JP2002170791A - Particle diffusion type mixedly functional fluid and machining method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle diffusion type mixedly functional fluid capable of improving the efficiency of existing precision treatment such as various precision machining parts such as a semiconductor silicon wafer, removal of a foreign matter or burr adhered on a surface and in a hole, finish of a side face of a recessed part or finish and cleaning of a side part of the recessed part, and capable of being used for finish machining of a cut face of an optical fiber, and to provide a machining method using the same. SOLUTION: The fluid is obtained by diffusing, as diffusion particles, (a) ferromagnetic particles having diameters of 0.5-50 μm and either one or both of (b) grit fine particles such as semiconductor particles or metallic particles having diameters of 0.1-50 μm and (c) magnetic fine particles having diameters of 25 nm or less, in a diffusion medium such as kerosine or silicon oil having kinematic viscosity of some 1-10,000 mm2/s and having electric insulation property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to finish polishing of various precision machined parts such as semiconductor silicon wafers, removal of foreign matter or burrs adhering to the surface or in holes, finishing of concave side surfaces, and finishing and cleaning of side portions. The present invention relates to a particle-dispersed mixed functional fluid that can be used for improving the efficiency of existing precision finishing processing, finishing a cut surface of an optical fiber, and the like, and a processing method using the same.

[0002]

2. Description of the Related Art In recent years, research on various functional fluids such as a magnetic fluid, a magnetic field responsive (MR) fluid, and an electric field responsive (ER) fluid which respond to a magnetic field or an electric field has been activated, and some of them have been commercialized. Some are being developed, but new developments are required in application development. For example, in processing such as polishing and finishing, an example using a magnetic fluid is known. In this case, since the polishing action can hardly be expected on the fine magnetic fine particles in the magnetic fluid, a mixed fluid in which the abrasive fine particles are dispersed is used, and the abrasive particles are held by the magnetic fluid induced by the magnetic field. Polishing is performed. But,
Polishing with such a magnetic fluid is suitable when the surface to be processed has a special shape such as a spherical surface. However, since the magnetization intensity is small, the polishing efficiency is low and a long polishing time is required. There is a current situation that the expansion of applications is not progressing. In addition, since the MR fluid has ferromagnetic particles such as iron powder dispersed therein, the ferromagnetic particles dispersed by the application of a magnetic field are promptly induced and aggregated to form an acicular shape having high mechanical strength. It has high polishing efficiency because it forms (beaded) clusters (magnetic needles). However, in the polishing using such an MR fluid, it is difficult to control the magnetic needles, and a magnetic needle having a relatively large thickness and a non-uniform shape and strength is formed. When added, scratch marks are formed on the surface to be processed by the magnetic needles. That is, such an MR fluid can be used for rough primary polishing (grinding), but cannot be used for processing such as finer polishing and finishing. Further, the fact that iron powder having a large particle diameter is generally used as a dispersoid (dispersed particles) in the MR fluid is also unsuitable for processing such as fine polishing and finishing.

[0003]

Accordingly, the present inventors have developed a new functional fluid having unprecedented effective characteristics, and have solved the above-mentioned problems in polishing with a magnetic fluid and polishing with an MR fluid. It is an object of the present invention to propose a processing method that can be suitably applied to processing such as polishing and finishing.

[0004]

The present invention has been proposed in view of the above and has a kinematic viscosity of 1 to 10,000 mm ² / s.
In a dispersion medium such as kerosene or silicone oil having an electrical insulating property, as dispersed particles, (a) particle diameter of 0.5 to 50
10 to 40 wt% of ferromagnetic particles having a particle size of (b)
Abrasive fine particles 10 of semiconductor particles or metal particles of 1 to 50 μm
The present invention relates to a particle-dispersed mixed functional fluid in which 40 wt% is dispersed.

[0005] The present invention also relates to the present invention, as the dispersion particles, (a) ferromagnetic particles 1 having a particle diameter of 0.5 to 50 µm in the dispersion medium.
The present invention also proposes a particle-dispersed mixed functional fluid in which 0 to 40 wt% and (c) 5 to 20 wt% of magnetic fine particles having a particle diameter of 25 nm or less are dispersed.

Further, the present invention provides a method for preparing a dispersion medium comprising: (a) 10 to 40 wt% of ferromagnetic particles having a particle diameter of 0.5 to 50 μm; 10-40 wt% of abrasive particles of semiconductor particles and metal particles
(c) Also proposed is a particle-dispersed mixed functional fluid in which 5 to 20 wt% of magnetic fine particles having a particle diameter of 25 nm or less are dispersed.

