JP2007321159A - Precisely abrasive composition for hard and brittle material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precisely abrasive composition for a hard and brittle material, used for the precise polishing of the hard and brittle material, capable of polishing the surface of the hard and brittle material with high precision, and capable of achieving excellent polishing speed and polishing life. <P>SOLUTION: The precisely abrasive composition for the hard and brittle material is constituted by dispersing or dissolving a colloidal silica having grain size different from that of a base abrasive, and a chelate compound as a polishing promoter in the colloidal silica as the base abrasive. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a precision polishing composition for hard and brittle materials, and in particular, when polishing hard and brittle materials such as lithium tantalate single crystal materials and lithium niobate single crystal materials, provides a precise and clean surface quality. The present invention relates to a precision polishing composition for hard and brittle materials having excellent polishing efficiency and polishing life.

  2. Description of the Related Art Conventionally, surface acoustic wave devices using surface acoustic waves (SAW) generated by piezoelectric effects in piezoelectric bodies have been widely used as electronic components such as television intermediate frequency filters and resonators, especially in recent years. However, the penetration rate of mobile phones using such surface acoustic wave devices has been remarkably increased, and along with this, the demand for piezoelectric wafers constituting such surface acoustic wave devices has also increased exponentially. It is increasing. As such piezoelectric wafer materials, hard and brittle materials such as lithium tantalate single crystal materials and lithium niobate single crystal materials having excellent piezoelectricity, pyroelectricity, and electro-optic effect are widely used. is there.

  In a 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 into a mirror surface. Specifically, using a surface plate with an abrasive cloth made of polyurethane or the like, while rotating the surface plate, supplying slurry-like abrasive onto the surface of the abrasive cloth, By pressing the wafer against the polishing cloth surface, the wafer surface is precisely polished (polished), so that the precision polishing is performed.

  In addition, the polishing material used in this precision polishing process is excellent in polishing efficiency or polishing rate, as well as being capable of finishing the surface of the material to be processed (wafer) to a highly precise polishing finish. That is desired. Moreover, such an abrasive is generally used repeatedly by circulating a certain amount thereof for economic reasons (so-called circulation supply system), and in such use, As the polishing efficiency decreases, it is necessary to replace a part of the abrasive material with a new abrasive material, or to replace all of the abrasive material with a new one after a predetermined polishing time. It is required that the efficiency (speed) can be maintained constant over a long period of time, in other words, the polishing life is good.

  By the way, in hard brittle materials such as lithium tantalate single crystal material used as the wafer material as described above, since it is hard and brittle, it is usually used for finish polishing as an abrasive, and the particles are coarse and hard. If a hard abrasive such as alumina or diamond is used, the polishing speed will increase, but pits and scratches will occur on the polishing surface, processing distortion will remain inside the wafer surface, and surface accuracy will be extremely poor. Since the problem is inherent, the practical application was extremely difficult, and since it is a chemically stable material, the polishing effect due to the mechanochemical action is extremely low. No useful polishing acceleration effect based on mechanochemical action has been reported, and no effective polishing accelerator has been found. That.

  Therefore, colloidal silica as disclosed in JP-A-58-225177, JP-A-62-233333, JP-A-5-154760 and the like is mainly used as a precision polishing material for such a wafer. Silicon wafer abrasives, which are included as components, have been adopted, but in such colloidal silica abrasives, the accuracy of the polished surface is achieved to a high degree without causing defects on the surface and the inner surface. However, it was difficult to say that the polishing rate (polishing efficiency) was sufficient, and it was a major obstacle to shortening the polishing time. Since this also causes a problem that the speed is remarkably reduced, as described above, when the circulating supply method is adopted, the abrasive is frequently replaced. Cormorants need is for it to have occurred. For this reason, such a method has problems such as deterioration in work efficiency and workability and an increase in cost required for abrasives and equipment.

And in order to cope with such a problem, as a surface precision abrasive for hard and brittle materials, Japanese Patent Laid-Open No. 5-1279 has a BET specific surface area of 10 to 60 m ² / g, An aqueous slurry dispersion containing only fine particulate silicon dioxide having an average particle size of 0.5 to 5 μm as a solid component has been proposed, in which the surface accuracy of the polished surface is maintained well and the above-mentioned Although the polishing life is improved as compared with colloidal silica abrasives, there is still room for improvement with respect to the polishing rate.

  JP-A-6-191988 discloses only a specific colloidal silica, that is, a colloidal silica in which a solid component (silica) having a particle size of 30 to 70 nm is dispersed in a basic aqueous solution having a pH of 9 to 14. However, it is only disclosed to prevent warping of the optical wafer after forming the epitaxial growth layer by making the polishing surface of the optical wafer a mirror surface. The polishing rate and the polishing life have not been studied.

JP 58-225177 A JP 62-30333 A Japanese Patent Laid-Open No. 5-154760 Japanese Patent Laid-Open No. 5-1279 JP-A-6-191988

  Here, the present invention has been made in the background of such circumstances, the problem to be solved is that in the precise polishing processing of the hard and brittle material, the hard and brittle material, pits, scratches, protrusions, Another object of the present invention is to provide a precision polishing composition for hard and brittle materials that can polish the surface with high accuracy without causing polishing defects such as processing distortion and can realize an excellent polishing rate and polishing life. .

