JPS61220763A - Method for controlling speed of fine particle flow - Google Patents

Abstract

PURPOSE:To transfer under accurate control of supersonic speed by regulating the ratio of pressures on the upstream and the downstream side of a contracting and expanding nozzle provided at the flow passage to less than the ratio of the critical pressures. CONSTITUTION:The ratio of the pressures on the upstream and the downstream side of a contracting and expanding nozzle 1 is regulated to less than the ratio of the respective critical pressures. Consequently, since fine particles can be transferred independently in the space as a supersonic beam of uniformly dispersed fine particles, the fine particles can be transferred under accurate control of supersonic speed. Accordingly, the active fine particles can be transferred to a collecting position under such conditions and the kinetic energy when the particles are blown can be precisely controlled.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a method for controlling the speed of a particle flow used in the transportation and spraying of particles, for example, in film-forming processing, composite processing, etc. using particles. It is expected that it will be applied to the formation of materials, doping processing, and new formation sites for fine particles.

In this specification, fine particles refer to one atomic molecule, ultrafine particles, and general fine particles. Here, ultrafine particles are 1. For example,
Evaporation method in gas, plasma evaporation method using gas phase reaction,
Obtained by gas phase chemical reaction method, colloidal precipitation method, solution spray pyrolysis method, etc. using liquid phase reaction,
Refers to ultrafine (generally 0.51 Lm or less) particles. General fine particles are 4I! A beam is a jet stream whose cross-sectional area is approximately constant in the flow direction, and its cross-sectional shape does not matter. It is.

[Prior Art] Generally, fine particles are dispersed and suspended in a carrier gas and transported by the flow of the carrier gas.

Conventionally, the speed control of the particle flow accompanying the transport of the particles is
This is simply done by dividing the entire flow path of the particles flowing together with the carrier gas using a tube or a housing, and adjusting the differential pressure between the upstream and downstream sides of the divided flow path.

Furthermore, when spraying fine particles onto a substrate, the fine particles are jetted out together with a carrier gas through a nozzle. The nozzle used to spray these particles is a simple parallel tube or tapered nozzle, and even in this case, the speed of the ejected particle flow is simply controlled by adjusting the differential pressure before and after the nozzle. .

[Problems to be Solved by the Invention] However, in the conventional flow rate control based on a mere differential pressure, the flow of particles becomes a diffusion flow with a large density distribution, making it difficult to accurately control the flow rate of the entire flow. Furthermore, in control based on differential pressure, the magnitude of the differential pressure does not necessarily lead to the magnitude of the flow velocity, and from this point of view as well, it is difficult to accurately control the flow velocity. If the flow rate cannot be controlled accurately, for example, when transporting active particles, the activity of the particles may disappear due to a delay in the transfer, or the kinetic energy of the particles may sometimes be too large. If it is too small, film formation by spraying, etc. is likely to be inhibited.

[Means for Solving the Problems] The measures taken to solve the above problems are explained with reference to FIG. 1, which is an explanatory diagram of the basic principle of the present invention. The above-mentioned problems are solved by providing a method for controlling the speed of the particle flow in which the pressure ratio between the upstream side and the downstream side of the nozzle 1 is made equal to or less than the critical pressure ratio to control the speed of the particle flow.

The contraction/expansion nozzle 1 in the present invention is a throat portion 2 in which the opening area is gradually narrowed from the inlet 1a toward the middle portion, and the opening area is gradually expanded from the throat portion 2 toward the outlet 1b. This refers to the nozzle that is In Figure 1,
For convenience of explanation, the inflow side and outflow side of the contraction/expansion nozzle 1 are as follows.
It is connected to an upstream chamber 3 and a downstream chamber 4, each of which is a closed system. However, in the present invention, the inflow side and the outflow side of the contraction/expansion nozzle l can be either a closed system or an open system, as long as a pressure ratio is created between the two and the particles can flow together with the carrier gas. Good too.

[Function] For example, as shown in FIG.
When the inside is evacuated by the vacuum pump 5, the pressure ratio P/Po between the pressure Po of the upstream chamber 3 and the pressure P of the downstream chamber 4 is set to be equal to or lower than a required critical pressure ratio. The supplied carrier gas containing fine particles is
Due to the differential pressure caused by this exhaust gas, the air flows from the upstream chamber 3 through the contraction/expansion nozzle l and into the downstream chamber 4 .

By the way, the contraction/expansion nozzle l functions not only to eject fine particles together with the carrier gas according to the pressure difference between the upstream side and the downstream side, but also to equalize the flow of the ejected carrier gas and fine particles. Therefore, by creating this uniform flow of fine particles, the overall flow velocity can be easily controlled.

In addition, when the pressure ratio P/PG in the upstream chamber 3 and downstream chamber 4 is below the critical pressure ratio, the contraction/expansion nozzle 1 is configured such that the ratio of the opening area A'' of the throat portion 2 to the opening area A of the outlet port !b is By adjusting A/A'', the flow velocity of the particles ejected together with the carrier gas can be adjusted at supersonic speeds.

Here, the velocity of the particle flow is U, and the sound velocity at that point is a.
, the specific heat ratio of the particulate flow is γ, and assuming that the particulate flow is a compressible one-dimensional flow and expands adiabatically, the Matzuha number M reached by the particulate flow is given by the following equation from the pressure Po in the upstream chamber and the pressure P in the downstream chamber. It is determined by the formula, especially when P/PG is below the critical pressure ratio, 1M
is 1 or more.

Note that the sound velocity a can be determined by the following equation, where T is the local temperature and R is the gas constant.

a = r
” and Matsuha's number M have the following relationship.

Therefore, the opening area ratio A/A'' can be determined according to the Matsuha number M determined from equation (1) by the pressure ratio P/PG of the pressure PG in the upstream chamber 3 and the pressure P in the downstream chamber 4, or by A/A''. By adjusting P/P according to M determined from equation (2), the flow velocity of the particulate flow ejected from the expansion/contraction nozzle l can be controlled at supersonic speed. The velocity U of the particle flow at this time can be determined by the first-order equation (3).

. 2M et al. 1.1. -1M2 F , -(3) On the other hand, if the fine particles are ejected in a fixed direction together with the carrier gas as a supersonic flow as described above.

The carrier gas and fine particles travel straight while maintaining almost the jet cross section immediately after being ejected, and are turned into a beam. Therefore, the flow of particles carried by this carrier gas is also converted into a beam, which moves through the space within the downstream chamber 4 with minimal diffusion, in a spatially independent state without interference with the wall surface of the downstream chamber 4, and at supersonic speeds. The speed control is therefore extremely accurate.

For this reason, it is possible, for example, to form active particles in the upstream chamber 3 and transfer them directly into a beam through the contraction/expansion nozzle 1, or to activate them within the contraction/expansion nozzle 1 or immediately after the contraction/expansion nozzle 1. If fine particles having a The particles can be collected on the substrate 6 in a good active state. Furthermore, the particles are sprayed onto the substrate 6 as a beam with a controlled flow rate.

This spraying allows the kinetic energy of the fine particles to be easily controlled.

[Example] Figure 2 is a schematic diagram of an example in which the method of the present invention is used to form a film using ultrafine particles.
3 is an upstream chamber, 4a is a first downstream chamber, and 4b is a second downstream chamber.

The upstream chamber 3 and the first downstream chamber 4a are configured as an integrated unit, and the first downstream chamber 4a is equipped with a skimmer 7, a gate valve 8, and a second downstream chamber 4, which are also each unitized.
b are sequentially connected to each other so as to be connectable and separable via flanges having a common diameter (hereinafter referred to as "common flanges"). Upstream chamber 3, first downstream chamber 4a, and second downstream chamber 4
b is maintained at a high degree of vacuum in stages from the upstream chamber 3 to the second downstream chamber 4b by an exhaust system to be described later.

A gas phase excitation device 9 is attached to one side of the upstream chamber 3 via a common flange. This gas phase excitation device 9 generates active ultrafine particles using plasma, and sends out the ultrafine particles together with a carrier gas such as hydrogen, helium, argon, nitrogen, etc. to a contraction/expansion nozzle l located on the opposite side. It is. In order to prevent the formed ultrafine particles from adhering to the inner surface of the upstream chamber 3, adhesion prevention treatment may be applied to the inner surface.
Since the first downstream chamber 4a has a higher degree of vacuum than the upstream chamber 3, the pressure difference between the two causes the carrier gas to flow directly through the contraction/expansion nozzle l and into the first downstream chamber 4a. It turns out.

As shown in FIG. 3(a), the gas phase excitation device 9 includes a rod-shaped first electrode 9a disposed within a tubular second electrode 9b, and a carrier gas and a raw material gas supplied into the second electrode ab. Thus, a discharge is caused between both electrodes 9a and 9b. Further, the gas phase excitation device 9, as shown in FIG. 3(b),
The first electrode 8a provided in the second electrode 9b may be a porous tube to supply carrier gas and raw material gas between the electrodes 9a and eb through the inside of the first electrode sa, or the same (C) may be used. As shown, both half-tubular electrodes 9a, 9
b are joined in a tubular shape via an insulating material 9C, and both electrodes 9a,
It is also possible to supply the carrier gas and source gas into the tube formed by 13b.

The contraction/expansion nozzle 1 has an inlet 1a opened in the upstream chamber 3 at the side end of the first downstream chamber 4a on the upstream chamber 3 side, and the first downstream chamber 4
It is attached via a common flange with an outlet tb opened at a and protruding into the upstream chamber 3. However, this contraction/expansion nozzle l may be installed in a state where it projects into the first downstream chamber 4a.The direction in which the contraction/expansion nozzle l should be projected depends on the size, amount, nature, etc. of the ultrafine particles to be transported. You can choose accordingly.

As mentioned above, the contraction/expansion nozzle 1 has an inlet port 1a.
It is sufficient if the opening area is gradually narrowed down to form the throat part 2, and then the opening area is gradually expanded again to form the outflow port 1b, which is shown enlarged in Fig. 4(a). As such, it is preferable that the inner circumferential surface near the outlet lb is substantially parallel to the central axis. This is because the flow direction of the jetted carrier gas and ultrafine particles is affected to some extent by the direction of the inner circumferential surface near the outlet lb, so the flow is made as parallel as possible to facilitate speed control.

However, as shown in FIG. 4(b), the angle α of the inner circumferential surface extending from the throat portion 2 to the outlet 1b with respect to the central axis is 7.
If the angle is preferably 5° or less, peeling phenomenon will not easily occur and the flow of the ejected carrier gas and ultrafine particles will be maintained almost uniformly. By omitting the formation of the part, it becomes easy to manufacture the contraction/expansion nozzle l. Furthermore, if the contraction/expansion nozzle l is made rectangular as shown in FIG. 4(C), carrier gas and ultrafine particles can be ejected in a slit shape.

Here, the above-mentioned separation phenomenon means that when there is a protrusion or the like on the inner surface of the contraction/expansion nozzle 1, the boundary layer between the inner surface of the contraction/expansion nozzle 1 and the flowing fluid becomes large.

This refers to a phenomenon in which the flow becomes non-uniform, and the higher the speed of the jet flow, the more likely it is to occur.In order to prevent this separation phenomenon, it is preferable that the above-mentioned angle α be made smaller as the inner surface finishing precision of the contraction-expansion nozzle 1 is inferior. . The inner surface of the contraction/expansion nozzle 1 has three or more, preferably four or more, inverted triangular marks representing surface finish accuracy as defined in JIS 80601. In particular, since the peeling phenomenon in the enlarged part of the contraction/expansion nozzle 1 greatly affects the subsequent flow of the carrier gas and ultrafine particles, by determining the finishing accuracy with emphasis on this enlarged part, it is possible to
can be easily produced. Further, in order to prevent the occurrence of a peeling phenomenon, the throat portion 2 needs to have a smooth curved surface so that the differential coefficient in the rate of change in cross-sectional area does not become (1).

The material for the contraction/expansion nozzle l can be widely used, such as iron, stainless steel, and other metals, as well as acrylic resin, polyvinyl chloride, synthetic resins such as polyethylene, polystyrene, and polypropylene, ceramic materials, quartz, and glass. . This material may be selected in consideration of non-reactivity with the generated ultrafine particles, processability, gas release properties in a vacuum system, etc. Also, the reduction/expansion nozzle 1
The inner surface may be coated with a material that is less likely to cause adhesion or reaction of ultrafine particles. Specific examples include polyfluoroethylene coating.

