Patent Application
20080280068
The present invention is directed to an apparatus and method for manufacturing ultra-fine particles and, more specifically, to an apparatus and method for producing ultra-fine particles of a nanometer size from reaction gases through irradiation of high energy light beams, corona discharge and formation of electric fields.
In general, ultra-fine particles of a nanometer size are produced through the use of a flame or within a furnace and then collected by means of a filter or a collecting plate. Such a conventional method has drawbacks in that a great deal of energy is consumed in the process of producing the ultra-fine particles at an elevated temperature and further that the ultra-fine particles are collected at a reduced efficiency. Another shortcoming is that the environment may be polluted by non-collected ultra-fine particles of metal oxide such as SiO2, Fe2O3 or the like. The conventional method presents a further problem in that the ultra-fine particles are adhered to one another into a lump, thus loosing its intrinsic characteristics.
Another known method of producing ultra-fine particles is a corona discharge, one kind of in-gas discharges, characterized by a phenomenon that, if a high voltage is developed between two electrodes, the portion of an electric field with high intensity emits light prior to the generation of a spark and hence becomes electrically conductive. The electric field is uniformly created in a case that the electrodes are all comprised of a plate or a sphere having an increased diameter. If one or both of the electrodes is of a needle type or a cylinder type, the portion of electric field adjacent to that electrode becomes more intensive than elsewhere, whereby a partial discharge is brought on. Electrons discharged in the corona discharge process are collided with molecules of the surrounding air, thus generating a large quantity of positively charged ions. The gases kept divided by the electrons and the positive ions are referred to as plasma.
The plasma technology to which the corona discharge belongs is extensively used in dry etching, chemical vapor deposition (CVD), plasma polymerization, surface modification, sputtering, air purification and other applications, as disclosed in U.S. Pat. Nos. 5,015,845, 5,247,842, 5,523,566 and 5,873,523.
However, the above-noted and other prior art plasma technologies pose a problem in that the apparatus used becomes structurally complicated by the adoption of a needle type or cylinder type electrode. In particular, the needle type electrode is apt to be degraded and severed when in use for a prolonged period of time. Replacing the severed electrode with a new one reduces workability and operability. Furthermore, the corona discharge has a limit in increasing the yield rate of ultra-fine particles.
In view of the above-noted problems inherent in the prior art, it is an object of the present invention to provide an apparatus and method capable of producing, with an increased yield rate, ultra-fine particles of a nanometer size from reaction gases through irradiation of high energy light beams, corona discharge and formation of electric fields.
Another object of the present invention is to provide an apparatus and method that can collect ultra-fine particles with enhanced efficiency.
A further object of the present invention is to provide an apparatus and method that can have different kinds of ultra-fine particles bonded together and can efficiently coat one ultra-fine particle on the other.
With these objects in mind, one aspect of the present invention is directed to an ultra-fine particle manufacturing apparatus comprising: a housing having a chamber and an optical window provided at one side of the chamber; a reaction gas supply means provided outside the housing for supplying reaction gases to the chamber; at least one reaction gas inlet tube mounted on an upstream side of the housing and connected to the reaction gas supply means for introducing the reaction gases into the chamber; a gas outlet tube mounted on a downstream side of the housing for discharging non-reacted gases; a high energy light source provided for irradiating high energy light beams on the reaction gases introduced into the chamber through the optical window of the housing to produce a large quantity of ultra-fine particles; a collecting means grounded and disposed at a downstream side within the chamber for collecting the ultra-fine particles; and a power supply means connected to the reaction gas inlet tube for applying a voltage to the reaction gas inlet tube.