  As a result of intensive studies to solve the above-described problems, the present inventors have found that colloidal silica having a particle diameter different from that of the base abrasive is compared with colloidal silica as the base abrasive that is the main component in the polishing composition. The present inventors have found that by adding a chelating compound together with silica, excellent polishing surface accuracy, polishing rate and polishing life can be realized.

  Accordingly, the present invention has been completed based on such knowledge, and one of the gist thereof is that the average particle size of the first colloidal silica is different from that of the first colloidal silica. The precision polishing composition for hard and brittle materials is characterized in that at least one of different second colloidal silicas is added and contained, and further, a chelating compound is added and contained as a polishing accelerator.

  Further, according to one of the preferred embodiments of the precision polishing composition for hard and brittle materials according to the present invention as described above, the first colloidal silica is contained in a solid content of 10 to 50% by weight. The first colloidal silica and the second colloidal silica are contained in a total amount of solids in a proportion of 20 to 60% by weight.

  Furthermore, according to another preferred embodiment of the present invention, the average particle size of the first colloidal silica is 30 to 60 nm, while the average particle size of the second colloidal silica is 5 to 22 nm or 80 to 100 nm. And the first colloidal silica and the second colloidal silica are used so that the ratio by weight of the solid content is 60 to 80% and 40 to 20%.

  In the polishing composition according to the present invention, as the polishing accelerator, at least one of a polyaminocarboxylic acid chelating compound and an organic phosphonic acid chelating compound is advantageously used.

  Moreover, it is desirable that the polishing accelerator added to the polishing composition according to the present invention is contained in a proportion of 0.1 to 5.0% by weight.

  Furthermore, in the present invention, in order to solve the above-described problems, at least one second colloidal silica having an average particle size different from that of the first colloidal silica is added to the first colloidal silica, Precise polishing for hard and brittle materials characterized by containing and dispersing and containing at least one of silica particles and alumina particles, and further adding and containing a chelating compound as a polishing accelerator. The gist is also the composition.

  Furthermore, in the precision polishing composition for hard and brittle materials according to the present invention, amorphous silicon dioxide and fumed silica are advantageously used as the silica particles, and fumed alumina is advantageously used as the alumina particles. Become.

  In addition, according to one of the preferable embodiments of the polishing composition according to the present invention, at least one of the silica particles and the alumina particles is contained in a total amount of 2 to 25% by weight. You will be harassed.

  In the precision polishing composition for hard and brittle materials according to the present invention as described above, it is desirable that the pH is adjusted to alkalinity of 7 to 11, and in the present invention, it is hard and brittle. Desirably, the material is a lithium tantalate single crystal material or a lithium niobate single crystal material.

  The precision polishing composition for hard and brittle materials according to the present invention has a great feature when combining a plurality of colloidal silicas having different average particle sizes and hence different particle size distributions. It is possible to achieve an effective improvement. That is, by combining such colloidal silicas having different particle sizes, the particle size distribution of the silica in the colloidal silica is made wide, so that an excellent surface quality is ensured without causing poor polishing. In addition, good functions can be realized in the polishing rate and its maintenance.

  Further, in the precision polishing composition for hard and brittle materials according to the present invention, a predetermined chelating compound is added as a polishing accelerator and has a great feature. In such a polishing composition according to the present invention, the polishing composition containing only a conventional colloidal silica and containing no polishing accelerator is provided, for example, by moderately reducing the polishing resistance during polishing. Compared to the above, the polishing rate can be further improved, and such a polishing rate can be maintained over a long period of time, and an excellent polishing life can be achieved.

  And, in such a precise polishing composition for hard and brittle materials, the above-mentioned effect by combining a plurality of colloidal silicas having different average particle sizes and a polishing promoting effect by a chelating compound are combined, thereby polishing processing. In this case, a more excellent polishing surface is obtained, and the polishing rate and its sustainability are advantageously improved.

  In addition, in the present invention, a chelating compound is added to and contained in the first and second colloidal silicas having different average particle sizes, and at least one of silica particles and alumina particles is further added. The precise polishing composition for hard and brittle materials, characterized by being dispersed and contained, is also the gist thereof. In such a precise polishing composition for hard and brittle materials, a base abrasive is used. From colloidal silica, which contains both predetermined silica particles and / or alumina particles that give excellent polishing characteristics, colloidal silica having a different average particle size from the base abrasive, and a chelating compound. Even better polishing characteristics can be achieved.

