JP2000167770A - Machining method by high speed shear stream - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a machining tank compact, prevent organic contamination of machining liquid, stabilize flow, control a gap easily, eliminate external disturbance due to influencing of coarse particles in machining liquid, and perform high quality machining with high efficiency by generating shear stream having controlled scope and distribution and speed gradient exceeding a fixed speed gradient along a surface of a workpiece without using a rotor. SOLUTION: A workpiece 2 and a high pressure nozzle 1 are arranged at a predetermined interval in a machining tank containing ultra-pure water mostly to generate high speed shear stream of ultra-pure water injected from the high pressure nozzle in the vicinity of a surface of the workpiece. Minute particles chemically reactive to the workpiece are supplied to the surface of the workpiece due to flow of ultra-pure water, and minute particles chemically combined with the workpiece are removed by high speed shear stream to remove atoms on the surface of the workpiece and promote machining.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method using a high-speed shear flow in which fine particles are brought into flow contact with a processing surface of a workpiece to perform processing without causing distortion, cracks, thermal deterioration and the like at all.

[0002]

2. ^{Description of the} Related Art Conventionally, a working fluid comprising a suspension in which fine particles having a particle size of 10 ^-9 to 10 ^-6 m are dispersed is caused to flow along a processing surface of a workpiece to deposit the fine particles on the processing surface. The so-called EEM (elastic emulation) process, in which contact is made with almost no load, and the fine particles and the interaction at the interface of the processing surface (a kind of chemical bond) at that time removes the processing surface atoms in the order of atomic units.
Ultra-precision mirror finishing by ission Machining has been developed by the present inventors and is already known. This EEM is characterized in that an excellent surface crystallographically equivalent to that of chemical etching can be obtained and that it has processing controllability.

In conventional processing using EEM, a processing sphere or cylindrical body (rotating body) made of a low elastic modulus polymer material such as polyurethane is formed while maintaining a small gap with respect to a processing surface of a workpiece. Rotate to generate a machining fluid flow in the vicinity of the processing surface, and in the case of a sphere, scan the sphere over the entire processing surface to continue the point-like processing marks formed in the minute area on the processing surface, The entire surface is precisely processed into a free-form surface, and in the case of a cylindrical body, the workpiece is relatively translated in a direction inclined at a predetermined angle with respect to the axial direction of the cylindrical body,
Alternatively, the cylindrical body is reciprocated relatively in the axial direction, and the workpiece is relatively translated in a direction substantially perpendicular to the axial direction of the cylindrical body. Have already proposed an ultra-precision mirror finishing method. That is, in the conventional EEM, the powder particles are supplied to the surface of the workpiece by the elastic fluid lubrication flow generated by the rotating body facing the surface of the workpiece.

[0004] However, the conventional EEM has the following problems. First, in order to create a uniform flow in the minute gap between the rotating body and the workpiece, it is necessary to increase the size of the processing tank so that unnecessary flow generated around the rotating body does not affect the flow. there were. Also, since it was necessary to use a low-elastic modulus polymer material such as polyurethane for the material of the rotating body, not only was the dimensional accuracy and durability inferior, but also organic contamination of the working fluid occurred, and swelling and lubrication caused by water Therefore, there is a disadvantage that the rotating body is deformed and flow stability cannot be obtained. Still other problems are that only asymmetrical point-like machining marks can be obtained with a spherical rotating body, that the minute gap is about 1 μm, so that it is easily affected by the influence of coarse particles in the working fluid, and that the machining efficiency is low. It is mentioned.

[0005]

In the EEM, fine particles chemically reactive with the workpiece are supplied to the surface of the workpiece by using the flow of ultrapure water, and the surface of the workpiece and the fine particles are separated. When the fine particles are further removed from the surface of the workpiece by the flow after the chemical bonding occurs in the above, the fine particles carry away the atoms on the surface of the workpiece, whereby the processing proceeds. The present inventor theoretically predicts that a shear flow having a predetermined strength or more is required on the surface of the workpiece in order to remove fine particles attached to the surface of the workpiece with chemical bonding. This was confirmed in an experiment. In other words, the shape of the processing mark by the rotating body is made to correspond to the velocity gradient distribution of the shear flow by the rotating body, and it has been found that the processing requires a certain velocity gradient of the shear flow or more.

[0006] In view of the above situation, the present invention aims to solve the problem by applying a shear flow having a controlled range and distribution over a predetermined velocity gradient to the surface of a workpiece without using a rotating body. Accordingly, it is an object of the present invention to provide a processing method using a high-speed shear flow, which can solve the above-mentioned problems at once, and can perform high-quality processing with high efficiency.

