Patent Application
20070298167
Various embodiments in accordance with the present invention will be described with reference to the drawings, in which:
a) and (b) illustrate, respectively, front and side views of a cooling module that can be used in accordance with one embodiment of the present invention;
a) and 4(b) illustrate, respectively, top and side views of a blower device that can be used in accordance with one embodiment of the present invention;
Systems and methods in accordance with various embodiments of the present invention can overcome the aforementioned and other deficiencies in existing curing and other radiation-utilizing applications. In one embodiment, a cooling module is used to cool a radiation source (e.g., a UV lamp), the cooling module being operable to recirculate cooling fluid (e.g., nitrogen gas) through the source so as to reduce the load on the exhaust system for the production line or fabrication facility. The recirculation of a selected fluid, as opposed to the introduction of a flow of air into the system, also can provide for the reduction and/or elimination of seal requirements from users of the system, as the amount of the selected cooling fluid leaking into the system is less critical that for water vapor and feed air, which can include higher levels of oxygen, for example. The module can use a simple heat exchanger that utilizes cooling water (such as process water or another appropriate liquid) to remove heat from the re-circulating fluid. The cooling module can utilize at least one inline blower (or other flow-inducing device) in order to generate and direct a high velocity flow of fluid (such as forced gas) to the radiation source, which can include a magnetron and UV bulb in a UV lamp module, for example. In one embodiment, pure nitrogen gas and/or nitrogen enriched air is used as the re-circulating fluid to reduce the formation of ozone formation inside the cooling system. The use of pure nitrogen gas also can reduce the amount of UV radiation (particularly at wavelengths less than 200 nm) absorbed by oxygen in the re-circulating fluid, thus increasing the UV intensity or irradiance output to the workpiece being exposed to the UV radiation. A catalyst can be used inside the recirculation system to remove any residue ozone. In one embodiment, an ozone destruction unit is embedded or otherwise integrated into the recirculation system to reduce the amount of ozone, and the corresponding consumption of purge nitrogen, for example. The return fluid is heated by the radiation source, such that no external heat input is needed for the catalyst to reach high ozone destruction efficiency.
Each lamp module 202, 204 in this embodiment has a respective blower 210, 212 positioned and operable to direct a controllable flow of cooling fluid into the respective module. The blowers can be any appropriate device operable to generate and/or direct a flow of a cooling fluid into the respective module, such as a blower operable to generate on the order of about 1400 CFM of cooling fluid per chamber. It also should be understood that it is not necessary to have one blower for each module or chamber, as a single blower, for example, could be used to provide a flow that is subsequently bifurcated and directed to separate modules and/or chambers.
The blowers 210, 212 can direct a cooling fluid from a cooling fluid supply, such as a supply plenum 214 or other (typically positive pressure) source of fluid. The supply plenum 214 can receive a flow of purge gas, such as pure nitrogen or nitrogen enhanced gas, to replace any gas lost due to leakage or consumption during the cooling and recirculation process. The supply plenum 214 also can have at least one gas sensor, such as an oxygen sensor 220 for monitoring oxygen levels in the re-circulating fluid. The blowers can direct the cooling fluid through the lamp modules 202, 204 into the respective curing chambers 206, 208, then the heated fluid can be directed through re-circulating lines 230, 232 into a return plenum 216 or other chamber or reservoir for receiving the heated fluid. A heat exchanger 218 can be positioned between the return plenum 216 and the supply plenum 214, or at least along a flow path between the return and supply plenums, so that heat can be removed from the recirculated fluid before the fluid is directed back to the lamp modules.
In one embodiment, the curing system is a UV curing system composed of one or more UV modules including but not limited to UV lamps powered by Microwave, RF, and/or DC energy sources. The UV source can be designed or selected to meet specific UV spectral distribution requirements in order to perform curing and chamber cleaning, which is achieved by using one, two, or more different types of UV lamps (e.g., low pressure Hg, medium pressure Hg, high pressure Hg, etc.) within the same array inside the chamber cavity. The chamber cavity is operable to support a heated susceptor under vacuum, where a workpiece such as a silicon wafer can be placed to receive the UV energy during a curing process.