  In short, the precision polishing composition (abrasive) for hard and brittle materials according to the present invention is a silica sol that is a colloidal solution of silicic acid, particularly a silica sol whose dispersion state is stabilized by a special treatment. Colloidal silica is used as a base abrasive, while colloidal silica with different average particle size as another abrasive and chelating compound as a polishing accelerator are further dispersed or dissolved and blended. From a certain point, in the precision polishing processing of hard and brittle materials, while ensuring excellent surface properties, the polishing efficiency and the polishing life can be improved extremely effectively. Colloidal silica used as a base abrasive is a polishing material for hard and brittle materials, which is a polishing material among the above-mentioned various polishing characteristics. In order to maintain the surface quality of the surface highly, it is the essential ingredient.

  By the way, as such colloidal silica, any known particle size and content (solid content) of silica as a solid component in such colloidal silica can be adopted, but the polished surface is a very beautiful mirror surface. In order to finish, a particle diameter in the range of 5 to 150 nm is preferably employed, and as the solid content of colloidal silica, the stable dispersion state of the abrasive and its economic efficiency In consideration of the above, the content is preferably 10 to 50% by weight, and among those particle sizes and solid contents, those having a large particle diameter and a high solid content are advantageously used for obtaining a high polishing rate. Will be. When the colloidal silica particle size is smaller than 5 nm, an effective polishing rate cannot be obtained. When the particle size is larger than 150 nm, the surface quality is deteriorated and the cost is increased. It ends up. Further, when the solid content is less than 10% by weight, a polishing effect by colloidal silica, in particular, excellent surface quality cannot be obtained. When the solid content exceeds 50% by weight, only a rapid increase in cost is caused. In other words, when an abrasive other than colloidal silica as the base abrasive and other compounding agents are further blended, there arises a problem that aggregation and gelation easily occur.

  In the present invention, in addition to the colloidal silica (first colloidal silica) as the base abrasive as described above, another colloidal silica (second colloidal silica) having an average particle size different from that of the colloidal silica is used. By adding and containing at least one of the above, an effective precision polishing composition for hard and brittle materials is formed.

  That is, in the precision polishing composition for hard and brittle materials according to the present invention, the colloidal silica having different average particle sizes is combined, so that the particle size distribution of the solid content (silica) in the colloidal silica becomes wide. In the precision polishing processing of hard and brittle materials, the polishing surface is made to be a mirror surface without causing poor polishing, and an excellent polishing rate and polishing life can be obtained. Therefore, among the solid contents in colloidal silica having such a wide distribution range, those having a large average particle size increase the polishing rate, and those having a smaller average particle size improve the finished state of the polished surface. It is thought to work.

  And when combining two or more kinds of colloidal silicas having different average particle sizes, the solid content in those colloidal silicas should be appropriately determined in consideration of the required polishing characteristics and the like. However, the second colloidal silica is combined with the first colloidal silica and the second colloidal silica with respect to the first colloidal silica having a solid content of 10 to 50% by weight as the base abrasive. The total solid content is preferably 20 to 60% by weight, more preferably 20 to 50% by weight.

  When the solid content of the first colloidal silica and the second colloidal silica is less than 20% by weight, the effect of improving the polishing rate by combining a plurality of colloidal silicas as described above can be obtained. In addition, when it exceeds 60% by weight, not only is it uneconomical, but the dispersion state of silica in colloidal silica is destabilized, resulting in problems that uniform dispersion cannot be achieved. It becomes. In general, the maximum solid content of commercially available colloidal silica is about 50% by weight, but it is possible to produce colloidal silica with a solid content of 50% by weight or more by concentrating with a filtration membrane or filter. It is. However, since the partially stable colloidal silica structure is easily broken by concentration, it is desirable to make it 60% by weight or less in consideration of the above-mentioned problems such as non-uniform dispersion. By virtue of this, the silica in the colloidal silica can be dispersed in a single and uniform manner, so that problems such as aggregation and gelation due to the silica particles in the polishing composition can be prevented or prevented, and poor polishing such as pits and scratches In addition, a decrease in polishing accuracy can be avoided very effectively.

  By the way, as a combination of the above colloidal silica, practically, the first colloidal silica adopts an average particle size of 30 to 60 nm, and the second colloidal silica has an average particle size of 5 to 5 nm. It is desirable to adopt a film having a thickness of 22 nm and / or 80 to 100 nm, whereby the effects as described above are more effectively exhibited. In particular, when the second colloidal silica having an average particle size of 5 to 22 nm is adopted, the surface quality is further improved and the cost reduction is advantageously achieved. When a colloidal silica having an average particle size of 80 to 100 nm is employed, the polishing rate is effectively improved.

  Moreover, when mix | blending such colloidal silica of several average particle sizes, the 1st colloidal silica and the 2nd colloidal silica are 60-80% and 40-20%, respectively by the weight ratio of solid content. It is desirable to mix them in proportions, whereby the various effects described above can be improved more effectively. However, such a mixing ratio is an appropriate distribution range for close packing, and by adopting this range, the polishing speed and surface quality are advantageously improved, and good economic efficiency is realized. Because it can be done. In addition, when the blending ratio of the second colloidal silica is less than 20%, no effect of the blending is exhibited.