Another aspect of the present invention is directed to an ultra-fine particle manufacturing method comprising the steps of: irradiating high energy light beams into a chamber of a housing through the use of a high energy light source; supplying reaction gases from a reaction gas supply means to a reaction gas inlet tube; introducing the reaction gases through the reaction gas inlet tube into the chamber of the housing to produce a large quantity of ultra-fine particles through the reaction of the reaction gases with the high energy light beams; applying a voltage to the reaction gas inlet tube by means of a power supply means; and collecting the ultra-fine particles flowing within the chamber of the housing by means of a collecting means.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Provided outside the housing 10 is a reaction gas supply device 20 for supplying to the chamber 12 a variety of reaction gases composed of precursors of TTIP (titanium tetraisoproxide, Ti(OC3H7)4), TEOS (tetraethoxyorthosilicate, Si(OCH2(H3)4) and the like. The reaction gas supply device 20 includes a reaction gas source containing the reaction gases, a compressor connected to the reaction gas source for pressurizing the reaction gases and a mass flow controller (MFC) for controlling flow rate of the reaction gases. The reaction gas source is comprised of a reservoir for storing the precursors, a nozzle for injecting the precursors supplied from the reservoir and a heater for heating the precursors as they are injected from the nozzle. The details of the compressor, the mass flow controller, the reservoir, the nozzle and the heater are well-known in the art and therefore will not be described herein. The reaction gases may be supplied by mixing with carrier gases, such as Ar, N2, He and so forth, stored in a reservoir of a carrier gas source.
On the upstream side of the housing 10, there is disposed a reaction gas inlet tube 30 that remains in communication with the reaction gas supply device 20 through a pipeline 22. The reaction gas inlet tube 30 has a tip end protruding into the chamber 12 such that the reaction gases can be guided toward and injected into the upstream part of the chamber 12. The reaction gas inlet tube 30 has a cross-section of varying shapes, e.g., a circular shape or a slit shape, and may be constructed from a nozzle or a capillary whose diameter is equal to or smaller than 1 mm. Connected to the downstream side of the housing 10 is a gas outlet tube 40 to which is mounted a gas discharging device 50 for forcibly discharging the non-reacted gases from the chamber 12. The gas discharging device 50 is comprised of a pump 52, i.e., an air blower, for generating a gas suction force. The non-reacted gases discharged by the gas discharging device 50 are fed to a well-known scrubber for treatment via a pipeline connected to the gas discharging device 50.
The ultra-fine particle manufacturing apparatus of the first embodiment further includes a high energy light source 60 for irradiating a high energy light beam on the reaction gases introduced into and flowing within the chamber 12 of the housing 10. The light source 60 is disposed outside the housing 10 and the light beam of the light source 60 is irradiated on the reaction gases flowing within the chamber 12 through the optical window 14 of the housing 10. The high energy light source 60 may be comprised of an X-ray generator, an ultraviolet ray generator, an infrared ray generator, a laser or the like. Irradiation of the high energy light beam causes the reaction gases to react in such a way that a myriad of ultra-fine particles P having a nanometer size can be produced.
At the downstream part of the chamber 12, there is disposed a collecting plate 70, as one example of collector means, for collecting the ultra-fine particles P produced by the irradiation of the light beam. The collecting plate 70 is spaced apart from the bottom of the chamber 12 at a predetermined interval and is grounded. A door 16 is attached to the housing 10 and can be opened to load and unload the collecting plate 70 into and out of the chamber 12. If desired, the door 16 may be replaced by a gate valve. Although
The collecting plate 70 is fabricated from, e.g., a silicon wafer, a glass substrate, a filter or the like. The method of collecting ultra-fine particles with the silicon wafer may be employed in manufacturing semiconductors, whereas the method of collecting ultra-fine particles with the glass substrate may find its application in the process of manufacturing flat panel displays such as a TFT-LCD (thin film transistor-liquid crystal display), PDP (plasma display panel) and so forth.
On the upstream end of the housing 10, there is provided a sheath gas inlet tube 80 that encloses the periphery of the reaction gas inlet tube 30 and injects into the housing 10 sheath gases such as Ar, N2 and the like. The sheath gas inlet tube 80 is connected to a sheath gas supply device 90 via a pipeline 92. Just like the reaction gas supply device 20 noted above, the sheath gas supply device 90 is comprised of a reservoir, a compressor and a mass flow controller, all of which are well-known in the art.