[0007]

According to the present invention, in order to solve the above-mentioned problems, a workpiece and a high-pressure nozzle are arranged at a predetermined interval in a processing tank mainly composed of ultrapure water. In addition to generating a high-speed shear flow of ultrapure water injected from a high-pressure nozzle near the surface of the workpiece, the flow of ultrapure water causes fine particles chemically reactive with the workpiece to flow to the surface of the workpiece. A high-speed shearing flow method was developed in which the fine particles supplied and chemically bonded to the workpiece were removed by a high-speed shear flow to remove atoms on the surface of the workpiece, and the processing was advanced.

Here, when the high pressure nozzle has a circular hole, point processing can be performed, and the surface of the workpiece can be processed into an arbitrary shape. When the nozzle is a slit hole, line processing can be performed. In addition, the surface of the workpiece can be processed into a planar shape or a corrugated shape over a wide area.

Further, in the processing method of the present invention, the high-pressure nozzle jets a processing liquid in which fine particles are dispersed in ultrapure water, or jets ultrapure water from the high-pressure nozzle. Either a concentrated processing liquid in which fine particles are dispersed is discharged from a fine particle supply nozzle arranged in the vicinity, or a processing tank is filled with a processing liquid in which fine particles are dispersed in ultrapure water, and ultrapure water is injected from the high-pressure nozzle. You do it. Further, it is more preferable to arrange a collecting means on the downstream side of the high-speed shear flow generated by the high-pressure nozzle to collect the working fluid.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, in order to remove fine particles adhering to a workpiece surface along with a chemical bond, a shear flow intensity (velocity gradient) is required on the workpiece surface. Or estimated. When ZrO ₂ fine particles having a particle size of 0.1 μm are adsorbed on the Si (100) surface in ultrapure water, and a shear flow of ultrapure water of various strengths acts on this surface, the fine particles are removed from the Si surface. The state of removal was observed with an optical microscope. As a result, it was found that when the velocity gradient exceeded about 5 m / sec · μm, effective removal of fine particles proceeded. On the other hand, in the conventional EEM, the shape of the processing trace due to the rotating body and the shape of the region where the velocity gradient of the shear flow obtained by the simulation was about 5 m / sec · μm or more substantially matched. From these results, it was found that the processing required a shear flow of a certain speed gradient or higher, but the lower limit is expected to vary depending on the material of the workpiece and the type and particle size of the fine particles. .

According to the present invention, a high-pressure nozzle sprays ultrapure water or a suspension of ultrapure water and processing fine particles (processing liquid) onto a processing surface of a workpiece to generate a shear flow along the processing surface. In this method, the fine particles remove surface atoms from the surface of the workpiece by utilizing the chemical bonding force between the fine particles and the surface atoms of the workpiece. Therefore, the flow of the ultrapure water or the machining fluid injected from the high-pressure nozzle was calculated in the vicinity of the nozzle directly using a fluid analysis model.

In the analysis model, the nozzle is axially symmetrical at right angles to the surface of the workpiece, and Navier's
Stokes equation of motion was solved numerically by the difference method. The calculation is as follows: the hole diameter of the nozzle is 0.1 mmφ, the outer diameter is 2 m
mφ, and the gap between the nozzle tip and the surface of the workpiece is 1
mm and 2 mm. The supply pressure of the fluid to the nozzle was 1000 atm. At each gap, a pressure distribution, a flow distribution in a nozzle hole direction (Z-axis direction) and a radial direction (R direction) were obtained. FIG. 1 shows the results when the gap is 1 mm, and FIG. 2 shows the results when the gap is 2 mm.

From this calculation result, it is understood that the pressure loss due to the viscosity of the fluid in the analysis region is about 50 atm. At the inflow portion, a flow (about 450 m / sec) in the direction of the nozzle hole corresponding to a dynamic pressure of about 950 atm is generated (see FIG. 1 (a)), and this flow is generated in the vicinity of the surface of the workpiece (the workpiece). The vehicle decelerates after traveling almost straight to about 75 μm from the object surface. At that time, the dynamic pressure is converted to static pressure in the vicinity of the surface of the workpiece, and after a static pressure of about 950 atm is generated (see FIG. 1 (b)), the dynamic pressure is converted back to dynamic pressure as a radial flow. (Figure 1
(c)). The radial flow occurs in a very thin layer along the surface of the workpiece (approximately 2
(In the range of 5 μm), it has been found that the shear flow on the workpiece surface required in EEM can be generated very effectively. In addition, in the case of the gap of 1 mm and the case of 2 mm, almost the same flow occurs, which indicates that the gap control is extremely easy. Under this condition, the maximum velocity gradient on the workpiece surface is about 100 m / sec · μm even when the gap is 1 mm or 2 mm.