Further, the present invention is characterized in that the particles are processed while repeatedly applying a fluctuating magnetic field whose polarity changes in a state in which the particle-dispersed mixed functional fluid faces the surface of the sample to be processed. A processing method using a dispersed mixed functional fluid is also proposed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the materials constituting the particle-dispersed mixed functional fluid of the present invention will be described. As the dispersion medium, a solvent having a kinematic viscosity of about 1 to 10000 mm ² / s having an electrical insulating property is used, and for example, kerosene, silicone oil, or the like is used.

As described above, (a) ferromagnetic particles, (b) abrasive particles, and (c) magnetic particles are used as the dispersed particles. (a) The ferromagnetic particles have a particle diameter of 0.
Particles having a particle size of 5 to 50 μm, preferably a particle size of 1 to 1
Particles of 0 μm are used, and as a material, a dispersoid usually used as an MR fluid, for example, iron or a metal exhibiting ferromagnetism is used. (b) The abrasive fine particles are particles having a particle diameter of 0.1 to 50 μm made of a semiconductor material or a metal material, and the particle diameter to be applied differs depending on the surface roughness of the object to be polished. Examples of the material include diamond, corundum, emery, garnet, silica, calcined dolomite, fused alumina, artificial emery, silicon carbide, zirconia, chromium oxide, silicon oxide, iron oxide, calcium oxide, magnesium oxide, cerium oxide, magnesium carbide, Barium carbonate or the like is used, and the hardness (material), particle size, and the like may be selected according to the material of the surface to be processed and the processing accuracy. (c) As the magnetic fine particles, particles having a particle diameter of 25 nm or less, preferably about 10 nm are used. A dispersoid usually used as a magnetic fluid, such as magnetite, may be used. Further, a dispersion stabilizing aid such as various surfactants may be blended for the purpose of improving dispersibility.

[0010] The mixing ratio of the dispersed particles was determined as follows. (a) The mixing ratio of the ferromagnetic particles is 10 to 40% by weight. If the mixing ratio is less than 10% by weight, the ability to hold the abrasive grains is reduced, and the polishing efficiency is reduced. If the content is more than 40 wt%, aggregation easily occurs and scratch marks easily occur, so that the polishing characteristics are suppressed. (b) The mixing ratio of the abrasive particles is 10 to 40 wt%, but if it is less than 10 wt%, the polishing efficiency is reduced. 4
If it is more than 0 wt%, the fluidity is reduced and the rolling properties of the abrasive grains are reduced, so that the polishing characteristics are suppressed. (c) The mixing ratio of the magnetic fine particles is 5 to 20 wt%, but if it is less than 5 wt%, (a) the ferromagnetic particles are not wrapped and aggregation is easily caused, so that the polishing characteristics are deteriorated. 2
If the content is more than 0 wt%, (b) the force for holding the abrasive particles is reduced, so that the polishing efficiency is reduced.

As described above, the particle-dispersed mixed functional fluid of the present invention contains (a) a particle diameter of 0.5 to 50 μm as dispersed particles.
(B) particle size of 0.1 to 50
It is a configuration using one or both of abrasive fine particles of semiconductor particles and metal particles of μm and (c) magnetic fine particles having a particle diameter of 25 nm or less, and when a magnetic field is applied to a fluid having such a structure. The behavior of the dispersed particles in the fluid will be described below.

When a magnetic field is applied to the particle-dispersed mixed functional fluid of the present invention, (a) the ferromagnetic particles are mutually adsorbed to form a magnetic needle like a conventional MR fluid.
As described above, (a) MR in which only ferromagnetic particles are dispersed
The fluid forms magnetic needles that are relatively thick and non-uniform in shape and strength. However, in the particle-dispersed mixed functional fluid of the present invention, not only (a) ferromagnetic particles but also smaller (b) abrasive particles and (c) magnetic particles are dispersed. b) abrasive grains and (c) magnetic fine particles cover the periphery of (a) ferromagnetic particles, it is considered that a magnetic shield phenomenon is exhibited, (a) the distance between ferromagnetic particles is widened,
The suction power is also reduced and averaged. Therefore, in the particle-dispersed mixed functional fluid of the present invention, the magnetic needles have improved thickness, mechanical strength, and non-uniform generation distribution, and are relatively thin and have uniform shape, strength, and uniform distribution. A shape is formed. The mechanical strength of the magnetic needles is lower (softer) than that of the MR fluid. These magnetic needles are attracted and concentrated on the surface to be processed. On the other hand, when the application of the magnetic field is cancelled, each dispersed particle is uniformly and uniformly dispersed and fluidized. In particular, it has been found that particularly (b) the abrasive fine particles are discharged (localized) to the surface of the formed magnetic needle-like body, and play an effect of promoting the processing efficiency of the magnetic needle-like body. That is, as described above, although the magnetic needle-shaped body is soft and relatively thin, an improvement in processing is recognized,
Generally, iron powder or the like having a large particle diameter is used as the ferromagnetic particles (a) forming the magnetic needle-shaped body, so that it is not sufficiently satisfactory for processing with higher precision. Small and hard (b) fine abrasive particles are localized on the surface of the magnetic needle-shaped body, thereby further promoting the processing efficiency and performing processing in a shorter time with higher processing accuracy. be able to.

