Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of coating supply or source outside of primary...
Reexamination Certificate
1995-06-07
2001-08-07
Padgett, Marianne (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of coating supply or source outside of primary...
C427S596000, C118S719000, C118S730000, C118S733000, C118S725000
Reexamination Certificate
active
06270861
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to methods and apparatuses for preparing thin films and, more specifically, to a method and apparatus which separates the deposition or material addition environment from the film crystallization or growth environment, thereby allowing each to be optimized individually. The film resides mostly in the second environment, being very briefly but repeatedly exposed to the first for new material deposition. Pulsed laser ablation is used to provide the very short intense pulses of material which makes such a process feasible.
BACKGROUND OF THE INVENTION
Preparation of thin crystalline films of compound materials has proven difficult where one or more of the component elements are too volatile at the crystal growth temperature to maintain stoichiometry in the film. Examples of materials where this problem exists include high temperature oxide superconductors such as Y1Ba2Cu3ox, Tl2Ba2Ca2Cu3Ox, and variants, other multi-element metal oxides, and compound semiconductors such as GaAs, GaAlAs, GaInAs, and HgCdTe.
Many of the deposition processes, which give excellent crystalline films of single elements or compounds of elements with similar volatilities have difficulty with compound materials whose elements differ widely in volatility. Most of these processes work best at vacuum or near-vacuum pressure. These processes include low pressure chemical vapor deposition (LPCVD), sputtering, E-beam evaporation, molecular beam epitaxy, pulsed laser ablation, and pulsed electron beam ablation.
Several of these conventional processes require an anneal step to be performed at much higher pressure of the volatile element in order to restore the stoichiometry. This procedure is less and less effective as the film thickness is increased.
Other problems inherent in this field include film surface temperature determination and control, problems of handling and risk of contamination of substrates and films due to thermal pastes, and vacuum system contamination and personnel exposure to toxic chemicals. Moreover, a continuing need exists for improved sample throughput and automation, and for the elimination of ablation target overheating and ablation particle contamination of deposited films.
The use of excimer lasers in the deposition of YBCO thin films is described in “Physics of In-Situ Laser Deposition of Superconducting Thin Films” by H. S. Kwok et al.,
SPIE
Vol. 1187, p. 161 (1989). This article notes the significance of target interaction conditions and the properties of the laser-generated plume to the formation of high quality films.
Another excimer laser deposition technique is described in “In-Situ Growth of Superconducting YBa
2
Cu
3
O
y
Films By Pulsed Laser Deposition” by J. B. Boyce et al.,
SPIE
Vol. 1187, p. 136 (1989). Here, the authors noted that diminished transport properties correlate with the imperfect alignment and epitaxy of the YBCO and substrate. Experiments were conducted using a ten-sided polygon target holder and a laser pulse frequency of 1 to 10 Hz.
Further laser ablation techniques are described in “Superconducting Bi—Sr—Ca—Cu—O Films Prepared by Laser Ablation” by A. Gupta et al.,
SPIE
Vol. 1187, p. 130 (1989), and “Preparation and Characterization of Pulsed Laser Deposited HTSC Films” by L. Schultz et al.,
SPIE
Vol. 1187, p. 204 (1989).
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus and method for preparing thin films in which the deposition or material addition environment is separated from the film crystallization or growth environment, whereby the parameters for said material addition and growth can be optimized individually.
Another object of the present invention is to provide an apparatus and method for preparing thin films capable of achieving film surface temperature determination and control.
Another object of the present invention is to provide an apparatus and method for preparing thin crystalline films of compound materials where one or more of the component elements are too volatile at the crystal growth temperature to maintain stoichiometry in the film, while allowing proper pressure for the deposition process.
A further object of the present invention is to provide an apparatus and method which provides film temperature control while preparing thin crystalline films, thereby eliminating the need for thermal paste in substrate mounting, and reducing the need for handling and risk of contamination of substrates and films.
These and other objects are achieved by providing an apparatus for forming thin films which includes first means for containing a target material, second means, in communication with the first means, for containing a substrate, and third means for maintaining a pressure differential between the first and second means.
Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred but non-limiting embodiments of the invention.
REFERENCES:
patent: 3227132 (1966-01-01), Clough et al.
patent: 4430149 (1984-02-01), Berkman
patent: 4508049 (1985-04-01), Behn et al.
patent: 4866032 (1989-09-01), Fujimori et al.
patent: 4949669 (1990-08-01), Ishii et al.
patent: 4966887 (1990-10-01), Garvey
patent: 5015492 (1991-05-01), Venkatesan et al.
patent: 5085166 (1992-02-01), Oka et al.
patent: 5145713 (1992-09-01), Venkatesan et al.
patent: 5207884 (1993-05-01), Char et al.
patent: 5242706 (1993-09-01), Cotell et al.
patent: 5254832 (1993-10-01), Gartner et al.
patent: 5258366 (1993-11-01), Nagaishi et al.
patent: 5308461 (1994-05-01), Ahonen
patent: 5316585 (1994-05-01), Okamoto et al.
Miura et al, “Structure & Superconducting Properties of YBaCuO Films Prepared by Transversely Excited Atmospheric Pressure CO2Pulsed Laser Evaporation,”Appl. Phys. Lett.52(12) Mar. 1988, p1008-10.*
Sankur et al. “Formation of Dielectric & Semiconductor Thin Films by Laser-Assisted Evaporation,” 1988—(No month available), p. 271-284 Journal Source Unknown.*
Marquardt et al, “Deposition of Laser Produced Carbon Films from Laser Produced Plasmas,”Mat. Res. Symp. Proc., vol. 30, 1985 (No month) p. 325-330.*
Preparation and Characterization of Pulsed Laser Deposited HTSC Films by L. Schultz et al., SPIE vol. 1187 Processing of Films for High TcSuperconducting Electronics (1989) No month.
Superconducting Bi-Sr-Ca-Cu-O Films Prepared By Laser Ablation by A. Gupta et al., SPIE vol. 1187 Processing of Films for High TcSuperconducting Electronics (1989) No month.
Layered Growth of HTSC Thin Films Using Pulsed Laser Deposition by Tomoji Kawai et al., SPIE vol. 1187 Processing of Films for High TcSuperconducting Electronics (1989) No month.
Substrates for HTS Films by Randy W. Simon, TWR Space & Technology Group, SPIE vol. 1187 Processing of Films for High TcSuperducting Electonics (1989) No month.
In-situ growth of superconducting YBa2Cu3Oyfilms by pulsed laser deposition by J.B. Boyce et al., SPIE vol. 1187 Processing of Films for High TcSuperconducting Electronics (1989) No month.
Physics on In-Situ Laser Deposition of Superconducting Thin Films by H. S. Kwok et al., SPIE vol. 1187 Processing Films for High TcSuperconducting Electronics (1989) No month.
Craig George L.
Marasco Joseph A.
Padgett Marianne
U-T Battelle, LLC
LandOfFree
Individually controlled environments for pulsed addition and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Individually controlled environments for pulsed addition and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Individually controlled environments for pulsed addition and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2488149