glycol block copolymer.

  Of the water-soluble polymer compounds, the use of polysaccharides is preferred. Among the polysaccharides, it is more preferable to use at least one of alginic acid, alginic acid ester, pectic acid, carboxymethylcellulose, agar, xanthan gum, chitosan, methylcellulose, ethylcellulose, hydroxypropylcellulose, and hydroxyethylcellulose. In addition, the said water-soluble polymer compound can be used individually or in combination of 2 or more types.

  It is considered that the water-soluble polymer compound is easily adsorbed on the substrate surface such as lithium tantalate and lithium niobate. By adsorbing the water-soluble polymer compound to the surface of the substrate, unnecessary friction generated between the substrate and the abrasive grains or the polishing pad can be suppressed. By suppressing the friction more than necessary, it is considered that the polishing can be performed smoothly and the fine vibration of the object to be polished, called carrier noise, can be suppressed. In particular, since polysaccharides have an appropriate three-dimensional bulkiness when adsorbed on the substrate surface, it is considered that the effect of suppressing friction is higher and carrier noise can be further suppressed.

  The content of the water-soluble polymer compound is 0.0001 to 1.0% by mass, preferably 0.001 to 0.5% by mass, more preferably 0.003 to 0.3% by mass, -0.1 mass% is especially preferable. By making the content of the water-soluble polymer compound 0.0001% by mass or more, the effect of suppressing carrier noise during polishing can be made sufficient. Moreover, by setting it as 1.0 mass% or less, it can prevent that a viscosity increases and fluidity | liquidity falls, and workability | operativity can be improved.

  The precision abrasive composition of the present invention preferably further contains a chelating compound from the viewpoint of improving the polishing rate. Examples of the chelating compound include polyaminocarboxylic acid compounds, polyamine compounds, phosphonic acid compounds, polyhydric alcohol compounds, and the like.

  Examples of polyaminocarboxylic acid compounds include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, nitrilotriacetic acid, and the like, and ammonium salts, amine salts, sodium salts, potassium salts, and the like.

  Examples of the polyamine compound include monomers such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine, and salts of these hydrochlorides.

  Examples of phosphonic acid compounds include diethylenetriaminepentamethylenephosphonic acid, phosphonohydroxyacetic acid, hydroxyethyldimethylenephosphonic acid, aminotrismethylenephosphonic acid, hydroxyethanephosphonic acid, ethylenediaminetetramethylenephosphonic acid, hexamethylenediaminetetramethylenephosphonic acid, etc. And their ammonium salts, amine salts, sodium salts, potassium salts and the like.

  Examples of the polyhydric alcohol compound include ethylene glycol, propylene glycol, gluconic acid, sodium gluconate, and potassium gluconate.

  Among the chelating compounds, the use of polyaminocarboxylic acid compounds, polyamine compounds, and phosphonic acid compounds is preferable.

  The content of the chelating compound in the precision abrasive composition is preferably 0.05 to 4% by mass, more preferably 0.1 to 3% by mass, and still more preferably 0.2 to 2% by mass. By setting it to 0.05% by mass or more, the polishing rate can be further improved. By setting the content to 4% by mass or less, carrier noise can be prevented from occurring during polishing.

  Moreover, it is preferable that pH of the precision abrasive | polishing agent composition of this invention is adjusted to 7-11 alkalinity. When the pH is 7 to 11, the charge of the colloidal silica particles tends to increase negatively. As a result, the electric repulsive force acting between the particles is increased, effectively acting on each particle, and the abrasive particles are evenly dispersed.

  On the other hand, when the pH is less than 7, particularly when the pH is in the vicinity of 5 to 6, the balance of charge between the particles is lost, and the particles are likely to aggregate and gel. Further, when the pH exceeds 11, the silica surface gradually dissolves and it becomes difficult to effectively exhibit the function as a precision abrasive composition.

  By the way, when manufacturing the precision abrasive | polishing agent composition for the lithium tantalate single crystal / lithium niobate single crystal material made into the objective of this invention, the following method can be illustrated. In addition, the preparation method of the precision abrasive | polishing agent composition for the lithium tantalate single crystal / lithium niobate single crystal material by this invention is not limited to an illustrated method, It is to the abrasive | polishing material, additive, etc. which are mix | blended Depending on the situation, it can be implemented in various ways.

  A water-soluble polymer compound is added to an aqueous solution prepared in advance at a predetermined pH (alkaline), mixed and stirred to obtain a uniform solution, and then added to colloidal silica, followed by mixing and stirring. A precision abrasive composition is obtained.

  Then, when performing precise polishing on a lithium tantalate or lithium niobate single crystal material using the precision abrasive composition of the present invention, various conventionally known polishing techniques can be appropriately selected. . For example, a predetermined amount of precision abrasive composition is put into a supply container provided in a polishing machine. Using a nozzle or tube from the supply container, the precision abrasive composition is dropped and supplied to a polishing cloth made of polyurethane or the like affixed on the surface plate of the polishing machine, while the polishing surface of the object to be polished is polished. The surface of the material to be polished is precisely polished by pressing against the cloth surface and rotating the surface plate at a predetermined rotation speed.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples. In addition to the following examples, various changes and modifications can be made to the present invention based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

(Preparation of precision abrasive composition)
The precision abrasive compositions of Examples 1 to 12 and Comparative Examples 1 to 6 were prepared by the method shown below so that the blending ratios shown in Table 1 or Table 2 were obtained.

Example 1
To 800 g of commercially available alkaline colloidal silica (average particle size 40 nm, solid content 50 mass%, pH = 11), 0.3 g of xanthan gum was added. Furthermore, 200 g of an acidic aqueous solution prepared by adding malonic acid to the pH shown in Table 1 was added and stirred to obtain 1 kg of a uniform precision abrasive composition.

(Example 2 and Example 12)
8 g of ethylenediaminetetraacetic acid disodium salt (EDTA.2Na) and 0.3 g of xanthan gum were added to 800 g of commercially available alkaline colloidal silica (average particle size 40 nm, solid content 50 mass%, pH = 11). Further, 200 g of an alkaline aqueous solution prepared by adding a 5% aqueous potassium hydroxide solution to the pH in Tables 1 and 2 was added and stirred to obtain 1 kg of a uniform precision abrasive composition.

(Examples 3 to 7)
By changing the blending ratio of each component of Example 2, 1 kg of each of the precision abrasive compositions of Examples 3 to 7 was obtained.

(Examples 8 to 9)
The ethylenediaminetetraacetic acid disodium salt of Example 2 was changed to Phosphonobutanetricarboxylic acid (PBTC) in Example 8, and Example 9 was changed to ethylenediaminetetraacetic acid dicalcium salt (EDTA · 2Ca). 1 kg of each precision abrasive composition was obtained.

(Examples 10 to 11)
The xanthan gum of Example 1 was changed to propylene glycol alginate as a water-soluble polymer in Example 10, hydroxypropylcellulose as a water-soluble polymer in Example 11, and the precision abrasive composition of Examples 10-11. 1 kg of each product was obtained.

(Comparative Example 1)
By adding 200 g of an acidic aqueous solution prepared by adding malonic acid to the pH in Table 1 to 800 g of commercially available alkaline colloidal silica (average particle size 40 nm, solid content 50 mass%, pH = 11), and stirring, 1 kg of a uniform precision abrasive composition was obtained. Comparative Example 1 does not contain a water-soluble polymer.

(Comparative Example 2 and Comparative Example 6)
8 g of EDTA · 2Na was added to 800 g of commercially available alkaline colloidal silica (average particle size 40 nm, solid content 50 mass%, pH = 11). Further, 200 g of an alkaline aqueous solution prepared by adding a 5% aqueous potassium hydroxide solution to the pH shown in Tables 1 and 2 was added and stirred to obtain 1 kg of a uniform precision abrasive composition. Comparative Example 2 and Comparative Example 6 do not contain a water-soluble polymer.

(Comparative Examples 3-4)
By changing the average particle size of the colloidal silica of Example 2, 1 kg of each of the precision abrasive compositions of Comparative Examples 3 to 4 was obtained.

(Comparative Example 5)
Instead of the xanthan gum of Example 1, sodium gluconate was used and the blending ratio was changed to obtain 1 kg of the precision abrasive composition of Comparative Example 5, respectively.