A sufficient amount of cooling fluid is directed into the lamp modules to cool down the magnetron and UV lamp. For an exemplary DSS (Dual Sweeping Source) UV chamber, about 1400 CFM of cooling air is needed per chamber, requiring 4200 CFM of cooling air for one Producer SE system having 3 DSS Nanocure UV chambers (the Nanocure UV chambers available from Applied Materials, Inc. of Santa Clara, Calif.), This can be a very high load for a facility exhaust system, and without the re-circulating apparatus can exceed customer fabrication facility capacity.
In one embodiment shown in
a) and 4(b) show an exemplary blower 400 that can be used in such a cooling air device. This blower 400 includes a rotating fan 402 operable to direct an appropriate flow of fluid for cooling the respective UV lamp module, such as a flow of at least 7″ water gauge force air. The blower is shown to include a connector 406 and liquid-tight fitting 408, as well as a nameplate 412 and vibration damping material 410. As can be seen, the attachment points 404 are located equidistant about a periphery of the rotating fan in order to balance the blower and reduce vibration in the device. Such a blower can be, for example, model AMETEK® Rotron 041-402000 available from AMETEK® Technical & Industrial Products of Kent, Ohio.
A significant concern is that the ozone accumulation in the recirculated will exceed OSHA or other applicable standards. A recirculation system in accordance with one embodiment uses pure nitrogen as a make-up gas to mitigate this issue. A nitrogen purge gas can remove and/or reduce the oxygen concentration in the recirculation apparatus to less than about 1%. An oxygen sensor can be integrated into the recirculation system to monitor the oxygen concentration inside the re-circulating gas flow in order to ensure a proper purge of oxygen.
As discussed above, a flow of nitrogen or nitrogen enhanced gas can be used advantageously as the re-circulating cooling fluid. Due to factors such as leaks and absorption, a steady source of nitrogen is needed to supplement the supply in the cooling system. Since providing a flow of pure nitrogen can increase costs and system complexity as known in the art, the cooling fluid system can incorporate a nitrogen-producing or extracting device capable of producing a sufficient amount of nitrogen or nitrogen enhanced gas. One such device is a membrane-containing device operable to generate a flow of nitrogen from a flow of air input into an end of a tubular membrane, for example. Such a membrane 500 is shown in
The system controller 602 in
As would be apparent to one of ordinary skill in the art, the system controller can monitor various aspects of the overall system, such as the flow rate, pressures, temperatures, gas component levels, etc., by receiving signals from the appropriate sensors, and can alert operators and/or control components to adjust parameters or perform maintenance as necessary. For example, the system controller can monitor the flow rate through the cooling system, and can adjust the speed of the blowers in response thereto. Various other uses and applications of the system controller, user interface, and data storage would be apparent to one of ordinary skill in the art in light of the descriptions and suggestions contained herein.
As discussed above, the recirculation cooling system is not hermetically sealed. As such, small amounts of air (typically containing 20.9% Oxygen) may leak, or back stream, into the recirculation system. The presence of oxygen can result in the formation of trace amounts of ozone via UV irradiation, such as is given by the following formulae known in the art for atmospheric ozone formation and destruction from oxygen species:
O2+hν→2O ki(1/s)
O+O2+M→O3+M k2(cm6/(molecule2s1))
O3+hν→O+O2 k3(1/s)
O+O3→2O2 k4(cm3/(molecule1s1)),
where O is an oxygen atom, O2 is a molecule of oxygen, O3 is a molecule of ozone, hν is a photon of ultraviolet radiation, and M is any non-reactive species that can absorb the energy released in the second reaction (formation of ozone from oxygen and a third oxygen atom) to stabilize the ozone. M is not oxygen or nitrogen. Ozone is not a very stable molecule, and would tend to break back into O and O2 if M did not absorb the excess energy. The rate constants are given by k1 . . . k4.