Next, the details of the present invention will be further described with reference to the accompanying drawings. FIGS. 3 to 5 show a conceptual structure of the high-pressure nozzle, in which a working fluid or ultrapure water is jetted from the tip of the high-pressure nozzle 1 to form a predetermined shear flow on the surface of the workpiece 2. . Here, when only the ultrapure water is jetted from the high-pressure nozzle 1, the processing liquid is supplied from another port in accordance with the flow of the ultrapure water. Alternatively, a processing liquid in which fine particles are dispersed in ultrapure water is filled in a processing tank in advance, and ultrapure water is sprayed from a high-pressure nozzle into the processing liquid, and a predetermined amount of water is similarly applied onto the surface of the workpiece 2. Make a shear flow.

FIG. 3 shows a structure in which a machining liquid in which ultrapure water and fine particles for processing are mixed is ejected from the ejection port 3 of the high-pressure nozzle 1, and FIG. FIG. 3B shows an oblique incidence type in which the direction of the ejection port 3 is inclined with respect to the surface of the workpiece 2. Here, when the injection port 3 is a circular hole, the surface of the workpiece 2 can be precisely free-curved by continuously forming point-like processing marks formed in a minute area on the processing surface. When the jet port 3 is a slit hole, a linear processing mark is formed on the processing surface, and the surface of the workpiece 2 can be flat and mirror-finished.

FIG. 4 shows a case in which only ultrapure water is jetted from the jet port 3 of the high-pressure nozzle 1 and a concentrated processing liquid in which fine particles for processing are fluidized with ultrapure water is supplied from a supply pipe 4. 4
(a) shows a case where the ultrapure water spouted from the spout 3 at the tip and the concentrated processing liquid are mixed through the supply pipe 4 into the spout 3 of the high-pressure nozzle 1 of the vertical incidence type to form the workpiece 2. FIG. 4B shows a structure in which a supply pipe 4 is arranged at a position facing a gap from the side of the high-pressure nozzle 1 of the oblique incidence type, and ultrapure water spouted from the spout 3 is shown in FIG. This is a structure in which a concentrated processing liquid is involved. Although not shown, FIG.
FIG. 3A shows a structure in which a supply pipe 4 is arranged at a position facing a gap from the side of a normal incidence type high-pressure nozzle 1, and the inside of the injection port 3 of the oblique incidence type high-pressure nozzle 1 shown in FIG. A structure through the supply pipe 4 is also possible. In any case, the ejection port 3 of the high-pressure nozzle 1 has a circular hole and a slit hole, and when the ejection port 3 is a slit hole, the supply pipe 4 is a flat tube or a thin circular tube. It is necessary to provide a plurality of rows.

Further, the machining fluid ejected from the ejection port 3 of the high pressure nozzle 1 or the concentrated machining fluid ejected from the supply pipe 4 is mixed with the ultrapure water ejected from the ejection port 3 immediately and efficiently. It is also possible to collect. This conceptual diagram is shown in FIG. FIG. 5A shows a recovery means in which a ring-shaped recovery plate 5 is arranged at a fixed interval around the tip of a high-pressure nozzle 1 of a vertical incidence type, and is disposed between the high-pressure nozzle 1 and the recovery plate 5. The working fluid is allowed to flow. FIG. 5B shows a collecting means in which a collecting plate 5 is partially disposed at a predetermined interval downstream of the processing liquid of the oblique incidence type high pressure nozzle 1.

Here, the material of the workpiece and the material of the fine particles for processing will be described briefly. The processing principle in the present invention is based on the interaction of a kind of chemical bond at the interface between the fine particles for processing and the surface of the workpiece, whereby the fine particles are bonded to the surface atoms, and are removed from the surface by a high-speed shear flow, whereby the fine particles are removed together with the fine particles. Since processing proceeds by removing surface atoms, the combination of the material of the workpiece and the material of the processing fine particles greatly affects the processing speed. If a silicon wafer (Si) is selected as the workpiece,
_The processing speed is higher when the ZrO ₂ powder is used than when the ZrO ₂ powder is used.