  And the polishing composition according to the present invention is the one in which a chelating compound is added as a polishing accelerator to the colloidal silica as described above, and dissolved and contained. In such a polishing composition, by adding a chelating compound, the polishing resistance at the time of polishing is moderately eased, etc., and the polishing rate is advantageously improved. It is maintained over a long period of time and an excellent polishing life is realized.

  Examples of such chelating compounds include polyaminocarboxylic acid chelating compounds and organic phosphonic acid chelating compounds, and at least one of them is appropriately selected and used. Is desirable. As such polyaminocarboxylic acid-based chelating compounds, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid, sodium salts, ammonium salts and calcium salts thereof are preferably employed, and organic phosphonic acid-based chelating properties are also used. As the compound, phosphonobutane tricarboxylic acid (PBTC), hydroxyethane diphosphonic acid, aminotrismethylene phosphonic acid and salts thereof are advantageously used.

  The chelating compound as described above is preferably added at a ratio of 0.1 to 5.0% by weight, more preferably a blending ratio of 0.5 to 3.0% by weight. Thus, even better polishing efficiency can be obtained. However, when the blending ratio is less than 0.1% by weight, the improvement of the polishing rate is not exhibited, and when it is more than 5.0% by weight, not only the cost is increased but also it is commensurate with it. This is because the above effect cannot be obtained.

  Further, in the present invention, two or more kinds of colloidal silica having different average particle sizes are blended, to which predetermined silica particles and / or alumina particles are dispersed, and further, a predetermined chelating compound as a polishing accelerator is added. The added precision polishing composition for hard and brittle materials can also be advantageously employed. In these precision polishing compositions for hard and brittle materials, predetermined silica particles and / or alumina particles, colloidal silica having an average particle size different from the base abrasive, and a chelating compound are colloidal as the base abrasive. By being blended with silica, it is possible to exhibit more excellent polishing properties or polishing effects than when one of them is blended with the base abrasive alone.

  That is, in one of the precision polishing compositions for hard and brittle materials according to the present invention, at least one of predetermined silica particles and alumina particles is appropriately selected with respect to the colloidal silica as described above. Because it is configured to be dispersed in a fine fine particle state, poor polishing such as pits, scratches and processing distortion is effectively avoided, and the surface of the hard and brittle material has a very beautiful mirror surface. In addition to being able to be precisely polished, the polishing rate can be advantageously improved, and the polishing time can be effectively shortened. An excellent polishing life that can be maintained over time could be realized. By improving the polishing speed and the polishing life, it is possible to improve work efficiency and workability in precision polishing and to achieve good economic efficiency.

  Such silica particles and alumina particles are required not to deteriorate the excellent surface properties due to colloidal silica as described above during precision polishing, and in particular, those in the form of extremely fine fine powders. It will be suitably adopted. Specifically, the silica particles include amorphous silicon dioxide and fumed silica, while the alumina particles include fumed alumina, and such fine silica particles and / or alumina particles are blended. It is possible to achieve an excellent polishing rate and polishing life by being caulked, because, according to the inventor's inference, such silica particles and alumina particles are more suitable than colloidal silica. This is considered to be due to the fact that it is hard. Although the hardness of such colloidal silica, silica particles, and alumina particles has not been measured, amorphous silicon dioxide and fumed silica have a net-like or chain-like shape in which spherical silica is in an aqueous solution. In contrast to colloidal silica, colloidal silica is presumed to be softer because spherical silica is monodispersed in a colloidal form, and in the case of fumed alumina, its material In addition, it is considered to be harder than colloidal silica.

Specifically, the amorphous silicon dioxide used in the present invention is a fine powdery amorphous silica produced by a wet method (a typical method is a method of neutralizing sodium silicate with an acid) ( Since the silica particles are manufactured in a gel state, the silica particles are not merely aggregated but fused, and the final dried product generally has certain secondary particles. It has become. Among amorphous silicon dioxide composed of such secondary particles, in order to increase the polishing rate and the polishing life while maintaining excellent surface properties, it is desirable to select a fine particle diameter, An average particle diameter of 1.0 to 5.0 μm and a BET specific surface area of 110 to 420 m ² / g are advantageously employed.

On the other hand, fumed silica used in the present invention is a silica (gas phase method silica) produced by a gas phase reaction method or a dry method among fine powdery amorphous silica, Since it is manufactured in this way, it is composed of primary particles having an extremely fine particle size close to that of an aerosol. Among these fumed silicas, in order to increase the polishing speed and the polishing life while maintaining excellent surface properties, it is desirable to select particles having a small specific surface area and large primary particles. The average particle size of: 12 to 40 nm and the BET specific surface area of 50 to ²⁰⁰ m ² / g are more preferably used. The above gas phase reaction method is a reaction (oxidation reaction) between a metal compound (silicon compound) vapor and a reactive gas. Specifically, silicon tetrachloride vapor is heated to 1000 ° C. or more with hydrogen and oxygen. Examples include a method in which hydrolysis is performed at a high temperature. In the present invention, fumed silica that has been subjected to special curing treatment by employing a technique such as mixing aluminum chloride at the time of vapor phase synthesis is also preferably used for obtaining a high polishing rate. It is.