The sheath gases introduced into the chamber 12 of the housing 10 through the sheath gas inlet tube 80 serve to form a gas curtain 82 that encloses the reaction gas inlet tube 30 and its bottom space, as illustrated with single-dotted chain lines in
The ultra-fine particle manufacturing apparatus of the first embodiment further includes a power supply device 100 connected to the reaction gas inlet tube 30 for applying electric voltage to the reaction gas inlet tube 30. The reason for applying the electric voltage is to ensure that the ultra-fine particles P are collected with an increased efficiency by the voltage difference between the reaction gas inlet tube 30 and the collecting plate 70.
Now, an ultra-fine particle manufacturing method according to the first embodiment of the present invention will be described with reference to
Referring collectively to
The high energy light source 60 is operated to irradiate high energy light beams into the chamber 12 of the housing 10 (S14). The reaction gas supply device 20 is also operated to feed the reaction gases to the reaction gas inlet tube 30 (S16). Thus, the reaction gases are introduced into the chamber 12 of the housing 10 from the reaction gas inlet tube 30 (S18). The reaction gases introduced into the chamber 12 of the housing 10 react with the high energy light beams, thus producing a myriad of ultra-fine particles P of a nanometer size (S20). In this regard, the high energy light beams outputted from the high energy light source 60 are irradiated on the reaction gases flowing within the chamber 12 through the optical window 14 of the housing 10. As the high energy light beams are irradiated in this manner, the molecular structures of the reaction gases are changed in such a fashion that the components of the reaction gases with a low vapor pressure are condensed into the nanometer-sized ultra-fine particles P.
In an effort to examine the size distribution of the ultra-fine particles produced by the ultra-fine particle manufacturing apparatus of the first embodiment, the reaction gases made of a mixture of Fe(CO)5 and N2 were introduced into the chamber 12 of the housing 10 and soft X-rays with a wavelength of 1.2-1.5 nm were irradiated on the ultra-fine particles. The size distribution of the ultra-fine particles thus measured is graphically shown in
Subsequently, the power supply device 100 is activated to apply an electric voltage to the reaction gas inlet tube 30 (S22). As the electric voltage is applied to the reaction gas inlet tube 30, an electric field is created between the reaction gas inlet tube 30 and the collecting plate 70 and electrically charges the ultra-fine particles P (S24).
By the operation of the pump 52, the ultra-fine particles P within the chamber 12 are caused to flow toward the gas outlet tube 40 along with the non-reacted gases and the sheath gases (S26), in which process the ultra-fine particles P are collected on the top surface of the collecting plate 70 (S28). At this time, the gas curtain 82 prevents any diffusion of the ultra-fine particles P and helps the ultra-fine particles to flow in a laminar pattern, thus allowing the ultra-fine particles P to be collected on the collecting plate 70 in a facilitated manner. This inhibits the ultra-fine particles P from adhering to the inner surface of the housing 10 as they flow within the chamber 12 of the housing 10, thereby effectively avoiding any loss of the ultra-fine particles P. Moreover, the ultra-fine particles P electrically charged are accelerated within the electric field and rapidly collected on the top surface of the collecting plate 70. Finally, the non-reacted reaction gases and the sheath gases are discharged through the pump 52 to a gas scrubber for purification (S30).
The power supply device 100 is connected to the reaction gas inlet tube 30 so that it can apply a high electric voltage to the latter. The power supply device 100 serves either to apply a direct constant voltage of no smaller than 6 kv to the reaction gas inlet tube 30 as illustrated in
The ultra-fine particle manufacturing apparatus of the second embodiment further includes a cooling device 110 disposed beneath the collecting plate 70. The cooling device 110 acts to increase the ultra-fine particle collecting efficiency by cooling down the collecting plate 70. As the collecting plate 70 is cooled down under the action of the cooling device 110, the ultra-fine particles P flow smoothly from the upstream side to the downstream side of the chamber 12 by the effect of thermophoresis and then collected on the collecting plate 70. The cooling device 110 may be comprised of a coolant-circulating evaporator, a thermoelectric cooler module or other coolers known in the art. Among others, the evaporator is adapted to absorb heat from and cool down the collecting plate 70, which cooling system is useful in the case of requiring a greater cooling capacity. The thermoelectric cooler module acts to cool down the collecting plate 70 by the heat absorption and radiation of a Peltier device, which cooling system is useful in the case of requiring a smaller cooling capacity. It should be appreciated that the cooling device 110 noted above may also be employed with respect to the collecting plate 70 in the ultra-fine particle manufacturing apparatus of the first embodiment.