Next, a system for supplying high-pressure ultrapure water to the high-pressure nozzle 1 will be briefly described with reference to FIG. A plunger pump is used as the pressure generating pump 10. Also, if the ultrapure water for processing is directly pressurized by a pump, contamination of particles and the like generated in sliding parts in the pump becomes a problem, so the ultrapure water for processing is passed through a diaphragm or blow made of PTFE or SUS. The system which pressurizes water is adopted. Pressurizing parts 11 and 12 of ultrapure water are 2
The city water is pressurized to a predetermined pressure by one plunger pump 10 and the pressure is
It branches into a flow path and is connected to the pressurizing units 11 and 12 via valves 14 and 15, respectively. On the other hand, the ultrapure water for processing is connected from the ultrapure water supply device 16 to the pressurizing units 11 and 12 via valves 17 and 18, respectively. And
Each of the pressurizing parts 11 and 12 has a PTFE or SUS inside.
City water and ultrapure water are separated by diaphragms 19 and 20 made of
Ultrapure water is pressurized by the pressure of city water through the diaphragms 19 and 20, and the ultrapure water pressurized by the pressurizing units 11 and 12 is supplied to the valve 2.
The two are merged via the nozzles 1 and 22 and supplied to the high-pressure nozzle 1. A drain valve 23 is provided between the valve 14 and the pressurizing unit 11, and a drain valve 24 is provided between the valve 15 and the pressurizing unit 12. All these valves employ electromagnetic valves and can be opened and closed by a computer.

The operation of the high-pressure ultrapure water supply system is as follows. First, the ultrapure water supply device 16 produces ultrapure water having substantially the same pressure as the atmospheric pressure. Since it is difficult to continuously pressurize the ultrapure water, in the above-described system, the ultrapure water is alternately pressurized from atmospheric pressure to a predetermined pressure by the two pressurizing units 11 and 12, and the high-pressure nozzle 1 is pressurized. , High-pressure ultrapure water is continuously supplied. That is, in the system of one pressurizing unit 11, the valves 14 and 21 are opened, and the valves 17 and 23 are closed to supply pressurized city water into the pressurizing unit 11, and the diaphragm 19 in the pressurizing unit 11 is supplied. The pressurized ultrapure water is supplied to the high-pressure nozzle 1 through the
2 is closed, valves 18 and 24 are opened, and ultrapure water is supplied from the ultrapure water supply device 16 into the pressurizing unit 12 while draining city water from the pressurizing unit 12. Here, after opening the valve 24 to return the inside of the pressurizing section 12 to the atmospheric pressure, the valve 18 is opened so that the ultrapure water supply device 16 does not break down under pressure. Next, the valves 18 and 24 are closed, the valve 15 is opened to supply the pressurized city water into the pressurizing section 12, and the ultrapure water is pressurized to reach the supply pressure. , 1
4, the valve 23 is opened to drain the city water in the pressurizing unit 11 and the inside of the pressurizing unit 11 is brought to the atmospheric pressure. From 16, ultrapure water is supplied into the pressurizing section 11. Thereafter, this is a repetition, and the opening / closing timing of each valve is controlled by a computer, and high-pressure ultrapure water is continuously supplied to the high-pressure nozzle 1.
It is supplied to.

Next, FIG. 7 shows an example of a processing apparatus adopting the processing method by high-speed shear flow of the present invention. The processing apparatus 100 has a processing tank 101 filled with ultrapure water in an upper part, and a driving mechanism unit 1 having a built-in XY-θ driving system in a lower part.
2, the processing tank 101 and the drive mechanism 102 are partitioned by a non-magnetic partition wall 103 so that the inside of the processing tank 101 is not contaminated by particles or the like generated from a sliding portion of the drive system. In the processing tank 101, a high-pressure nozzle 1 connected to a Z-axis drive system 104 is provided at the upper part, and a sample table 105 provided horizontally and rotatably by ultrapure water static pressure support is provided at a lower part. The workpiece 2 is fixed and faces the high-pressure nozzle 1. The drive mechanism 102 includes an X-axis drive system 106 and a Y-axis drive system 10.
7 has an XY table 108 which is provided so as to be horizontally movable, and the XY table 108 is provided with a θ-axis drive system 109. The permanent magnet 110 fixed to the lower surface of the sample stage 105 and the permanent magnet 1 fixed to the θ-axis drive system 109
11 are opposed to each other via the partition 103 and are magnetically coupled to each other, and the displacement by the XY-θ drive system is changed by the permanent magnet 111,
The light is transmitted to the sample stage 105 via the permanent magnet 110.
As described above, the high-pressure nozzle 1 and the workpiece 2 can be relatively displaced in the XYZ-θ-axis directions by the respective driving systems, and the workpiece 2 is formed into a predetermined shape by the high-pressure nozzle 1. It can be processed.

