Patent Publication Number: US-2021172052-A1

Title: Vapor deposition apparatus and method

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 15/202984 filed Jul. 6, 2016. 
    
    
     BACKGROUND 
     Certain ceramic processing occurs under vacuum, such as physical vapor deposition (PVD) or directed vapor deposition (DVD). Source material is typically fed into a crucible, which is held at vacuum inside a processing chamber. This source material can be a ceramic ingot. 
     SUMMARY 
     A vapor deposition apparatus according to an example of the present disclosure includes a chamber configured to operate at vacuum and at least one crucible in the chamber. The crucible is configured to receive an ingot, a feeder operable to move the ingot with respect to the at least one crucible, and a heater in the chamber and configured to heat a hot zone between the at least one crucible and the feeder. 
     In a further embodiment of any of the foregoing embodiments, the feeder includes a drive mechanism and a mechanical guide mechanism or guide rods. 
     In a further embodiment of any of the foregoing embodiments, the heater is between the mechanical guide mechanism or guide rods and the crucible. 
     In a further embodiment of any of the foregoing embodiments, the heater is fixed to the crucible. 
     In a further embodiment of any of the foregoing embodiments, the heater is an induction heater. 
     In a further embodiment of any of the foregoing embodiments, the heater is a microwave heater. 
     In a further embodiment of any of the foregoing embodiments, the heater is a resistance heater. 
     In a further embodiment of any of the foregoing embodiments, the heater is selected from a group consisting of an induction heater, a microwave heater, and a resistance heater. 
     In a further embodiment of any of the foregoing embodiments, the heater circumscribes the hot zone. 
     In a further embodiment of any of the foregoing embodiments, the heater is operable to heat the hot zone above the vaporization temperature of water across a typical range of thermal emission physical vapor deposition (TE-PVD) process pressures. 
     A further embodiment of any of the foregoing embodiments includes heat shields defining the hot zone. 
     A method for vapor deposition according to an example of the present disclosure includes driving off moisture from an ingot in a vapor deposition chamber prior to the ingot entering a crucible, and providing the ingot to the crucible for vapor deposition. 
     A further embodiment of any of the foregoing embodiments includes feeding the ingot through a hot zone and into the crucible. 
     In a further embodiment of any of the foregoing embodiments, the hot zone is defined between an ingot feeder and the crucible. 
     In a further embodiment of any of the foregoing embodiments, the moisture is driven off as the ingot is fed through the hot zone. 
     In a further embodiment of any of the foregoing embodiments, heat is retained by providing heat shields. 
     A further embodiment of any of the foregoing embodiments includes heating the hot zone with a heater that is in the chamber. 
     In a further embodiment of any of the foregoing embodiments, the heater is selected from a group consisting of an induction heater, a microwave heater, and a resistance heater. 
     In a further embodiment of any of the foregoing embodiments, the ingot is heated to a temperature above the vaporization temperature of water. 
     In a further embodiment of any of the foregoing embodiments, the heater circumscribes the ingot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
         FIG. 1A  illustrates a process chamber. 
         FIG. 1B  illustrates a side view of a process chamber. 
         FIG. 2  illustrates an induction heater for the process chamber of  FIG. 1 . 
         FIG. 3  illustrates an example microwave heater for the process chamber of  FIG. 1 . 
         FIG. 4  illustrates a resistance heater for the process chamber of  FIG. 1 . 
         FIG. 5  illustrates a vapor deposition method. 
     
    
    