(Polishing test)
Each of the 1 kg precision abrasive compositions of Examples 1 to 12 and Comparative Examples 1 to 6 obtained above was double-side polished (SPEED FAM, manufactured by 6B-5P-II, polishing platen diameter: 422 mm). Then, using this polishing machine, a substrate made of a lithium tantalate single crystal material or a lithium niobate single crystal material (diameter: 76 mm, thickness: 0.3 mm) is used. The surface was polished for 5 hours.

During polishing, the rotation speed (rotation speed) of the surface plate was set to 55 rpm, and the polishing pressure was 300 g / cm ² . The precision abrasive composition is supplied onto the polishing cloth affixed on the surface plate at a supply rate of 200 ml / min using a tube pump, and the overflowing precision abrasive composition is returned to the container. It was used repeatedly by the so-called circulation supply system. Then, while polishing the surface of the substrate as described above, the thickness of the substrate is measured using a micrometer (Mitutoyo Corp., measurement accuracy: 1 μm) every time polishing time of 1 hour elapses. The polishing rate per hour (μm / hr) was determined. Table 1 shows the results of the lithium tantalate single crystal substrate, and Table 2 shows the results of the lithium niobate single crystal substrate. In Comparative Example 3, since the carrier squeal was intense, polishing was stopped halfway.

(Determination of carrier noise)
From immediately after the start of polishing to the end of polishing, the sound generated from the periphery of the rotating platen (carrier) of the polishing tester was evaluated according to the following to determine whether carrier squeak occurred.
○: Normal sliding sound during polishing is recognized.
X: A frictional sound, not a sliding sound, is recognized.
Xx: A strong frictional sound is recognized.

  The effect of this invention is clear from the result of Tables 1-2. From the comparison of Examples 1, 10, 11 and Comparative Example 1, the comparison of Examples 2, 3, 4 and Comparative Example 2, the comparison of Example 12 and Comparative Example 6, etc. It can be seen that carrier noise is suppressed while maintaining the polishing rate. From the comparison between Example 2 and Comparative Example 3, it can be seen that if the particle size of the colloidal silica is too small, carrier squeal becomes intense and hinders polishing. From the comparison between Example 2 and Comparative Example 4, it can be seen that the polishing rate decreases when the particle size of the colloidal silica is too large. From the comparison between Comparative Example 1 and Comparative Example 5, it can be seen that the addition of sodium gluconate shown in Patent Document 2 does not improve carrier noise. That is, when the water-soluble polymer is not included and sodium gluconate as a chelating compound is included, carrier squealing is not improved. From the comparison of Examples 2, 7, 8, 9 and Example 1, addition of a water-soluble polymer and further addition of a chelating compound can provide an effect of improving the polishing rate in addition to suppressing carrier noise. Recognize.

  As described above, carrier noise can be suppressed while maintaining the polishing rate by adding a water-soluble polymer. Further, when a chelating compound is added, the polishing rate can be improved while suppressing carrier noise.

  The precision abrasive composition of the present invention can be used for precision polishing of lithium tantalate single crystal materials and lithium niobate single crystal materials.

Claims (6)

Containing water, colloidal silica having an average particle diameter of 10 to 100 nm, and a water-soluble polymer compound;
Does not contain alumina,
The water-soluble polymer compound is a polysaccharide acids,
A precision abrasive composition for precision polishing a lithium tantalate single crystal material or a lithium niobate single crystal material.   The precision abrasive | polishing agent composition of Claim 1 whose density | concentration of the said colloidal silica is 5-50 mass%. Wherein the polysaccharide is alginic acid, alginates, pectic acid, agar, xanthan gum, fine polishing composition according to claim 1 or 2 is at least one selected from chitosan emissions by Li Cheng group.   The precision abrasive | polishing agent composition of any one of Claims 1-3 whose content of the said water-soluble polymer compound is 0.0001-1.0 mass%.   Furthermore, the precision abrasive | polishing agent composition of any one of Claims 1-4 containing a chelating compound.   The precision abrasive composition according to any one of claims 1 to 5, wherein the precision abrasive composition has a pH of 7 to 11.