The systems disclosed herein allow for automatic loading and unloading of batches of powder for treatment using chemical vapor deposition (CVD) or other processing. The present systems increase throughput and reduce the risk of exposure to hazardous gases.
Powder processing may be done in a rotary drum reactor. Many types of powder processing require a near-vacuum environment and/or high temperature. As batches of powder are sequentially inserted/removed from the reactor, the reactor conditions must be set up for the next transition. These reactor conditions include heating up, cooling down, evacuating, and backfilling with inert or process gases, etc. The time to set up these conditions increases total cycle time and reduces efficiency/throughput.
It is desirable to substantially maintain conditions inside the reactor as batches of powder are sequentially placed therein, thereby increasing product yield and reducing contamination of the reactor.
Barrels, pre-loaded with powder substrate material for treatment (e.g., coating), can be automatically loaded from one of a first or second station of a dual load lock chamber into a process chamber. The process chamber may be kept at treatment temperature at all times to increase throughput, requiring no heat up or cool down time.
As the treatment process is finishing on the powder in the currently in-process barrel that was loaded from the first station of the dual load lock chamber, the next powder-containing barrel to be processed may be placed within the second station of the dual load lock chamber, where it is primed, and readied to be loaded from the second station of the load lock chamber into the process chamber. The load lock chamber may be evacuated, and inert gas backfilled (one or several times) to ensure an inert environment prior to opening the process chamber to the load lock chamber. This may be particularly advantageous when the powder to be processed is susceptible to oxidation or corrosion in air, where the process gases that may still be present after a coating run are reactive with air, or where the coated powder within the process chamber is susceptible to oxidation or corrosion with air. Under evacuation, or non-uniform/turbulent backfill, the powder in the barrel(s) that reside in the load lock chamber may be disturbed, potentially leading to elutriation loss (powder carry-over, entrainment). Particles in the powder bed can be secured within the barrels via centrifugal confinement as described, for example, in U.S. Provisional Patent Application No. 63/312,851 filed Feb. 23, 2022 (“the '851 application”), the contents of which are incorporated herein in their entirety by this reference. Alternatively or in addition, an automatically inserted/removed plug can prevent powder loss from the barrels in the load lock chamber during evacuation or non-uniform/turbulent backfill. The plug(s) may be automatically removed when the load lock chamber and process chamber have reached their desired transfer pressure (the steady state pressure at which the barrels are loaded into, or removed from, the process chamber).
Hazardous gases are shut off, and the process chamber is purged and/or evacuated to remove residual hazardous gases therefrom prior to opening.
The fully processed barrel may be automatically unloaded from the process chamber into the unoccupied station of the dual load lock chamber. During the unload operation, the pressure differential between the process chamber and the load lock chamber is minimized in order to avoid or substantially reduce disruption to the powder bed. Alternatively, particles in the powder may be secured via centrifugal confinement while being moved to and stored within the load lock chamber.
The transfer of the barrel from the process chamber to the load lock chamber, or from the load lock chamber to the process chamber, can be performed at atmospheric pressure, sub-atmospheric pressure, or above atmospheric pressure.
An automatic mechanism may be used to swap the barrels, so that the fully processed barrel is now in the first station of the load lock chamber and the unprocessed barrel is in the second station.
The unprocessed barrel residing in the second station of the load lock chamber may be automatically loaded into the process chamber.
An end cap seal may translate on the same assembly as the unprocessed barrel and seal the process chamber from the atmosphere of the load lock chamber.
The process pressure with the sealed process chamber may be atmospheric pressure, sub-atmospheric pressure, or above atmospheric pressure.
In order to allow for rotation of the barrels, as well as loading/unloading from each station of the load lock chamber, the barrels either:
The first station of the load lock chamber is a holding bay for the barrel that allows for either pre-heat up to process temperature (or some intermediate temperature) prior to loading into the process chamber, or for cooldown prior to offloading from the load lock chamber.
The second station of the load lock chamber is an assembly with linear translation capability that moves the barrel into and out of the process chamber.
A gate valve (such as, for example, a vacuum valve) isolates the process chamber from the load lock chamber whenever the end cap is fully retracted.
The previously processed barrel may be allowed to cool in an inert atmosphere while in the first station of the load lock chamber. This occurs while the next barrel is in process, resulting in increased throughput.
A mechanism within the load lock chamber can accept a barrel ready to process, park it in an idle location, remove the completed barrel from the process chamber, park the completed barrel for cooling off, and insert the new barrel into the process chamber, all automatically via a combination of rotary, linear, and latching mechanisms.
The load lock chamber may have a heater, so that the next barrel to be loaded into the process chamber can be preheated up to the temperature of the process chamber (or some intermediate temperature) while the barrel in the process chamber is currently in process. This reduces the heat up time for the next barrel when it is loaded into the process chamber, further increasing throughput of the system.
The present systems may be operated in a manner that provides centrifugal confinement of the powder within the barrel to avoid or substantially reduce powder elutriation loss (powder carry-over, entrainment). See, the '851 application.
In embodiments, systems in accordance with the present disclosure have a fixed gas injector, thermocouple, exhaust, and rotation feedthrough/coupling. These can be cantilevered from the load end of the process chamber, or from the opposite end, or a combination. The barrels can slide over hardware that is cantilevered from either end of the process chamber during load/unload. In embodiments, the present systems include a fixed injector and exhaust at the same end of the process chamber without concern for interference with a filter element, for example, as shown in the '851 application. Centrifugal confinement (see the '851 application) mitigates particle elutriation losses so that the automatically loaded barrel designs in accordance with this disclosure can be simplified and made to be more robust by allowing for fixed injection and exhaust (rather than some mating coupling or more complex gas routing design that may be more susceptible to leaks or particulate contamination).
A fixed gas injector, aligned with the center axis of the barrel, injects the process gases for the powder treatment process. In embodiments, the injection holes are pointing upwards (against gravity) such that the process gases are directed into the dispersed particles as they fall from the top of the rotating barrel in a cataracting motion. Such injector design promotes treatment uniformity on the individual particles that form the powder.
A comb with retractable tines may be incorporated (see the '851 application). This retractable comb is designed to be compatible with the automatically loaded and unloaded barrels. In one embodiment, the comb (that is cantilevered from one end of the process chamber) engages with and retracts from the particle bed via rotary motion. In another embodiment, the pivoting comb is weighted so that in the cataracting condition, the comb engages with the particle bed and in the centrifuging condition the force due to increased angular momentum of the powder bed pushes the comb out of the way allowing the particles to centrifuge. The mechanism can be a weight, a spring, or some other force. In another embodiment, the comb has pneumatically actuated tines that engage and disengage with the powder bed.
Barrels may be on axis with rotation (concentric), or rotation may be off-axis (eccentric) to increase the centrifugal force on the powders for centrifugal confinement. Off-axis (eccentric) rotation may also help for gas injection and uniform treatment of powders.
The system may have a horizontal orientation, and a linear drive mechanism employed to load and unload the barrels from the room to the load lock chamber, and from the load lock chamber to the process chamber.
The load lock chamber may also interface with multiple process chambers for parallel processing, to further increase throughput.
The present disclosure may be understood by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which:
Embodiments of the presently disclosed powder treatment systems are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.
Reference is made in detail to specific embodiments, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation, not limitation. It will be apparent to those skilled in the art that various modifications and variations may be made in the embodiments without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment may be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
While the following description is directed to the exemplary powder treatment systems shown in the figures, it should be understood that the structures and methods described herein may be used in connection with any powder treatment system, especially systems designed for applying materials (e.g., a coating, a nanotube, etc.) to particles, such as, for example a chemical vapor deposition (CVD) system, a physical vapor deposition (PVD) system, a plasma deposition system, an electrochemical deposition system, a molecular layer deposition system, or an atomic layer deposition system. Other types of powder treatment systems with which the present structures and methods may be used or adapted for use will be readily apparent to one skilled in the art reading this disclosure.
Directional terms such as top, bottom, and the like are used simply for convenience of description and are not intended to limit the disclosure attached hereto. Also, as used herein, the term “on” includes being in an open or activated position, whereas the term “off” includes being in a closed or inactivated position. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components.
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Process tube 200 is a vacuum chamber in which the treatment processes (e.g., CVD, sputtering, electron beam evaporation, thermal evaporation, etc.) take place. Load lock chamber 500 is essentially an auxiliary, secondary vacuum chamber attached to process tube 200 with vacuum valve 300 between the chambers. Load lock chamber 500 has its own high vacuum pumping system and venting (not explicitly shown). It contains two (or more) stations each configured for receiving a barrel containing powder to be treated. A mechanical transfer mechanism is provided to move barrels to and from process tube 200. Load lock chamber 500 reduces the cycle time of processing powder and reduces the potential for contamination in process tube 200. Barrels 100 are loaded into the load lock chamber 500 while at atmospheric pressure and temperature, and may contain air. Barrel 100 within load lock chamber 500 may then be preheated, load lock chamber 500 pumped down to a high vacuum pressure, and filled with an inert gas. Vacuum valve 300 is then opened between load lock chamber 500 and the process tube 200. Barrel 100 is then mechanically transferred from load lock chamber 500 to process tube 200 by means of a linear transfer mechanism. After the powder is processed, barrel 100 is transferred back to load lock chamber 500. During this process, the process tube 200 is always under vacuum and maintained at or near treatment temperature. Thus, load lock chamber 500 allows powder to be transferred into the process tube 200 without venting process tube 200 to atmosphere.
Treatment of powder within barrel 100 occurs within process tube 200. In embodiments, treatment of powder can be achieved as described in the '851 application. As described therein, the system may vary the speed of rotation of barrel 100 (which is essentially a rotary treatment vessel) containing the powder to be treated depending upon the presence or absence of net gas flow through the barrel 100 or process tube 200 at different stages of the treatment process. During treatment stages where gas flow may be present (e.g. pump down), barrel 100 is spun at a centrifugal speed. During treatment stages where net gas flow may be minimal or introduced into barrel 100 in such a way as to avoid or substantially minimize disturbance of the particles, the rotational speed of barrel 100 is at a cataracting speed, which is less than a centrifugal speed. Cataracting (with or without a comb) is the condition under which the uniform processing (heat treatment, surface modification, thin film deposition, etc.) should take place for best results. This is also the condition that is most susceptible to elutriation since the fine powder particles are distributed evenly and falling throughout barrel 100 by design and therefore are easily entrained in any net gas or vapor flow through the reactor. Entrained particles may be elutriated out with the exhaust resulting in yield loss or equipment issues including contamination of valves, clogging of filters, etc. By ensuring that, during treatment stages, any net gas flow may be minimal or introduced into barrel 100 in such a way as to avoid or substantially minimize disturbance of the particles, elutriation losses or equipment issues are avoided or substantially reduced.
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In aspects, the present disclosure relates to methods of powder treatment.
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When processing of the powder is complete, end cap 275 moves back through and to the far side of load lock chamber 500 (left in the Figures), elevators 610 and load arms 550a, 550b shuffle around, removing processed barrel 100a away from the center line of process tube 200 and loading the next barrel 100b onto receiving fixtures 560. Loading and processing sequences are then repeated.
While this second barrel 100b is in process, the first barrel 100a is cooling. The load lock chamber 500 (which has been under vacuum since after the hinged barrel doors closed) can be brought back to atmospheric pressure, hinged door (not shown) opened, first barrel 100a removed, and a third barrel (not shown) introduced into load lock chamber 500 in the location from which barrel 100a was removed.
Any variety of treatment processes may be employed to treat powder within the barrel once it is loaded into the process chamber. These various processes may involve treatment sequences during which treatment temperature, pressure, and the flow of process gas (or gases) can be varied over time. Many such process variations are within the purview of those skilled in the art.
At step 940, the vacuum valve is closed, and the rotation of the barrel is slowed down to create a cataracting condition within the barrel. Once a cataracting condition is achieved, process gas is turned on and the process tube and barrel are backfilled to a target pressure for treatment (945). At step 950, with the flow of process gas turned off, treatment continues until the depletion of precursor is achieved. Once the precursor is depleted, at step 955, the rotation speed of the barrel is increased to achieve a centrifuging condition. The vacuum valve is opened, and the process tube and barrel are pumped down at step 960. It should be understood that steps 940 through 960 may be repeated as many times as necessary to complete the powder processing.
At step 965, the vacuum valve is closed, and the process tube and barrel are backfilled with inert gas. The flow of gas is turned off, the vacuum valve is opened, and the process tube and barrel are pumped down at step 970. It should be understood that steps 965 and 970 may be repeated as many times as necessary to pump-purge the process tube and barrel.
At step 975, the vacuum valve is closed, and inert gas is backfilled to offload pressure within the process tube and barrel. The rate of rotation of the barrel is then reduced from a centrifuging speed to zero at step 980. The barrel is unloaded from the process chamber and moved to the load lock chamber at step 990, at which time the hinged door to the load lock chamber can be opened. Care should be taken to minimize pressure differential between the load lock chamber and process chamber when the hinged door opens. Alternatively, the barrel may continue to rotate at a centrifuging speed during unload from the process chamber to the load lock chamber.
This written description uses examples to describe the present powder treatment system and processes to enable any person skilled in the art to make and use any devices or systems and perform any incorporated methods. The scope of the disclosure may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of this disclosure if they include structural elements that do not differ from the explicitly disclosed embodiments, or if they include equivalent structural elements with insubstantial differences from the explicitly disclosed embodiments.
It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with a particle treatment system.
This application claims the benefit of, and priority to, U.S. Provisional Patent Application No. 63/407,766 filed on Sep. 19, 2022, the entire contents of which are hereby incorporated herein by reference.
Number | Date | Country | |
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63407766 | Sep 2022 | US |