The power supply device 100 is connected to the reaction gas inlet tube 30 so that it can apply a high electric voltage to the latter. Application of the high voltage causes partial corona discharge to occur at the tip 32 of the reaction gas inlet tube 30, thereby creating a corona discharge zone 34. Connected to the power supply device 100 is a first voltage dropper 120 which in turn is coupled to the housing 10. The first voltage dropper 120 serves to reduce the high voltage supplied from the power supply device 100. In response, the housing 10 is supplied with a low voltage whose polarity is the same as that of the high voltage applied to the reaction gas inlet tube 30. Connected to the first voltage dropper 120 is a second voltage dropper 122 that further reduces the voltage already reduced by the first voltage dropper 120. The second voltage dropper 122 is kept grounded. In the case that the first voltage dropper 120 and the second voltage dropper 122 have the same resistance value, the voltage developed between the reaction gas inlet tube 30 and the housing 10 becomes identical to the voltage developed between the housing 10 and the ground.
As the first voltage dropper 120 and the second voltage dropper 122, a variable resistor or a fixed resistor is used capable of developing a voltage difference between the housing 10 and the reaction gas inlet tube 30. Alternatively, two power supply devices each connected to the housing 10 and the reaction gas inlet tube 30 may be employed in place of the power supply device 100, the first voltage dropper 120 and the second voltage dropper 122. In this case, one of the power supply devices serves to apply a high voltage to the reaction gas inlet tube 30 and the other of the power supply devices serves acts to apply a low voltage to the housing 10.
Below the optical window 14 and outside the housing 10, there is provided a heater 130 as a means for imparting thermal energy to the chamber 12. The thermal energy imparted by the heater 130 induces crystal growth of the ultra-fine particles P. The heater 130 may be equally employed in the ultra-fine particle manufacturing apparatuses of the first and second embodiments.
The first reaction gas inlet tube 230 is connected to the first reaction gas supply device 220 via a pipeline 222. The ultra-fine particle manufacturing apparatus of the fourth embodiment further includes a second reaction gas supply device 240 and a second reaction gas inlet tube 250. The second reaction gas inlet tube 250 is provided at one side of the outer surface of the housing 10 in between the optical window 14 and the heater 130. The second reaction gas inlet tube 250 remains in communication with the second reaction gas supply device 240 via a pipeline 242 so as to introduce therethrough the second reaction gases supplied from the second reaction gas supply device 240 into the chamber 12.
Now, an ultra-fine particle manufacturing method according to the second embodiment of the present invention will be described with reference to
Referring collectively to
The power supply device 100 is operated to apply a high voltage to the first reaction gas inlet tube 230, thereby inducing the corona discharge (S104). The power supply device 100 applies a direct constant voltage of higher intensity to the first reaction gas inlet tube 230, which high voltage is also dropped into a low voltage by the first voltage dropper 120 and then applied to the housing 10. Corona discharge occurs at the tip 232 of the first reaction gas inlet tube 230 by the high voltage supplied from the power supply device 100. The corona discharge creates a corona discharge zone 234 around the tip 232 of the first reaction gas inlet tube 230, as depicted with a broken line in
Subsequently, the first reaction gas supply device 220 is operated to supply the first reaction gases composed of, e.g., TEOS, to the first reaction gas inlet tube 230 through the pipeline 222 (S106). The first reaction gases are introduced into the chamber 12 of the housing 10 through the first reaction gas inlet tube 230 (S108). The first reaction gases supplied to the corona discharge zone 34 through the first reaction gas inlet tube 230 are decomposed by the ions and the electrons of high energy into a myriad of first nanometer-sized ultra-fine particles P1 (S110). At this time, the first reaction gases composed of TEOS is converted to the first ultra-fine particles of SiO2.
As can be seen in
Referring back to
Then, the pump 52 is operated so as to cause the first ultra-fine particles P1, the non-reacted gases and the sheath gases to flow from the chamber 12 toward the gas outlet tube 40 (S116). The second reaction gas supply device 240 is operated to supply the second reaction gases composed of, e.g., TTIP, to the second reaction gas inlet tube 250 through the pipeline 242. This allows the second reaction gases to be injected from the second reaction gas inlet tube 250 to around the first ultra-fine particles P1 flowing within the chamber 12 of the housing 10 (S118). The heater 130 is operated to apply thermal energy to the chamber 12 of the housing 10 such that the second reaction gases are subjected to thermal chemical reaction, thus producing second ultra-fine particles P2. The second ultra-fine particles P2 that have undergone the thermal chemical reaction are coated on the surface of the first ultra-fine particles P1 flowing toward the downstream side within the chamber 12 (S120). In this process, the SiO2 particles produced from the first reaction gases are coated with the TiO2 particles obtained from the second reaction gases, thereby creating TiO2-coated SiO2 particles. At this time, the ultra-fine particles P1 do not adhere to the housing 10, due to the fact that the housing 10 is applied with the low voltage whose polarity is the same as that of the high voltage applied to the first reaction gas inlet tube 230. Accordingly, it is possible to minimize the loss of the ultra-fine particles P1 and to collect them with enhanced efficiency.
In the meantime, the first ultra-fine particles P1 coated with the second ultra-fine particles P2 are collected on the collecting plate 70 (S122). The collecting plate 70 is cooled down by the operation of the cooling device 110, at which time the first ultra-fine particles P1 coated with the second ultra-fine particles P2 flow smoothly from the upstream side to the downstream side of the chamber 12 by the effect of thermophoresis and then collected on the collecting plate 70. Finally, the non-reacted first and second reaction gases and the sheath gases are discharged through the pump 52 to a gas scrubber for purification (S124).
According to the ultra-fine particle manufacturing apparatus of the fifth embodiment, if the power supply device 100 applies a high voltage to the connecting pipe 36, corona discharge occurs at the respective tips 32 of the reaction gas inlet tubes 30a-30d, thereby forming a corona discharge zone 34. This produces a greater quantity of ultra-fine particles than in the case of using a single reaction gas inlet tube. The yield rate of the ultra-fine particles is further increased as the reaction gases are uniformly introduced into the chamber 12 of the housing 10 through the reaction gas inlet tubes 30a-30d and irradiated by the light beams emitted from the high energy light source 60. The reaction gas inlet tubes 30a-30d constituting the ultra-fine particle manufacturing apparatus of the fifth embodiment may be employed in the ultra-fine particle manufacturing apparatuses of the first through fourth embodiments.
The first and second reaction gas inlet tubes 330a and 330b are mounted on one and the other sides of the housing 310 in a mutually confronting relationship and protrude into the chamber 312 of the housing 310 at their tips 332a and 332b. The first reaction gas inlet tube 330a is connected through a pipeline 322a to the first reaction gas supply device 320a that serves to supply first reaction gases to the chamber 312 of the housing 310. The second reaction gas inlet tube 330b is connected through a pipeline 322b to the second reaction gas supply device 320b that serves to supply second reaction gases differing from the first reaction gases to the chamber 312 of the housing 310.
Furthermore, the gas outlet tube 340 is connected to the lower center part of the housing 310 and centrally aligned between the first reaction gas inlet tube 330a and the second reaction gas inlet tube 330b. The gas discharging device 350 has a pump 352 mounted at the downstream end of the gas outlet tube 340. The collecting plate 370 is loaded into and unloaded from the gas outlet tube 340 through a door 342 and remains grounded. First and second optical windows 314a and 314b are respectively provided on the lower opposite sides of the housing 310. Through the first and second optical windows 314a and 314b, the first and second high energy light sources 360a and 360b irradiate high energy light beams on the first and second reaction gases introduced into the chamber 312 of the housing 310.
The first and second power supply devices 380a and 380b are adapted to apply high voltages of opposite polarities to the first reaction gas inlet tube 330a and the second reaction gas inlet tube 330b, respectively, so that corona discharge occurs at the tip 332a of the first reaction gas inlet tube 330a and the tip 332b of the second reaction gas inlet tube 330b. For example, the first power supply device 380a applies a high voltage of a positive polarity to the first reaction gas inlet tube 330a but the second power supply device 380b applies a high voltage of a negative polarity to the second reaction gas inlet tube 330b.
The first and second reaction gas supply devices 320a and 320b serve to supply the first and second reaction gases of different kinds to the first reaction gas inlet tube 330a and the second reaction gas inlet tube 330b through the pipelines 322a and the 322b. The first ultra-fine particles P1 flowing through the corona discharge zone 334a of the first reaction gas inlet tube 330a are positively charged, while the second ultra-fine particles P2 flowing through the corona discharge zone 334b of the second reaction gas inlet tube 330b are negatively charged. The positively charged first ultra-fine particles P1 and the negatively charged second ultra-fine particles P2 are bonded to each other at the midway area between the first reaction gas inlet tube 330a and the second reaction gas inlet tube 330b. This makes it possible to obtain an ultra-fine particle mixture in which the first ultra-fine particles P1 are admixed with the second ultra-fine particles P2 at a predetermined ratio.
One of the first and second reaction gas inlet tubes 330a and 330b, for example, the second reaction gas inlet tube 330b, may be grounded and the second power supply device 380b may be eliminated it its entirety. In this case, if the first power supply device 380a applies a high voltage to the first reaction gas inlet tube 330a, a high potential difference is developed between the first reaction gas inlet tube 330a and the second reaction gas inlet tube 330b such that corona discharge can occur at the tip 332a of the first reaction gas inlet tube 330a and the tip 332b of the second reaction gas inlet tube 330b.
The ultra-fine particle manufacturing apparatus of the sixth embodiment further includes a carrier gas supply device 390 and a carrier gas inlet tube 392. The carrier gas supply device 390 serves to supply carrier gases, such as Ar, N2, He or the like, to thereby assure smooth flow of the first ultra-fine particles P1, the second ultra-fine particles P2 and the mixture thereof. The carrier gas inlet tube 392 is mounted on the top of the housing 310 in an alignment with the gas outlet tube 340 and communicates with the carrier gas supply device 390 through a pipe line 394. The carrier gases are supplied to the carrier gas inlet tube 392 by the operation of the carrier gas supply device 390 and then introduced into the upstream end of the chamber 312. The carrier gases flow downwardly from the upstream side of the chamber 312, thus leading the ultra-fine particle mixture to the gas outlet tube 340. Accordingly, the ultra-fine particle mixture is collected on the top surface of the collecting plate 370 with increased efficiency.
Although a variety of preferred embodiments of the present invention have been described for the illustrative purpose only, it will be apparent to those skilled in the art that the present invention is not restricted to the illustrated embodiments but various changes or modifications may be made thereto within the scope of the invention defined by the appended claims.
As described in the foregoing, according to the ultra-fine particle manufacturing apparatus and method of the present invention, it is possible to produce, with an increased yield rate and collection efficiency, ultra-fine particles of a nanometer size from varying kinds of reaction gases through irradiation of high energy light beams, corona discharge and formation of electric fields. Also possible is to have different kinds of ultra-fine particles bonded together and to efficiently coat one kind of ultra-fine particles on the other, thereby producing new kinds of ultra-fine particles in an easy and efficient manner.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2005-0022178 | Mar 2005 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR2006/000911 | 3/14/2006 | WO | 00 | 7/15/2008 |