Further, the fumed alumina used in the present invention is also alumina (gas phase method alumina) produced by a gas phase reaction method, similar to the fumed silica described above. It is made of extremely fine primary particles because it is produced in the gas phase by introducing water vapor or the like there. Among such fumed aluminas, in order to effectively improve the polishing rate and the polishing life, those having a small specific surface area and large primary particles are preferable. Those having an average particle diameter of 10 to 40 nm and a BET specific surface area of 40 to 100 m ² / g are more preferably used. And since such fumed alumina is composed of harder alumina than silica, it has a higher effect of improving the polishing rate than the above-mentioned amorphous silicon dioxide and fumed silica. Among them, since it is relatively soft and has an appropriate hardness, the surface of the material to be polished will not be damaged by causing damage such as pits and scratches.

  Such silica particles and / or alumina particles are preferably blended so that the total amount is 2 to 25% by weight, which enables uniform monodispersion of silica particles and / or alumina particles. Thus, the gelation of the polishing composition can be prevented, and various excellent effects such as an extremely beautiful polishing mirror surface can be obtained. When the blending ratio is less than 2% by weight, there is almost no effect by adding it. Conversely, when the blending ratio is more than 25% by weight, not only the cost increases, but the composition The overall dispersion state is deteriorated, specifically, aggregation and gelation are induced, and as a result, the surface properties of the polished surface are deteriorated. In particular, when fumed alumina is employed, the polishing rate is advantageously improved even with a small amount of the compound, and conversely, when the compounding amount is increased, the viscosity of the composition is remarkably increased. It is.

  Moreover, in the precision polishing composition for hard and brittle materials according to the present invention, it is desirable that the pH value is adjusted to be alkaline of 7 to 11, whereby the electric repulsive force working between the particles is Effectively acting on each particle, the solid component will be evenly dispersed. In other words, the viscosity of the precision polishing composition for hard and brittle materials is reduced, and as much as possible. From the point where uniform dispersion can be achieved, it is advantageously suppressed or caused that the fine particles aggregate and solidify to cause problems such as a decrease in polishing accuracy and difficulty in circulation utilization. It can be prevented, and the content of silica in the polishing composition can be increased. However, when the pH is less than 7, particularly when the pH is around 5 to 6, the charge balance between the particles is lost, the particles are joined together, and thickening, gelation, and aggregation of the fine particles are caused. Therefore, it becomes impossible to disperse evenly, so that the polishing accuracy is lowered and repeated use becomes difficult. On the other hand, when the pH exceeds about 11, the silica surface gradually dissolves and polishes. The function as a composition cannot be exhibited effectively.

  For example, in the case of fumed silica having a very fine particle size, it is easy to be bulky due to its fineness, and thus easily causes thickening and gelation. Therefore, it is particularly affected by pH. It is easy. Specifically, the isoelectric point of fumed silica is in the vicinity of pH = 2, pH = 4-5 is a dispersion region, pH = 7-8 is a thickening region, and pH = 9-10 is a dispersion region. As can be seen from this, when fumed silica is simply dispersed in water (pH = about 7), the viscosity increases, and when stirred, the viscosity sometimes increases rapidly in a gel state. The method of dispersing in a solution adjusted to the above is advantageously used.

  Further, for such pH adjustment, various pH adjusting agents are appropriately selected according to the abrasive and the compounding agent to be blended in the polishing composition, and are used so as to obtain a desired pH. Examples of such a pH adjuster include NaOH, KOH, ammonia and the like.

  Furthermore, in the precision polishing composition for hard and brittle materials according to the present invention, if necessary, a conventionally known dispersant, for example, in order to further disperse the solid component and further promote the polishing, Add organic amines, anionic and nonionic surfactants, and etchants used for surface processing of other metal materials, such as aluminum salts such as aluminum nitrate, ferrous chloride, etc. An organic acid such as iron salt and citric acid may be added, and, in addition, other conventionally known various additives added to the polishing composition may also be used as long as they do not inhibit the above-described effects. It may be appropriately selected and added in an appropriate amount.

  The precision polishing composition according to the present invention is to be used for precision polishing of various hard and brittle materials. Among such hard and brittle materials, in particular, lithium tantalate single crystal material or niobic acid The present invention can be advantageously applied to a lithium single crystal material, whereby various excellent effects as described above can be effectively exhibited.

  By the way, when manufacturing the precise polishing composition for hard and brittle materials which is the object of the present invention, the following methods can be exemplified. In addition, the preparation method of the polishing composition for hard and brittle materials according to the present invention is not limited to the exemplified method, and is nevertheless carried out in various modes depending on the abrasives and additives to be blended. obtain.

