Coating processes – Direct application of electrical – magnetic – wave – or... – Electromagnetic or particulate radiation utilized
Reexamination Certificate
2000-09-26
2004-05-04
Padgett, Marianne (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Electromagnetic or particulate radiation utilized
C427S552000, C427S540000, C427S581000, C427S580000, C216S094000, C216S063000, C204S164000, C219S121120, C219S121240
Reexamination Certificate
active
06730370
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to processing of materials, including growth or deposition of the materials, and also to removal of materials. More specifically, the invention relates to a method and apparatus for locally raising the temperature of a material in order to facilitate chemical reactions or changes in physical state related to processing of the material by using an electrode tip, such as an electron emitter tip, to apply a controlled succession of thermal annealing spikes (hereinafter referred to as thermal spikes) or shockwaves of varying energy through a growth or removal medium (hereinafter referred to as a growth medium, even though the medium could also be used in processes involving etching or cleaning and no “growth”). The scale of the thermal spikes or shockwaves, and the area of the material affected by the resulting energy transfer, is on the order of a few nanometers to several hundred micrometers, and the duration of the thermal spikes or shockwaves ranges from a few picoseconds to several hundred nanoseconds. The growth medium may be a cryogenic liquid, although it is within the scope of the invention to use other growth media, including liquids, solids, gases in critical or non-critical state, and mixtures of liquids and solids, solids and gases, and liquids and gases.
The method and apparatus of the invention may be used for a variety of industrial applications and manufacturing processes, including deposition and/or growth of thick or thin film crystalline or non-crystalline materials, etching or cleaning of materials, and formation of nanostructures.
2. Description of Related Art
A. Introduction
The problem addressed by the present invention is the problem, common in the field of materials processing, of how to add energy during processing of a material in order to speed-up chemical reactions or processes, overcome energy barriers, or otherwise improve processing efficiency or product quality, without generating defects or damaging in the material, and/or without interfering with other reactions or processes necessary to provide an acceptable end product.
The oldest and simplest way to apply energy to a material during processing is simply to process the material in a high temperature environment as in, by way of example, physical vapor deposition (PVD), chemical vapor deposition (CVD), or metalorganic chemical vapor deposition (MOCVD). Alternatively, energy may be applied directly to a material being deposited or transferred, as in sputter deposition and various etching methods, by using shockwaves as in explosive bonding methods, or by direct application of energy using lasers or radiation. In all such materials processing methods, the objective has always been to transfer the necessary energy in the most efficient manner while minimizing any damage that might occur as a result of the energy transfer.
The present invention also addresses the problem of energy transfer efficiency and damage mitigation, but utilizes a mechanism different from all other known materials processing methods and apparatus, namely the application, in the presence of a growth medium, of a controlled succession of thermal spikes or shockwaves of varying energy to a nanoscale area of the material.
The term “nanoscale” as used herein refers to dimensions on the order of less than one nanometer (including atomic dimensions of approximately 0.1 to 0.15 nm) to several tens of micrometers, as opposed to the dimensions of the non-localized high energy shockwaves produced by spark discharges for the purpose of vaporizing materials in order to facilitate binding of coatings to a surface, as described for example in U.S. Pat. No. 3,663,788. The use of shock waves on a macroscopic scale is a variation of the explosive bonding technique used to join otherwise incompatible metals, which is fundamentally different than the much more controlled application of energy provided by the present invention.
The most relevant prior art known to the inventor, which shares with the present invention localization of the energy transfer, and the use of a cryogenic growth medium (optional in the present invention), is the “cryogenic furnace” technique disclosed in U.S. Pat. No. 3,720,598. According to this technique, an oscillating Josephson junction having “extremely small dimensions” is formed by spark erosion between capacitor electrodes made up of the materials to be vaporized, thereby concentrating as much energy as possible on a small area.
The present invention shares with the cryogenic furnace concept the temporal and spatial localization of energy applied to a material for the purpose of “establishing chemical and physical state in materials” (col. 1, lines 14-27 of U.S. Pat. No. 3,720,598), and in particular to facilitate growth or removal of materials, as well as the use (in a preferred embodiment of the present invention) of a cryogenic medium through which the energy is applied, but is distinguishable in a number of ways:
instead of using a plasma arc discharge to temporarily vaporize the medium and material being processed, the present invention uses electron emission (either from an electron emitter tip, or from the workpiece or growth medium in case the polarity of the emitter tip is reversed) to generate thermal spikes or shockwaves that propagate in the medium in order to enable a more controllable energy transfer, eliminating the high energy plasma ions inherent in plasma discharge arrangements;
The impulses are controlled to provide a succession of spikes of varying energy rather than a steady state or oscillating field;
The size of the area affected by the discharge is reduced even further than in the cryogenic furnace technique to nanometer or atomic scale, thereby reducing the overall amount of energy that needs to be supplied to achieve a desired local temperature; and
The apparatus in which the growth or removal of materials takes place is adapted to facilitate insertion and removal of materials from the growth medium, cleaning of the growth medium, as well as insertion and removal of the substrate on which growth occurs or from which material is to be removed, so as to enable use of the system in industrial manufacturing processes.
These differences are critical to the practicality of the present invention relative to the technique disclosed in U.S. Pat. No. 3,720,598. While capable of delivering high energy levels to a small area, the cryogenic furnace technique described in U.S. Pat. No. 3,720,598 ultimately proved impractical for manufacturing purposes because of the inability to prevent destruction of an unacceptably high percentage of the grown material by the high energy tail in the distribution of ions created by the plasma arc. Furthermore, alternative techniques that were eventually implemented in the years following the originally cryogenic furnace proposal, such as electron synchrotron radiation, laser heating, and rapid thermal annealing, while more controllable and less destructive, are capable of delivering only a relatively small amount of energy over a relatively large area, barely sufficient to break chemical bonds and improve mobility on growing surfaces. To date, the most promising of these methods is electron synchrotron radiation, but this method requires equipment costing a minimum of $100 Million, and is not readily available or adaptable to ordinary manufacturing.
While the present invention shares with several of the above-mentioned prior arrangements the concept of applying spatially and temporally localized bursts of energy to a material in order to change its physical or chemical state and facilitate material growth, the manner of energy delivery is fundamentally different, involving the propagation in the growth medium, and in particular a cryogenic growth medium, of nanoscale bursts of energy in an arrangement adapted for mass processing of the materials to be grown or otherwise altered or formed.
The method and apparatus of the invention may be used as a replacement for a variety of conve
Bacon & Thomas PLLC
Padgett Marianne
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