Coating processes – Coating by vapor – gas – or smoke
Reexamination Certificate
1997-03-03
2001-06-19
Meeks, Timothy (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
C427S255500, C137S56100R, C095S045000, C096S004000
Reexamination Certificate
active
06248399
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the industrial manufacture of new high-performance alloys, functional materials and ultrahigh-purity materials from the vapor phase, including PVD magnesium (PVD: physical vapor deposition), PVD aluminium, PVD titanium, PVD superalloys and PVD intermetallics, (sheets, bars, profiles, forgings, layers and surface films), “Thermal Barriers”, VD materials (VD: Vapor Deposition) of semiconductor technology, including elementary and/or porous silicon, and of distillation for extraction (recovery) and refining, i.e. for the production of high-purity elements, such as alkali, alkaline earth and rare earth metals, to production of high-purity and ultra-high-purity (elementary or basic) metals (transition metals, such as Zr, Cr etc.) and products of “clean-room technolgy” as such, to the production of pigments, of reinforcing components, (of alloys with dispersed) carbides, nitides, borides, oxides, silicides, fullerenes, magnets, of optical and electronic products, including the products of microelectronics, to the coating of the reinforcing components of composite materials, for the surface treatment of materials as such, and to the recycling of modern lightweight and functional materials and of lubricants as well as aqueous solutions beyond the vapor phase, the products deposited from the vapor phase assuming solid massive forms and/or solid powder forms, semifinished product forms and/or near-final contour forms in the elementary and/or alloy state, in the thermodynamically metastable or stable state, whether as metal or ceramic or as semiconductor, or being packaged in liquid form or racked off as a gaseous constituent.
In industrializing the manufacture of future products from the vapor phase, relatively long distances for the conveyanve and for the intermixing (for example, during alloying) and segregating (for example, during recycling) of the relevant vapors will have to be covered in an energy-efficient way. The length of the necessary vapor conveyance flow distances is determined, on the one hand, by the size (quantity and dimension) of the initial, intermediate and resulting products and, on the other hand, on the nature and number of the methods and operative process steps of alloying, distillation and conveyance of (in) the vapor phase. However, overcoming long vapor conveyance flow distances still always tended to involve the problem of high conveying capacities Q, indeed entirely irrespective of the thermal loading capacity and chemical reactivity of the plant materials with and in relation to the corresponding vapors. See Th. König et al., H. C. Starck GmbH & Co KG, D38642 Goslar, German Patent DE 4214720, 11.11.1993.
In vacuum technology, a distinction must be made, as regards results, between two pumping capacities: (i) the first pumping capacity must be applied in order to generate the vacuum, the underpressure or overpressure and/or the controlled atmospheric composition in a system which is virtually closed off relative to the environment, the environment having a pressure of one atmosphere under normal conditions; (ii) the second pumping capacity to be basically distinguished is used for producing controlled (suction) flow and (suction) conveyance movements in the vacuum, in the overpressure prevailing relative to the environment and/or in corresponding atmospheres composed in a controlled manner relative to the environment and/or in corresponding atmospheres composed in a controlled manner relative to the environment, said movements being independent of the absolute pressure value of the respective atmosphere in certain regions (particular to a specific pumping system). Just as a pump can generate an air draft under normal conditions, a pump can generate and drive a vapor flow under vacuum conditions, etc., and the pumping capacity can in various ways be uncoupled from the conveying capacity and, by controlling the conveying capacity, can be coupled to this again. The pump-unspecific pumping speed S at the inlet of a given vacuum pump station for a given vacuum chamber is a mechanical propulsion force which must be delimited relative to chemical and physical conveying operations and which is intended for the forced convection of the conveying, alloying or separating and converting operations involved. It is unimportant, in this case, whether the suction effect is produced by underpressure alone or in conjunction with a carrier gas. The pressure flow is that form of propulsion force of material conveyance which corresponds to the (technical) overpressure, whereas, in a vacuum, the suction flow is this particular form. This distinction, trivial per se, has hitherto greatly underestimated importance in light of the state of vacuvum technology and material production from the vapor phase (see F. Hehmann, F. W. Hugo, F.Müller and M. Raschke, German Patent Application P 44063334, Mar. 1, 1994, made by Leybold Durferrit GmbH, Hanau).
Gaseous suction flows are used (i) in the chemical and petrochemical industry for separating processes for the selection, for example of (for example, organic) solvents in waste air, in which the speed-determining step of diffusion through the diaphragm is controlled according to Fick's law of diffusion. Gaseous suction flows are also used (ii) in chemical vapor deposition processes (CVD), in which a chemical surface reaction and the amount of surface involved determine and limit the productivity of the CVD coating process. In the simplest form, this reaction reads as follows (cf. D. S. Rickerby and A. Matthews,
Advanced Surface Coatings—A Handbook of Surface Engineerings
, Blackie & Son Ltd, Glasgow G64 2NZ, 1991):
2AX(g)+H
2
→A(s)+2HX(g) (1)
in which AX(g) is the gaseous reactant supplied (for example, fluorides, chlorides, bromides, carbonyls, volatile metallo-organic compounds), A is the material of the resulting surface layer (s), H(H
2
) is hydrogen as a carrier and HX is the usually toxic and corrosive waste gas. In this case, the suction flow does not determine the speed-determining process step (and productivity limit), but is used primarily for operating safety. It is therefore also not surprising that, in CVD operations with simultaneously occuring and widely differing surface reaction speeds (the term “reaction kinetics” is avoided here, since it often relates to a reaction mechanism, the speed of which can be influenced by mechanism-independent variables), so-called “additives” are added to the reactants, in order to brake (!) the fastest reaction operation and achieve harmonization of all reaction operations on the corresponding surfaces, that is to say a control of the CVD process. It was thereby possible to achieve an accurate control of the composition and nature of the resulting phases by means of CVD processes. The increase in productivity specific to the CVD process was therefore concentrated on the development of suitable compositions of the react and gases supplied to the reaction (cf. D. C. Boyd, R. T. Haasch, D. R. Mantell, R. K. Schulze, J. F. Evans and W. L. Gladfelter,
Chem. Mater
. 1 (1989), p. 119.) and has consequently hitherto remained independent of the pumping speed S or of the conveying capacity Q which is applied for the waste-gas suction (!) flow.
This is an important reference point in the overall invention designated above: for the purpose of control (of a process), not to accelerate the fastest process step, or even merely to control it, but, above all things, to restrict it! This specific form of process control to increase productivity is the indispensable precondition for the industrialization of an advanced process and allows a better utilization of its inherent advantages. This maxim is pertinent only to those processes which operate in limited areas. Vapor deposition (irrespective of its form (for example, as (reacted) dust, powder, solid blank, etc.) or of its dimension) is such an area, since the fragmentation of matter (which is the decisive criterion for structural
Foley & Lardner
Meeks Timothy
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