Mixing of colloidal silica with silica particles and / or alumina particles Preliminary silica particles and / or alumina particles are added to an aqueous solution adjusted to a predetermined pH (alkaline), and then a high-shear stirrer or medium mill A predetermined dispersion of silica particles and / or alumina particles (slurry) is prepared by stirring for a predetermined time, and then various additives are added to the prepared dispersion as necessary. Is added to the colloidal silica in a desired ratio, and then mixed and stirred for a predetermined time with a known stirrer such as a blade stirrer or an inverted stirrer. As a result, the intended precision polishing composition for hard and brittle materials is obtained. Thus, when obtaining a dispersion of an abrasive that tends to cause problems such as thickening and gelation, a pH range (dispersion region) in which these particles can be dispersed in order to avoid such problems. It is desirable to adopt a method in which an aqueous solution of the above is prepared in advance and the particles are added and dispersed to form a particle dispersion in advance, and then added to the colloidal silica and mixed.

Polishing composition consisting of colloidal silica + polishing accelerator In advance, a polishing accelerator liquid is added to an aqueous solution adjusted to a predetermined pH (alkaline) by adding a polishing accelerator and, if necessary, various additives. Then, such a polishing accelerator liquid is added to colloidal silica and mixed and stirred to obtain the intended precision polishing composition for hard and brittle materials. Thus, it is desirable to add a chelating compound to an aqueous solution that has been previously adjusted to be alkaline with a pH adjuster such as aqueous ammonia or sodium hydroxide. However, when these chelating compounds are added, particularly when the chelating compound is an acid, the addition reduces the pH of the precision polishing composition for hard and brittle materials, and the properties of colloidal silica are reduced. This is because there is a possibility that problems such as destruction or gelation may occur.

  When the precision polishing composition according to the present invention is used to perform a precision polishing process on a hard and brittle material, conventionally known various polishing techniques are appropriately selected and implemented. For example, a predetermined amount of a precision polishing composition for hard and brittle materials is put into a supply container provided in a polishing machine, and a polyurethane or the like stuck on the surface plate of the polishing machine using a nozzle or a tube from the supply container While dropping and supplying the polishing composition to the polishing cloth comprising the above, by pressing the polishing surface of the hard and brittle material (wafer) against the polishing cloth surface, and rotating the platen at a predetermined rotation speed, The wafer surface is precisely polished (polished).

  Hereinafter, representative examples of the present invention will be shown to clarify the present invention more specifically, but the present invention is not limited by the description of such examples. It goes without saying. In addition to the following examples, the present invention includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the specific description described above. It should be understood that improvements can be made.

Preparation of Precision Polishing Composition for Hard and Brittle Materials Test Examples 1 to 13 which are precision polishing compositions for hard and brittle materials, and Comparative Examples by the methods shown below so that the blending ratios shown in Tables 1 and 2 below are obtained. 1-5 various polishing compositions were prepared.

Test example 1
100 g of commercially available amorphous silicon dioxide (average particle size: 1.8 μm, BET specific surface area: 180 m ² / g) was added to 500 g of an alkaline aqueous solution adjusted to pH = 9.5 with sodium hydroxide, Commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50% by weight, pH = 11) was added to 600 g of an aqueous dispersion of amorphous silicon dioxide obtained by stirring and dispersing for 30 minutes in a shear mixer homomixer. 400 g was added and mixed and stirred for 30 minutes with a blade stirrer to obtain 1 kg of a uniform polishing composition.

Test example 2
In the same manner as in Test Example 1, instead of amorphous silicon dioxide, 100 g of commercially available fumed silica (average primary particle diameter: 16 nm, BET specific surface area: 130 m ² / g) was used, and 1 kg of the polishing composition was used. Obtained.

Test example 3
100 g of commercially available amorphous silicon dioxide (average particle size: 1.8 μm, BET specific surface area: 180 m ² / g) was added to 450 g of an alkaline aqueous solution adjusted to pH = 9.5 with sodium hydroxide, A commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50% by weight, pH = 11) was added to 550 g of a dispersed aqueous solution of amorphous silicon dioxide obtained by stirring and dispersing for 30 minutes with a homogenizer of a shear stirrer. By adding 400 g, and further adding 50 g of an aqueous solution in which 8 g of ethylenediaminetetraacetic acid diammonium salt (EDTA · 2NH ₄ ) as a polishing accelerator was dissolved, and mixing and stirring for 30 minutes with a blade stirrer, 1 kg of a uniform polishing composition was obtained.

Test example 4, 5
600 g of commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50 wt%, pH = 11) and colloidal silica having an average particle size different from that (average particle size: 80 nm or 15 nm, solid content: 40 weight) %, PH = 10) 250 g was mixed and stirred, and further 150 g of an alkaline aqueous solution adjusted to pH = 9.5 was added with a 5% aqueous sodium hydroxide solution and stirred to obtain a total solid of colloidal silica. 1 kg of a uniform polishing composition having an amount of 40% by weight was obtained.

Test Example 6
As in Test Example 5, 400 g of commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50 wt%, pH = 11), colloidal silica having an average particle size different from that (average particle size: 15 nm, 250 g of solid content: 40 wt%, pH = 10) was mixed and stirred, and further, 100 g of commercially available amorphous silicon dioxide (average particle size: 3.6 μm, BET specific surface area: 150 m ² / g) A dispersion solution of amorphous silicon dioxide (silica slurry) dispersed with a high shear stirrer was added to 250 g of an alkaline aqueous solution adjusted to pH = 9.5 with a 5% aqueous sodium hydroxide solution, and mixed with a blade stirrer. By stirring, 1 kg of a uniform polishing composition was obtained.