In order to comply with regulations such as current OSHA regulations, it is desired to maintain the ozone concentration below about 0.08 ppm in various UV cooling systems. This then can require the reduction or destruction of ozone produced in the systems. An ozone destruction unit can be added to the cooling system to control the amount of ozone circulating in the system. In one embodiment, an ozone destruction unit utilizes a catalytic reaction to abate ozone, as the active ingredient will not be consumed. Further, no external heat (energy) is required for these catalytic reactions, such as are given by the following formulae:
O3+M→M-O+O2
O3+M-O→M+2O2
An ozone destruction unit in one embodiment contains a low temperature oxidation catalyst, such as Carulite® (a volatile organic compound destruction catalyst available from, and a registered trademark of, Carus Chemical Company of Peru, Ill.), PremAir® (an ozone destruction catalyst available from, and a registered trademark of, Engelhard Corporation of Iselin, N.J.), activated carbon, MnO2/CuO, MnO2/CuO/Al2O3, Pd/MnO2, or Pd/MnO2/Silica-Alumina. The catalyst can be pellet size, for example, or can be a film coated on high surface area media such as a honeycomb, radiator, etc.
An ozone destruction unit 802 can be used with any appropriate cooling and/or recirculation system, such as the exemplary UV curing and recirculation cooling system 800 illustrated in
The ozone destruction unit 802 can include, or have connected thereto, an ozone sensor 810 operable to monitor a level of ozone in the cooling system. The sensor 810 and the ozone destruction unit can be in communication with a system controller 820, which can receive a signal from the ozone sensor and monitor the ozone level in response thereto. The controller can monitor the ozone levels, and can monitor other aspects such as a remaining lifetime of the catalyst, and can generate an alert when ozone levels reach or approach unacceptable levels, or when the catalyst needs to be changed or supplemented. The alert can be sent to a user interface 822, such as a personal computer or other interface mechanism or device as known or used in the art for informing a user or operator of information about the system. The system controller and/or user interface can be in communication with a data storage device 824, such as a database storing information about the system such as the standard catalyst lifetime and maximum ozone threshold.
The unit 802 also can include a media filter in addition to, or in place of, the catalyst. A media filter can be used to remove any undesirable particulates from the re-circulating gas flow. The filter can be any appropriate filter known or used in the art for such purposes. It should be understood that a media filter also can be contained in a unit separate from the catalyst destruction unit.
Although the catalyst is shown to be a free-flowing material inside the housing in the figure, it should be understood that the catalyst can be used in any appropriate manner known or used in the art, such as coating a passageway, paths, or network that the gas passes through, in order to control the flow of gas and the level of reaction in the unit. For example, a catalyst such as PremAir® can be coated on the interior surfaces of a radiator that the gas flow passes through in the unit.
The temperature can also have an effect on the necessary residence or contact times needed for ozone destruction or abatement. Table 1 shows residence times and temperatures needed for various processes.
Many other catalysts can be used to reduce the amount of ozone in the cooling fluid. For example, activated carbon can be used to decompose ozone in nitrogen-enriched gas. Unfortunately, active carbon is consumed in the process such that a constant supply of active carbon is needed. Further, the use is limited to applications where the ozone concentration is relatively low. Using activated carbon also can present a fire danger, particularly for higher ozone concentrations or where ozone is generated from a concentrated oxygen source. Activated carbon typically is used in water treatment to remove excess ozone, and may generate carbon monoxide and carbon dioxide byproducts. Such a process also can generate particles through the ozone reaction that can flow into the system. Activated carbon reactions can follow the following formulae:
O3+C→CO+O2
O3+CO→CO2+O2
Other catalysts that have been investigated include a Carulite® low temperature oxidation catalyst (MnO2/CuO), as well as a Carulite® 200 catalyst in ozone engineering (MnO2/CuO/Al2O3).
The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims.
This application claims priority to U.S. Provisional Application No. 60/816,800, entitled “Nitrogen Enriched Cooling Air Module for UV Curing System,” filed Jun. 26, 2006, which is hereby incorporated herein by reference. This application is also related to co-pending U.S. patent application Ser. No. ______, entitled “Nitrogen Enriched Cooling Air Module for UV Curing System,” filed concurrently with this application, Attorney Docket No. A 11181/T74610, which is hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60816800 | Jun 2006 | US |