The length of the contraction/expansion nozzle l can be arbitrarily determined depending on the size of the apparatus and the like. By the way, the contraction/expansion nozzle l
When flowing through the carrier gas and the ultrafine particles, the thermal energy they possess is converted into M kinetic energy. Particularly when ejected at supersonic speed, the thermal energy becomes significantly small, resulting in a supercooled state. Therefore, if the carrier gas contains condensed components, it is also possible to actively condense them by the supercooled state, thereby forming ultrafine particles. Since the formation of ultrafine particles by this is homogeneous nucleation, it is easy to obtain homogeneous ultrafine particles. Further, in this case, in order to perform sufficient condensation, it is preferable that the contraction/expansion nozzle l be long. On the other hand, when condensation occurs as described above, thermal energy increases and velocity energy decreases. Therefore, in order to maintain high-speed jetting, it is preferable that the contraction/expansion nozzle l be short.

Pressure P in upstream chamber 3. Based on the pressure ratio P/PG below the critical pressure of the pressure P in the downstream chamber 4, the ratio A/A'' between the opening area A◆ of the throat portion 2 and the opening area A of the outflow port 1b is adjusted as appropriate. , by flowing through the contraction/expansion nozzle l,
The carrier gas containing ultrafine particles is made into a beam and flows from the first downstream chamber 4a to the second downstream chamber 4b at a supersonic speed determined by the pressure ratios P/Po and A/A''.

The skimmer 7 is installed in the first downstream chamber 4a so that the second downstream chamber 4b can maintain a sufficiently higher degree of vacuum than the first downstream chamber 4a.
This is to enable adjustment of the opening area between the first downstream chamber 4b and the second downstream chamber 4b. Specifically, as shown in FIG. 5, two adjustment plates 11 and 11' each having a dogleg-shaped notch 10 and 10' can be slid past each other with their notches 10 and 10' facing each other. It has been established in This adjustment plate 11° 11' can be slid from the outside, and the overlapping condition of both cutout portions 10.10'' can allow the passage of the beam and maintain a sufficient degree of vacuum in the second downstream chamber. The opening degree is adjusted.The shape of the notch 10.10' and the adjustment plate 11.11' of the skimmer 7 may be semicircular or other shapes other than the shape shown in FIG.

The gate valve 8 has an annular valve body 13 that is raised and lowered by turning a handle 12, and is opened when the beam is traveling. By closing this gate valve 8, the unit in the second downstream chamber 4b can be replaced while maintaining the degree of vacuum in the upstream chamber 3 and the first downstream chamber 4a. In addition, in the apparatus of this embodiment, ultrafine particles are collected in the second downstream chamber 4b, but if the gate valve 8 is a pole valve or the like, especially when the ultrafine particles are metal particles that are easily oxidized, By replacing the unit of the second downstream chamber 4b together with this Pall valve, there is an advantage that the unit can be replaced without the risk of rapid oxidation.

A base body 6 is located in the second downstream chamber 4b for receiving and depositing ultrafine particles transferred as a beam, and collecting the ultrafine particles in a film-formed state. This base body 6 is attached to the second downstream chamber 4b via a common flange, and is attached to the cylinder 1.
4 is attached to a base holder 18 at the tip of a slide shaft 15 that is slid by a slide shaft 15. A shutter 17 is located on the front side of the base 6, so that the beam can be blocked whenever necessary. Moreover, the substrate holder 16 is.

The substrate 6 can be heated or cooled under optimal temperature conditions for collecting ultrafine particles.

Incidentally, glass windows 18 are attached to the upper and lower sides of the upstream chamber 3 and the second downstream chamber 4b through common flanges, respectively, as shown in the figure, so that the inside can be observed. Although not shown, the upstream chamber 3 and the first downstream chamber 4a
Similar glass windows (similar to 18 in the figure) are also installed at the front and rear of the second downstream chamber via common flanges. These glass windows 18 can be removed and replaced with various measuring devices, load lock chambers, etc. via a common flange.

Next, the exhaust system in this embodiment will be explained.

The upstream chamber 3 is connected to a main valve 20 via a pressure regulating valve 19.
connected to a. The first downstream chamber 4a is directly connected to a main valve 20a, and this main valve 20a is connected to a vacuum pump 5a. The second downstream chamber 4b is connected to a main valve 20b, which in turn is connected to a vacuum pump 5b. Furthermore, 2
1a and 21b are main valves 20a and 20b, respectively.
The auxiliary valve 23a is connected to the immediate upstream side of the auxiliary valve 22a and 22b.

The vacuum pump 23b is connected to the vacuum pump 5a and is used to check the inside of the upstream chamber 3, the first downstream chamber 4a, and the second downstream chamber 4b. In addition, 24a-24h are each chamber 3, 4a, 4b and pump 5a, 5b, 21
a, 21b are leak and purge valves.

First, the interference valves 21a and 21b and the pressure regulating valve 1
8, the upstream chamber 3, the first and second downstream chambers 4a, 4
The checking in b is performed using the vacuum pumps 20a and 20b.

Next, the auxiliary valves 23a, 23b and the main valves 20a, 2 are closed.
0b is opened, and the upstream chamber 3. A sufficient degree of vacuum is created in the first and second downstream chambers 4a and 4b. At this time, by adjusting the opening degree of the pressure regulating valve 13, the degree of vacuum in the first downstream chamber 4a is made higher than that in the upstream chamber 3,
Next, the carrier gas and the raw material gas are flowed, and the skimmer 7 is used to adjust the degree of vacuum in the second downstream chamber 4b to be higher than that in the first downstream chamber 4a. This adjustment can also be performed by adjusting the opening degree of the main valve 20b. The chambers 3, 4a, and 4b are controlled to maintain a constant degree of vacuum throughout the formation of ultrafine particles and the film forming operation by beam injection. This control may be done manually, but each room 3, 4a,
Alternatively, the pressure inside the pump 4b may be detected, and the pressure regulating valve 18, the main valves 20a, 20b, the skimmer 7, etc. may be automatically opened and closed based on the detected pressure.

The degree of vacuum may be controlled by separately providing vacuum pumps 5a for the upstream chamber 3 and the first downstream chamber 4a for each chamber 3, 4a. However, as in this embodiment, one vacuum pump 5a is used to exhaust air in the direction of beam flow, and the upstream chamber 3
By controlling the degree of vacuum in the first downstream chamber 4a, it is easy to maintain a constant pressure ratio between the two even if there is some pulsation in the vacuum pump 5a. Therefore, there is an advantage that it is easy to maintain a constant flow state that is susceptible to fluctuations in the pressure ratio.

The suction by the vacuum pumps 5a, 5b is preferably performed from above, especially in the first and second downstream chambers 4a, 4b.By suctioning from above, the descent of the beam due to gravity can be suppressed to some extent. can.

Although the apparatus according to this embodiment is as described above, the following modifications can be made.

First, the contraction/expansion nozzle l can be tilted vertically and horizontally, and can be scanned at regular intervals, so that film formation can be performed over a wide range. Particularly, this tilting and scanning is advantageous when combined with the rectangular nozzle shown in FIG. 4(C).

The contraction/expansion nozzle 1 is made of an insulator such as quartz, and microwaves are applied thereto to form active ultrafine particles inside the contraction/expansion nozzle 1. Alternatively, the contraction/expansion nozzle 1 is made of a translucent material to generate ultraviolet, infrared, or laser radiation. It is also possible to irradiate the flow with light having various wavelengths, such as light. It is also possible to provide a plurality of contraction/expansion nozzles 1 to generate a plurality of beams at once. In particular, when a plurality of contraction/expansion nozzles l are provided, by connecting each to an independent upstream chamber 3, beams of different particles can be run at the same time. It is also possible to form new particles by collision of different particles by crossing them.

The base body 6 is held movably or rotatably in the vertical and horizontal directions,
It is also possible to receive the beam over a wide range. Further, by winding up the base body 6 into a roll and sending it out one after another so as to receive the beam, a long base body 6 can also be treated with fine particles. Furthermore.

The treatment with fine particles may be performed while rotating the drum-shaped base 6.

In this embodiment, generation chamber 3. Although it is composed of a first downstream chamber 4a and a second downstream chamber 4b, the second downstream chamber 4b may be omitted, or a third downstream chamber may be provided downstream of the second downstream chamber.

Fourth...downstream chambers can also be connected. Further, by pressurizing the upstream chamber 3, the first downstream chamber 4a can be made into an open system, and by reducing the pressure in the first downstream chamber 4a, the upstream chamber 3 can be made into an open system. In particular, like an autoclave, the upstream chamber 3 can be pressurized and the first downstream chamber 4a and below can be depressurized.

In this embodiment, active ultrafine particles are formed in the upstream chamber 3, but this is not necessarily necessary, and separately formed particles may be sent to the upstream chamber 3 together with the carrier gas. It is also possible to obtain fine particles by providing a valve that opens and closes the valve 1 and intermittently opening and closing the valve while temporarily storing the fine particles in the upstream chamber 3 side. If the valve is opened and closed in synchronization with energy application on the downstream side including the throat part 2 of the contraction/expansion nozzle l, the load on the exhaust system can be significantly reduced, and the pulse can be maintained while effectively utilizing the raw material gas. It is possible to obtain a particle flow of . Note that under the same exhaust conditions, the above-mentioned intermittent opening and closing has the advantage that it is easier to maintain a high vacuum on the downstream side. In case of intermittent opening and closing,
A chamber for temporarily storing fine particles may be provided between the upstream chamber 3 and the contraction/expansion nozzle l.

In addition, a plurality of contraction/expansion nozzles 1 are arranged in series, and the pressure ratio on the upstream side and the downstream side is adjusted respectively.

It is also possible to maintain the beam speed or make each chamber spherical to prevent dead spaces as much as possible.

[Effects of the Invention] According to the present invention, fine particles can be transported in a spatially independent state as a uniformly dispersed supersonic beam, so that fine particles can be transported under precise supersonic velocity control. be able to. Therefore, the active particles can be reliably transported as they are to the collection position, and the kinetic energy of the spraying can be accurately controlled. In addition, it becomes a focused ultra-high-speed parallel flow called a beam, and when it is made into a beam, thermal energy is converted to kinetic energy, and the particles in the beam become frozen, so we can create a new reaction field that utilizes these. I have high hopes for what I will achieve. Furthermore, according to the speed control method of the present invention, since the fluid is in the frozen state, it is also possible to define the microscopic state of molecules in the fluid and handle the transition from one state to another state. In other words, it is possible to perform chemical reactions in the gas phase using a new method in which various energy levels of one molecule are defined and energy corresponding to the levels is imparted. Furthermore, by providing a field for energy exchange different from conventional ones, it is also possible to easily create intermolecular compounds formed by relatively weak intermolecular forces such as hydrogen bonds and van der Waals bonds.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the basic principle of the present invention, Fig. 2 is a schematic diagram showing an example of applying the method of the present invention to film formation using ultrafine particles, and Fig. 3 (a) to (C). 4A to 4C are diagrams each showing an example of the shape of a contraction/expansion nozzle, and FIG. 5 is an explanatory diagram of a skimmer. l: contraction/expansion nozzle, 1a: inlet, lb: outlet, 2: throat, 3: upstream chamber, 4: downstream chamber,
4a: first downstream chamber, 4b: second downstream chamber, 5.5a, 5b: vacuum pump,
6: Substrate, 7: Skimmer, 8: Gate valve, 9: Gas phase excitation device, 8a: First electrode. 9b: second electrode, 10.10': notch, 11, 11
': Adjustment plate, 12: Handle, 13: Valve body, 14 Niji cylinder, 15 Niji slide shaft, 16: Base holder,! ? = shutter. 18 Ni-glass window, 18: Pressure adjustment valve, 20a, 20b: Main valve, 21a, 21b: Decompression pump, 22a, 22b: Arabiki valve, 23a, 23b: Auxiliary valve, 24a to 24h: Leak and purge valve.

Claims (1)

[Claims] 1) A method for controlling the speed of a particulate flow, which comprises providing a contraction/expansion nozzle in a flow path, and controlling the speed of the particulate flow by making the pressure ratio between the upstream side and the downstream side of this nozzle equal to or less than a critical pressure ratio.