Test example 7
Similar to Test Example 6, commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50% by weight, pH = 11) 600 g, colloidal silica having an average particle size different from that (average particle size: 15 nm, Solid content: 40 wt%, pH = 10) 250 g was mixed and stirred, and 8 g of EDTA · 2NH ₄ as a polishing accelerator was adjusted to pH = 9.5 with 5% aqueous sodium hydroxide solution. 150 g of the solution dissolved in the alkaline aqueous solution was added, and mixed and stirred for 30 minutes with a blade stirrer to obtain 1 kg of a uniform polishing composition.

Test examples 8-10
800 g of commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50 wt%, pH = 11), 8 g of EDTA · 2NH ₄ , phosphonobutane tricarboxylic acid (PBTC), or ethylenediaminetetraacetic acid dicalcium salt 200 g of a solution in which (EDTA · 2Ca) was dissolved in an alkaline aqueous solution adjusted to pH = 9.5 with a 5% aqueous sodium hydroxide solution was added and stirred to obtain 1 kg of a uniform polishing composition.

Test example 11
800 g of commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50% by weight, pH = 11) and 6 g of fumed alumina (average particle size of primary particles: 20 nm, BET specific surface area: 100 m ² / g) By adding 200 g of slurry dispersed with a high shear stirrer to an alkaline aqueous solution adjusted to pH = 9.5 with 5% aqueous sodium hydroxide solution, and finally mixing and stirring for 30 minutes with a blade stirrer 1 kg of a uniform polishing composition was obtained.

Test Example 12
Similarly to Test Example 11, 800 g of commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50% by weight, pH = 11) was added to fumed alumina (average particle size of primary particles: 20 nm, BET specific surface area: 100 g ² / g) 6 g was added to 192 g of slurry dispersed with a high shear stirrer in an alkaline aqueous solution adjusted to pH = 9.5 with 5% aqueous sodium hydroxide solution, and further 8 g of EDTA · 2NH ₄ Was added and mixed and stirred with a blade stirrer to obtain 1 kg of a uniform polishing composition.

Test Example 13
In the same manner as in Test Example 6, 400 g of commercially available alkaline colloidal silica (average particle size: 40 nm, solid content: 50% by weight, pH = 11), colloidal silica having an average particle size different from that (average particle size: 15 nm, 250 g of solid content: 40% by weight, pH = 10) was mixed and stirred. Further, 100 g of commercially available fumed silica (average particle size of primary particles: 16 nm, BET specific surface area: 130 m ² / g) Add 342 g of slurry dispersed with a high shear stirrer to an alkaline aqueous solution adjusted to pH = 9.5 with 5% sodium hydroxide, and then add 8 g of EDTA disodium salt (EDTA · 2Na). By mixing and stirring with a blade stirrer, 1 kg of a uniform polishing composition was obtained.

Comparative Examples 1-4
For comparison with Test Examples 1 to 13, 1 kg of a polishing composition was prepared, in which one kind of colloidal silica having the same particle diameter was blended alone. In Comparative Example 1, the above colloidal silica (average particle size: 40 nm, solid content: 50 wt%, pH = 11) was adjusted to 600 g with 5% aqueous sodium hydroxide solution and adjusted to pH = 9.5. 400 g of an aqueous solution was mixed and stirred. In Comparative Examples 2 and 3, 1 kg of colloidal silica (solid content: 40% by weight) having an average particle diameter of 80 nm or 15 nm was used as it was. Then, by adding 200 g of an aqueous solution adjusted to pH = 9.5 to 800 g of colloidal silica (average particle size: 40 nm, solid content: 50 wt%, pH = 11), 1 kg of a uniform polishing composition, respectively. Prepared.

Comparative Example 5
Also, α-alumina (average particle size: 0.5 μm, BET specific surface area) extremely hard compared to colloidal silica relative to colloidal silica (average particle size: 40 nm, solid content: 50 wt%, pH = 11). A polishing composition in which 5 m ² / g) was dispersed and contained was prepared for comparison. That is, first, 100 g of α-alumina and 500 g of dispersed water were added to a pot mill to prepare an α-alumina dispersion solution (α-alumina slurry) that was pulverized and dispersed for 70 hours, and the α-alumina slurry thus prepared was prepared. 600 g was stirred and mixed with 400 g of colloidal silica to obtain 1 kg of a polishing composition.

Polishing Test Each of 1 kg of the polishing compositions of Test Examples 1 to 13 and Comparative Examples 1 to 5 obtained above was provided in a polishing machine (Fujikoshi Co., Ltd .: SLM-100, polishing surface plate diameter: 350 mm). Then, the surface of a wafer (diameter: 75 mm) made of a lithium tantalate single crystal material was polished (precisely polished) for 5 hours using the polishing machine. In this polishing, the rotation speed (rotation speed) of the surface plate was set to 60 rpm, and the polishing pressure was 200 g / cm ² . The polishing composition is supplied onto the polishing cloth surface affixed on the surface plate at a supply rate of 200 mL / min using a tube pump, and the overflowing polishing composition is returned to the container. It was used repeatedly by the so-called circulation supply system.

  Then, while polishing the surface of the wafer as described above, each time the polishing time is 1 hour, the thickness of the wafer is measured using a micrometer (manufactured by Mitoyo, measurement accuracy: 1 μm), Obtain the polishing rate (μm / Hr) every hour, and observe the polished surface of the wafer with a differential interference microscope (manufactured by Leica, Germany: microscope) at a magnification of 40 times. Through the presence or absence of pits, the surface state of the polished surface at the initial stage of polishing was evaluated, and the results are also shown in Table 3 below.

  As apparent from Table 3, in Test Examples 4 and 5 in which two colloidal silicas having different particle sizes were blended and the particle size distribution was wide, compared with Comparative Examples 1 to 4 having a narrower particle size distribution. Thus, the polishing rate and the polishing life are improved while ensuring the excellent surface properties of the polished surface. And even if it is in Test Examples 8 to 10 in which a chelating compound as a polishing accelerator is added to colloidal silica, it is superior to Comparative Examples 1 to 4 in which such a polishing accelerator is not added. Improvements in polishing speed and polishing life have been achieved. And in Test Examples 7 and 13 in which colloidal silica and a chelating compound having different particle sizes are combined with colloidal silica as a base abrasive, a combination of a plurality of these results in even better polishing characteristics. It can be seen that is given.

Further, in Comparative Example 5 in which α-alumina (average particle size: 0.5 μm, BET specific surface area 5 m ² / g), which is an extremely hard abrasive, is mixed with colloidal silica, the polishing rate is extremely high. Although it becomes high, it turns out that surface defects, such as a pit and a scratch, are caused.

As is clear from the above explanation, colloidal silica (base abrasive) is combined with colloidal silica having a different average particle size from colloidal silica as the base abrasive, and a polishing accelerator composed of a chelating compound is added. In addition, in the precise polishing composition for hard and brittle materials, and also in the precise polishing composition for hard and brittle materials in which predetermined silica particles and / or alumina particles are combined, polishing of pits, scratches, processing strains, etc. The occurrence of defects can be effectively avoided, the surface of hard and brittle materials can be precisely polished to a very clean mirror surface, the polishing rate can be advantageously improved, and the time spent for polishing can be shortened, In this case, an excellent polishing life can be realized such that the polishing rate is maintained for a long time. In addition, by improving the polishing speed and the polishing life, it is possible to improve the working efficiency and workability in precision polishing and to enjoy good economic efficiency.

Claims (10)

  At least one second colloidal silica having an average particle size different from that of the first colloidal silica is added to and contained in the first colloidal silica, and a chelating compound is further added and contained as a polishing accelerator. A precision polishing composition for hard and brittle materials, characterized by being caulked.   The first colloidal silica is contained in a solid content of 10 to 50% by weight, and the total amount of the first colloidal silica and the second colloidal silica is 20 to 60% by weight. The precision polishing composition for hard and brittle materials according to claim 1, which is contained in a proportion of%.   The average particle diameter of the first colloidal silica is 30 to 60 nm, while the average particle diameter of the second colloidal silica is 5 to 22 nm or 80 to 100 nm, and the first colloidal silica and the second colloidal silica The precision polishing composition for hard and brittle materials according to claim 1 or 2, wherein the colloidal silica is used in a ratio of 60 to 80% and 40 to 20% by weight ratio of the solid content.   The precision for hard and brittle materials according to any one of claims 1 to 3, wherein the polishing accelerator is at least one of a polyaminocarboxylic acid chelating compound and an organic phosphonic acid chelating compound. Polishing composition.   The precision polishing composition for hard and brittle materials according to any one of claims 1 to 4, wherein the polishing accelerator is contained in a proportion of 0.1 to 5.0% by weight.   At least one of the second colloidal silica having an average particle size different from that of the first colloidal silica is added to and contained in the first colloidal silica, and at least one of the silica particles and the alumina particles. A precise polishing composition for hard and brittle materials, characterized in that a chelating compound is added and contained as a polishing accelerator.   The precision polishing composition for hard and brittle materials according to claim 6, wherein the silica particles are amorphous silicon dioxide and fumed silica, and the alumina particles are fumed alumina.   The precision polishing composition for hard and brittle materials according to claim 6 or 7, wherein at least one of the silica particles and the alumina particles is contained in a total amount of 2 to 25% by weight. .   The precision polishing composition for hard and brittle materials according to any one of claims 1 to 8, wherein the pH is adjusted to an alkalinity of 7 to 11. The precision polishing composition for hard and brittle materials according to any one of claims 1 to 9, wherein the hard and brittle material is a lithium tantalate single crystal material or a lithium niobate single crystal material.