However, even with the particle-dispersed mixed functional fluid of the present invention, a sufficiently satisfactory processing cannot be obtained when a DC magnetic field is applied. For example, when finishing is taken as an example, it is not possible to obtain a finished surface whose surface roughness is close to a mirror surface. Therefore, the processing method of the present invention provides an appropriate fluctuating magnetic field as described above, and further slides relatively to the surface to be processed, so that the particle-dispersed mixed functional fluid facing the surface to be processed. Among them, the formation (solidification), rolling, and liquefaction of the magnetic needle-shaped body having the above characteristics are continuously repeated, and excellent effects (unsatisfactory processing) such as polishing and finishing have not been achieved in the past. ) Is obtained.

In the processing method of the present invention, instead of applying a DC magnetic field as described above, a low-frequency magnetic field of 0.01 to 10 Hz is basically formed by a square wave whose polarity changes repeatedly, and a repetitive polarity or pulse-like waveform is formed. , Giving a fluctuating magnetic field of 30 to 70%. In particular, it is desirable to use a square wave with a good rise in machining with a large machining amount and a sine wave with a gentle rise in machining with a small machining amount.

As described above, the processing method of the present invention performs the processing while applying the above-mentioned fluctuating magnetic field to the particle-dispersed mixed functional fluid having the above-mentioned structure. Disperse (a) ferromagnetic particles, (b) abrasive particles, and (c) magnetic particles more than a binary fluid in which (a) ferromagnetic particles and (b) abrasive particles are dispersed in a medium. The processed three-component fluid can perform finer processing. That is, the effect of (a) covering the periphery of the ferromagnetic particles, extending the distance and lowering the attraction force to average out is somewhat expected from (b) abrasive fine particles, but only (c) magnetic fine particles (magnetic Fluid).

The processing method of the present invention is applicable not only to a processing surface having a flat surface, but also to a processing surface having a stepped shape or a spherical shape, or any material. Can be applied to the surface to be processed, and easy and fine processing can be obtained.

(B) The particle-dispersed mixed functional fluid of the present invention which does not contain abrasive particles is a so-called conventional magnetic fluid and an MR mixed fluid.
It has a configuration mixed with a fluid. It has been found that the fluid with this configuration has a clearly superior responsiveness when a magnetic field is applied and released when compared to a magnetic fluid, and can form a stronger structure than a magnetic fluid when a magnetic field is applied. Was done. It has also been found that the structure when a magnetic field is applied is extremely homogeneous as compared with the MR fluid. That is, they have the property of sharing both advantages. Therefore, it is expected to be used in various fields as a sealing material in various sealing structures, for example.

[0018]

EXAMPLES [Polishing Example 1] In a kerosene dispersion medium, Table 1 was used.
A fluid was prepared by dispersing the dispersed particles shown in Table 1 below, and was polished under the following conditions. The results are shown in Table 1. <Polishing sample> Surface roughness before polishing: Ry = approximately 2 μm Material: pure titanium <Polishing condition> Number of rotations of the rotating processing surface: 15 rpm Processing pressure: 5 kg Polishing time: 5 minutes

[0019]

[Table 1]

Polishing Example 2 First, a particle-dispersed mixed functional fluid shown in Table 2 was prepared.

[Table 2] Polishing was performed using the particle-dispersed mixed functional fluid under the following conditions.

<Polishing condition a> Magnetic field: fluctuating magnetic field (square wave), magnetic field strength 1300 gauss,
Frequency 0.1 Hz Number of rotations of the rotating processing surface: 15 rpm Processing pressure: 5 kg Polishing time: 5 minutes <Polishing sample a> Material: Pure titanium Surface roughness before polishing: Ra = 0.37 μm, Ry = 1.94
μm <Test result a> Duty ratio 30% Polished surface roughness: Ra = 0.13 μm, Ry = 0.63
μm

<Polishing condition b; Comparative example 1> Magnetic field: None Number of rotations of the rotating processing surface: 15 rpm Processing pressure: 5 kg Polishing time: 5 minutes <Polishing sample b> Material: Pure titanium Surface roughness before polishing: Ra = 0 .36 μm, Ry = 1.98
μm <Test result b> Surface roughness after polishing: Ra = 0.29 μm, Ry = 1.18
μm

<Polishing condition c; Comparative example 2> Magnetic field: DC magnetic field, magnetic field strength 2300 gauss Number of rotations of the rotating processing surface: 15 rpm Processing pressure: 5 kg Polishing time: 5 minutes <Polishing sample c> Material: Pure titanium Surface before polishing Roughness: Ra = 0.37 μm, Ry = 1.96
μm <Test result c> Surface roughness after polishing: Ra = 0.33 μm, Ry = 1.34
μm

Under the polishing condition a, which is an embodiment of the present invention, it is confirmed that the processing is performed while applying an appropriate low-frequency fluctuating magnetic field, so that processing with extremely high polishing accuracy can be performed in a short time. On the other hand, under the polishing condition b in which no magnetic field was applied or the polishing condition c in which a DC magnetic field was applied, satisfactory polishing was not performed.

In the above polishing conditions a to c, a rotary platen having a polishing pad attached to the surface was used, but processing was carried out for 5 minutes in exactly the same manner as in the above polishing condition a except that there was no polishing pad. As a result, the improvement in the surface roughness was smaller than in the polishing condition a using the polishing pad.

In the polishing condition a, the applied magnetic field was a square wave having a good rise, but three kinds of polishing samples having different surface roughnesses were prepared for comparison with a sine wave having a gentle rise, and the polishing time was changed. The processing was performed in exactly the same manner as the polishing condition a except that the time was changed to 10 minutes. The results are shown in Table 3.

[Table 3] As is clear from Table 3, the waveform of the applied magnetic field is preferably a square wave with a good rise in machining with a large machining amount, and a sine wave with a slow rise is preferred in machining with a small machining amount. Was.

Although several embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be implemented in any manner unless the configuration described in the claims is changed. It is possible.

[0028]

As described above, the particle-dispersed mixed functional fluid of the present invention and the processing method using the same can be performed in a short time.
Fine polishing and finishing can be performed with sufficiently high polishing accuracy. Therefore, finish polishing of various precision processed parts such as semiconductor silicon wafers, which cannot be applied by the method using the conventional magnetic fluid or MR fluid,
Suitable for improving the efficiency of existing precision finishing processes, such as removing foreign matter or burrs attached to the surface or inside of holes, finishing the side surfaces of concave portions, finishing or cleaning side portions, and finishing optical fiber cut surfaces. Available.

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Claims (7)

[Claims] In a dispersion medium such as kerosene or silicone oil having an electrical insulating property with a kinematic viscosity of 1 to 10000 mm ² / s, ferromagnetic particles having a particle diameter of 0.5 to 50 μm are dispersed in a dispersion medium of 10 to 40 wt%. And a particle-dispersed mixed functional fluid comprising 10 to 40% by weight of abrasive particles of semiconductor particles or metal particles having a particle diameter of 0.1 to 50 [mu] m. 2. A ferromagnetic particle having a particle diameter of 0.5 to 50 μm as a dispersion particle in a dispersion medium such as kerosene or silicone oil having a kinematic viscosity of 1 to 10000 mm ² / s and having electrical insulation properties. And 5 to 20 wt% of magnetic fine particles having a particle diameter of 25 nm or less. 3. A ferromagnetic particle having a particle diameter of 0.5 to 50 μm as a dispersion particle in a dispersion medium such as kerosene or silicone oil having a kinematic viscosity of 1 to 10000 mm ² / s and having electrical insulation properties. Abrasive fine particles of semiconductor particles or metal particles having a particle diameter of 0.1 to 50 μm 10 to 40 wt%
And 5 to 20 wt% of magnetic fine particles having a particle diameter of 25 nm or less.
And a particle-dispersed mixed functional fluid characterized by being dispersed. 4. A process while repeatedly applying a fluctuating magnetic field whose polarity repeatedly changes while the particle-dispersed mixed functional fluid according to any one of claims 1 to 3 faces a surface to be processed of a processed sample. A processing method using a particle-dispersed mixed functional fluid, which is performed. 5. The particle-dispersed mixed functional fluid according to any one of claims 1 to 3 is interposed between a rotary platen having a processing pad attached to a surface thereof and a processing surface of a processing sample. A process using a particle-dispersed mixed functional fluid, wherein the process is performed by applying a working surface pressure together with a fluctuating magnetic field while relatively sliding. 6. An applied magnetic field has a magnetic field strength of ± 1 at a processing portion.
The particle dispersion according to claim 4 or 5, wherein a fluctuating magnetic field having a duty ratio of 30 to 70% is applied as a repetitive square wave or a pulse wave having a frequency of 0.01 to 3000 gauss and a frequency of 0.01 to 10 Hz. Processing method using mold mixed functional fluid. 7. The processing method according to claim 4, wherein the applied magnetic field is a square wave with a good rise in the processing with a large processing amount, and a sine wave with a gentle rising in the processing with a small processing amount. A processing method using the particle-dispersed mixed functional fluid according to any one of the above.