Coating processes – Direct application of electrical – magnetic – wave – or... – Photoinitiated chemical vapor deposition
Reexamination Certificate
2000-01-27
2001-02-13
Meeks, Timothy (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Photoinitiated chemical vapor deposition
C427S586000, C427S596000, C427S248100, C427S226000
Reexamination Certificate
active
06187392
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the laser desorption of CVD precursor species and, more particularly, to the desorption of CVD precursor species by heating a target at a rate designed to selectively desorb relatively cool molecules therefrom. Further, the present invention relates to chemical vapor deposition incorporating the laser desorption technique of the present invention.
Stated broadly, chemical vapor deposition (CVD) includes any process in which a material is deposited on a substrate by decomposition of one or more precursor materials within a process chamber. In conventional CVD, the precursor is carried into the process chamber by a carrier gas flow by gradually heating the precursor to a temperature above its vaporization temperature such that the vaporized precursor is entrained in the carrier gas flow. Unfortunately, some CVD precursor materials are difficult to vaporize quickly and uniformly. Other CVD precursors are thermally unstable (i.e., the precursor decomposes) at temperatures required for sublimation. Additionally, the present inventor has identified specific CVD precursor materials characterized by respective decomposition and vaporization temperatures which are very nearly the same. Accordingly, it would not be practical to utilize conventional precursor heating schemes to introduce these precursors into a CVD carrier gas stream because significant decomposition of the precursor would occur upon heating.
Accordingly, there is a need for a system wherein CVD precursor species may be entrained in a carrier gas or otherwise transported to a CVD process without raising the temperature of the CVD precursor to its characteristic vaporization temperature.
BRIEF SUMMARY OF THE INVENTION
This need is met by the present invention wherein CVD precursor particles are desorbed from a target by increasing the temperature of a selected target area at a predetermined heating rate such that heat energy causes the desorption of at least one CVD precursor particle intact from the target, such that intermediate bonds between the precursor particles and adjacent particles are heated at a higher rate than the precursor's internal bonds, or such that a substantial portion of heat energy is not transferred to the internal modes of the CVD precursor particle.
In accordance with one embodiment of the present invention, a chemical vapor deposition process is provided comprising the steps of: positioning a target within a chamber, the target comprising CVD precursor particles; transferring heat energy to a selected target area to induce a predetermined temperature increase in the selected target area, wherein the predetermined temperature increase is characterized by a predetermined heating rate, and wherein the predetermined heating rate is selected such that the heat energy causes the desorption of at least one CVD precursor particle to define a precursor desorption region and such that a substantial portion of the heat energy is not transferred to the internal modes of the CVD precursor particle; and positioning a deposition substrate in particulate communication with the precursor desorption region.
The process may further comprise the steps of: directing the desorbed precursor particle towards a surface of the deposition substrate; and causing the desorbed precursor particle to decompose on the deposition substrate surface. The desorbed precursor particle may be caused to migrate on the deposition substrate surface prior to the decomposition. The desorbed precursor particle may comprise a molecule selected so as to migrate and decompose on the deposition substrate surface upon contact with the deposition substrate surface.
The precursor particles may comprise molecules of a first chemical composition, adjacent particles may comprise molecules of a second chemical composition, and the first chemical composition may be different than the second chemical composition. The precursor particles may comprise precursor molecules and adjacent particles may comprise adjacent molecules bonded to the precursor molecules via van der Waals forces. The precursor particles may comprise precursor atoms and adjacent particles may comprise adjacent atoms bonded to the precursor atoms. Adjacent particles may form a target substrate and precursor particles may be supported by the target substrate. As a final example, adjacent particles and the precursor particles may form a solution.
In accordance with another embodiment of the present invention a chemical vapor deposition apparatus is provided comprising a chamber, a target, a desorption heat source, and a deposition substrate. The chamber defines a precursor desorption region. The target is positioned within the precursor desorption region and comprises CVD precursor particles. The desorption heat source is arranged to induce a predetermined temperature increase in a selected target area by transferring heat energy to the selected target area. The predetermined temperature increase is characterized by a predetermined heating rate and the predetermined heating rate is selected such that the heat energy causes the desorption of at least one CVD precursor particle to define a precursor desorption region and such that a substantial portion of the heat energy is not transferred to the internal modes of the CVD precursor particle. The deposition substrate is positioned in particulate communication with the precursor desorption region. The precursor desorption region and the deposition substrate may be spaced apart along a precursor flow path or may be defined in a common area.
In accordance with yet another embodiment of the present invention a chemical vapor deposition process is provided comprising the steps of: positioning a target within a chamber, the target comprising CVD precursor particles bound to adjacent particles via intermediate bonds; transferring heat energy to a selected target area to induce a predetermined temperature increase in the selected target area, wherein the predetermined temperature increase is characterized by a predetermined heating rate, and wherein the predetermined heating rate is selected such that the intermediate bonds are heated at a higher rate than internal bonds of the precursor particles; and positioning a deposition substrate in particulate communication with the precursor desorption region.
In accordance with yet another embodiment of the present invention, a chemical vapor deposition apparatus is provided comprising a chamber, a target, a desorption heat source, and a deposition substrate. The chamber defines a precursor desorption region. The target is positioned within the precursor desorption region and comprises CVD precursor particles bound to adjacent particles via intermediate bonds. The desorption heat source is arranged to induce a predetermined temperature increase in a selected target area. The predetermined temperature increase is characterized by a predetermined heating rate and the predetermined heating rate is selected such that the intermediate bonds are heated at a higher rate than internal bonds of the precursor particles. The deposition substrate positioned in particulate communication with the precursor desorption region.
In accordance with yet another embodiment of the present invention a chemical vapor deposition process is provided comprising the steps of: positioning a target within a chamber, the target comprising CVD precursor particles; transferring heat energy to a selected target area to induce a predetermined temperature increase in the selected target area, wherein the predetermined temperature increase is characterized by a predetermined heating rate, wherein the predetermined heating rate is selected such that the heat energy causes the desorption of at least one CVD precursor particle intact from the target; and heating a deposition substrate positioned in particulate communication with the precursor desorption region such that the desorbed precursor particle, upon contact with the deposition substrate, migrates and decomposes on the depo
Killworth, Gothman, Hagan & Schaeff, LLP
Meeks Timothy
Micro)n Technology, Inc.
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