In the processing apparatus 100, the same amount of ultrapure water injected from the high-pressure nozzle 1 and ultrapure water flowing into the processing tank 101 from the ultrapure water static pressure support of the sample stage 105 is used. A system for separating and extracting ultrapure water from the processing tank 101 by liquid phase separation is provided. The extracted ultrapure water is sent to the static pressure support unit again after the impurity concentration is reduced to the limit by a purification device. This system makes it possible to remove even trace amounts of metal ions and the like eluted from structures in the processing tank 101.

[0023]

According to the processing method using high-speed shear flow of the present invention as described above, a predetermined flow can be generated only in a necessary area, so that a processing apparatus can be downsized and a polymer material can be used. Since it is not used, the processing liquid is not contaminated by organic substances, and processing can be performed with a sufficiently large gap, so that gap control for stabilizing the flow is extremely easy, and disturbance such as mixing of coarse particles Stable against

[Brief description of the drawings]

FIG. 1 shows a simulation result of a pressure and a velocity component when ultrapure water is jetted at a right angle from a high-pressure nozzle to a surface of a workpiece with a gap of 1 mm, and FIG.
(b) shows the pressure distribution, and (c) shows the velocity component in the R direction.

FIG. 2 shows a simulation result of a pressure and a velocity component when ultrapure water is jetted at a right angle from a high-pressure nozzle to a surface of a workpiece with a gap of 2 mm, and (a) shows a velocity component in a Z direction;
(b) shows the pressure distribution, and (c) shows the velocity component in the R direction.

FIGS. 3A and 3B are simplified cross-sectional views showing the concept of a high-pressure nozzle for directly injecting a working fluid, wherein FIG. 3A shows a vertical incidence type and FIG. 3B shows an oblique incidence type.

FIG. 4 is a simplified cross-sectional view showing a concept of a type in which only ultrapure water is injected from a high-pressure nozzle and mixed with a concentrated processing liquid discharged from a separately provided supply pipe, and FIG. (B) shows a type in which a supply pipe is provided on the tip side of the high-pressure nozzle.

FIGS. 5A and 5B are simplified cross-sectional views showing a nozzle structure having a function of recovering a working fluid, wherein FIG. 5A is a structure in which a recovery plate is arranged around a high-pressure nozzle of a vertical incidence type, and FIG. The structure in which a collecting plate is arranged downstream of the incident type high pressure nozzle is shown.

FIG. 6 is a simplified piping diagram of a high-pressure ultrapure water supply system.

FIG. 7 is a simplified perspective view showing a processing apparatus employing the method of the present invention, partially cut away.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 High-pressure nozzle 2 Workpiece 3 Injection port 4 Supply pipe 5 Recovery plate (recovery means) 10 Pump 11,12 Pressurizing part 13 Regulator 14,15,17,18,21,22,23,24 Valve 16 Ultra pure Water supply device 19, 20 diaphragm 100 processing device 101 processing tank 102 drive mechanism unit 103 partition wall 104 Z-axis drive system 105 sample stage 106 X-axis drive system 107 Y-axis drive system 108 XY table 109 θ-axis drive system 110, 111 permanent magnet

Claims (7)

[Claims] 1. A workpiece and a high-pressure nozzle are disposed at a predetermined interval in a processing tank mainly composed of ultrapure water, and the ultrapure nozzle sprayed from the high-pressure nozzle near the surface of the workpiece. A high-speed shear flow of water is generated, and fine particles chemically reactive with the work are supplied to the surface of the work by the flow of ultrapure water, and the fine particles chemically bonded to the work are converted into a high-speed shear flow. A processing method using a high-speed shear flow, characterized in that the processing is carried out by removing the atoms on the surface of the workpiece by removal. 2. The processing method by high-speed shear flow according to claim 1, wherein the ejection port of the high-pressure nozzle is a circular hole. 3. The processing method according to claim 1, wherein the ejection port of the high-pressure nozzle is a slit hole. 4. The processing method according to claim 1, wherein a processing liquid in which fine particles are dispersed in ultrapure water is jetted from the high-pressure nozzle. 5. Injecting ultrapure water from the high pressure nozzle,
A concentrated processing liquid in which fine particles are dispersed is discharged from a fine particle supply nozzle disposed near the high pressure nozzle.
3. The processing method using a high-speed shear flow according to any one of 3. 6. A high-speed shear flow according to claim 1, wherein the processing tank is filled with a processing liquid in which fine particles are dispersed in ultrapure water, and ultrapure water is injected from the high-pressure nozzle. Processing method. 7. The processing method using a high-speed shear flow according to claim 1, wherein a recovery means is disposed downstream of the high-speed shear flow generated by the high-pressure nozzle to recover the processing liquid. .