     DETAILED DESCRIPTION 
     Thermal emission physical vapor deposition processes (TE-PVD), such as electron beam physical vapor deposition (EB-PVD) and electron beam directed vapor deposition (EB-DVD), are used to deposit coatings. Such processes can be used to deposit ceramic coatings, for example. In vapor deposition processes, an energy source such an electron gun heats, melts, and vaporizes a source ingot, such as a ceramic material. The vapor condenses and deposits on an article in a vapor field, usually above the ingot. In an EB-DVD process, a gas stream (either inert or reactive) can be used to enhance transport of the vapor towards the article. Such processes are typically performed under vacuum and at high heat. 
       FIGS. 1A-1B  illustrate a vapor deposition apparatus  10 . The vapor deposition apparatus  10  includes a process chamber  12  that is configured to operate at vacuum and at high temperatures. For example, the process chamber  12  can be connected in a known manner to gas sources and a vacuum pump system, etc., not described herein. The process chamber  12  includes at least once crucible  14 , a feeder  16 , and a heater  18  between the crucible  14  and the feeder  16 . In this example, the process chamber  12  includes a single crucible  14 . However, it should be understood that the process chamber  12  may include multiple crucibles  14 . The process chamber  12  also includes at least one energy source  17 . In this example, the energy source  17  is an electron gun. Inside the process chamber  12  is an article  20  to which a coating is to be applied by a vapor deposition process. In one example, the article  20  is a component for a gas turbine engine, such as an airfoil. 
     The feeder  16  has a drive mechanism  22  that provides the ingot material  28 , such as ceramic, to the crucible  14  via an aperture  24 . The feeder  16  also has a mechanical guide mechanism or guide-rods  26  to guide the ingot  28  into the aperture  24 . The ingot  28  can be provided in the form of a cylinder, but is not limited to such a geometry. The feeder  16  advances the ingot  28  into the crucible  14  at a predetermined rate. In one example, the rate is 2 mm per minute (0.08 inches per minute). The energy source  17  melts and vaporizes the top of the ingot  28  as it is delivered into the crucible  14 . 
     Situated between the crucible  14  and the feeder  16  is a hot zone  30 . The heater  18  is operable to heat the hot zone  30  across a typical range of TE-PVD process pressures. In this example, the heater  18  is fixed to the crucible  14  by fasteners  32  and is arranged on top of the guide mechanical guide mechanism or rods  26 . In some process chambers  12 , the crucible  14  may move throughout the vapor deposition process. In this example, the heater  18  would move with the crucible  14 . 
     The ingot  28  passes adjacent the heater  18  as it advances through the hot zone  30  and the aperture  24  into the crucible  14 . If the process chamber  12  includes multiple crucibles  14 , each crucible  14  has a heater  18  fixed to it. Because the heater  18  is adjacent the crucible  14  and is inside the process chamber  12 , there is no need for the ingot  28  to be separately heated outside the process chamber  12 , and then inserted into the process chamber  12 , minimizing the risk of burns or other injury to the operator. 
     In one example, the heater  18  heats the ingot  28  such that substantially all of the water in the ingot  28  is evaporated off. In one example, the heater  18  heats the ingot  28  to a temperature of above about 350° F. (177° C.). In a further example, the heater  18  heats the ingot  28  to a temperature between about 350° F. (177° C.) and 400° F. (204° C.). 
     The heater  18  transfers heat to a ‘moist’ ingot  28 , which causes any water in the ingot  28  to evaporate. Ingot  28  drying can occur at ambient pressure, or at vacuum while a vacuum is being applied to the process chamber  12 . Shields  34 , such as lightweight metal or composite shields, can be used to surround the hot zone and concentrate heat on the ingot  28 . 
     In one example, shown in  FIG. 2 , the heater  18  is an induction heater  180 . The induction heater  180  includes a coil  182 , such as a water-cooled high-frequency coil, that circumscribes the ingot  28 . The coil  182  can have a frequency that corresponds to the density and shape of the ingot  28 . The induction heater  180  also includes a power source  184 . An induction heater  180  allows for very concentrated and quick heating of the ingot  28 . 
     In another example, shown in  FIG. 3 , the heater  18  is a microwave heater  280 . The microwave heater  280  includes a microwave output antenna  282 , water line connections  284  for providing cooling water to the heater  280 , a power input  286 , and a power source  288 . Microwave energy from the antenna  282  is absorbed by water in the ingot  28  as it passes by the microwave heater  280 . This process is called dielectric heating. 
     In a third example, shown in  FIG. 4 , the heater  18  is a resistance heater  380  connected to a power source  382 . 
     Because the ingot  28  is substantially freed of water as it travels through the hot zone  30  before entering the crucible  14 , the risks of cracking or fracture, delayed drying, process contamination, ‘spitting’ of molten ceramic, or the like, are reduced. 
       FIG. 5  shows a method for vapor deposition  500 . In step  502 , an ingot  28  is heated. In step  504 , vacuum is applied to a crucible  14 . In step  506 , the ingot  28  is provided to the crucible  14  after the crucible  14  reaches vacuum. 
     Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims.