Coating apparatus – Control means responsive to a randomly occurring sensed... – Responsive to condition of coating material
Reexamination Certificate
1998-02-06
2001-12-11
Mayes, Curtis (Department: 1734)
Coating apparatus
Control means responsive to a randomly occurring sensed...
Responsive to condition of coating material
C118S690000, C118S900000, C438S795000, C438S798000, C055S340000, C055SDIG003, C096S109000, C261SDIG002, C422S234000
Reexamination Certificate
active
06328801
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a novel method for recovering and recirculating a deuterium-containing gas. The invention also relates to a system for recovering and recirculating a deuterium-containing gas. The invention finds particular applicability in an annealing process during semiconductor device manufacturing.
2. Description of the Related Art
Basic processing steps involved in the manufacture of integrated circuits (ICs), for example, metal oxide semiconductor (MOS) ICs, include epitaxial growth, wafer cleaning, photolithography, ion implantation, diffusion, chemical vapor deposition (CVD), sputtering, etching and electrical testing.
Following metallization and prior to electrical testing of the devices, annealing of the wafers containing the devices under a “forming gas” atmosphere is known. A typical forming gas atmosphere includes from 5 to 10 percent by volume hydrogen (H
2
) diluted in nitrogen (N
2
).
The purpose of this annealing step is to passivate defects, or surface states, at the MOS interface generated during earlier IC manufacturing steps. Such surface states include, for example, dangling silicon bonds at the silicon surface and interface trap charge Q
it
present at the Si/SiO
2
interface. Such defects can degrade the operating characteristics of the formed device by effectively removing charge carriers needed for the operation of the device or, alternatively, by the generation of unwanted charge carriers.
Notwithstanding the use of such an annealing process, high energy charge carriers may induce a “depassivation” of the previously passivated defects during normal operation of, for example, a MOS transistor. This depassivation can lead to subsequent, progressive degradation of the electrical properties of the transistor. The aging characteristics of the IC, in turn, become detrimentally affected. See, e.g., R.A.B. Devine et al, Applied Physics Letters, 70(22), p. 2999 (1997).
The above-described phenomena have become more and more problematic with the increases in electric field intensity brought on by increased device integration and the shrinking geometries associated therewith. Device lifetime may thus become unacceptably short for future generations of integrated circuits.
To address these problems, it has recently been proposed to conduct the post-metallization annealing step using pure deuterium (D
2
) or a deuterium-containing gas mixture in place of pure hydrogen (H
2
) or a hydrogen-containing gas mixture. In so doing, it has been shown that submicron MOS transistor lifetime can be significantly increased over that attained using hydrogen. The use of a deuterium-containing annealing atmosphere is discussed, for example, in International Publication No. WO 94/19829, which discloses contacting a silicon wafer with a deuterium-containing material to form Si—D and Si—OD bonds on a silicon surface at an interface with a silicon dioxide layer.
While the use of deuterium in the post-metallization annealing process is of great interest, its application on an industrial scale has, to date, been impractical. This impracticality is a result of the high cost and limited availability of the deuterium isotope. In particular, for the deuterium flowrates required, the cost of treating chamber exhaust as waste gas can be prohibitive.
SUMMARY OF THE INVENTION
The aforementioned problems associated with the state of this art have been overcome or conspicuously ameliorated by the processes and systems in accordance with the invention.
According to a first aspect of the present invention, a novel method of recirculating a deuterium-containing gas is provided. The method comprises the steps of: (a) introducing a deuterium-containing feed gas into a chamber; (b) removing from the chamber an exhaust gas containing deuterium; (c) adjusting the deuterium concentration of the exhaust gas to a predetermined value, thereby producing a concentration-adjusted gas stream; and (d) introducing the concentration-adjusted gas stream into the chamber as the deuterium-containing feed gas.
A second aspect of the invention involves a system for carrying out the process described above. The system comprises: (a) a gas introducing line for introducing a deuterium-containing feed gas into a chamber; (b) an exhaust line for removing from the chamber an exhaust gas; (c) a makeup gas line for adding a makeup gas containing deuterium to the exhaust gas; and (d) means for adjusting the deuterium concentration of the exhaust gas to a predetermined value to produce a concentration-adjusted gas as the deuterium-containing feed gas.
Through the invention, a method and system for recovering and recycling a deuterium-containing gas stream have been realized, which find particular applicability in the manufacture of semiconductor devices. In a particularly advantageous aspect of the invention, the post-metallization annealing of semiconductors in a deuterium atmosphere can be practiced on an industrial scale. The inventive method and system make the use of deuterium commercially feasible, and result in marked improvements in device lifetime as compared to hydrogen treatment.
REFERENCES:
patent: 3849204 (1974-11-01), Fowler
patent: 3923559 (1975-12-01), Sinha
patent: 4113514 (1978-09-01), Pankove et al.
patent: 4151007 (1979-04-01), Levinstein et al.
patent: 4331486 (1982-05-01), Chenevas-Paule et al.
patent: 4460673 (1984-07-01), Sukigara et al.
patent: 4476094 (1984-10-01), Carson
patent: 4521698 (1985-06-01), Taylor
patent: 4620211 (1986-10-01), Baliga et al.
patent: 4691433 (1987-09-01), Pimbley et al.
patent: 4859620 (1989-08-01), Wei et al.
patent: 4915912 (1990-04-01), Walles et al.
patent: 5059551 (1991-10-01), Chevallier et al.
patent: 5177571 (1993-01-01), Satoh et al.
patent: 5229311 (1993-07-01), Lai et al.
patent: 5352914 (1994-10-01), Farb
patent: 5872387 (1999-02-01), Lyding et al.
patent: 02-218128 (1990-08-01), None
patent: WO94/19829 (1994-09-01), None
Biersack et al, “Radiation Effects and Defects in Solids,”Gordon and Breach Science Publishers, (1989), pp. 301-308.
Mikkelsen, Jr. et al, “Secondary Ion Mass Spectrometry Characterization of D2O and H218O Steam Oxidation of Silicon,”Journal of Electronic Materials, vol. 11, No. 3, 1982, pp. 541-558.
Myers et al, “Interactions of deuterium with ion-irradiated SiO2on Si,”J. Appl. Phys., 67 (9), May 1, 1990, pp. 4064-4071.
Oehrlein et al, “Secondary Ion Mass Spectrometry Measurements of Deuterium Penetration into Silicon by Low Pressure RF glow Discharges,”Gordon and Breach Science Publishers, Inc., vol. 111 & vol. 112 (1-2) pp. 299-300.
Park et al, “The Effect of Annealing Treatment on the Distribution of Deuterium in Silicon and in Silicon/Silicon Oxide Systems,”J. Electrochem. Soc., vol. 139, No. 7, Jul. 1992, pp. 2042-2046.
Saks et al, “Time-dependence of the interface trap build-up in deuterium-annealed oxides after irradition,”Appl. Phys. Lett., 61 (25), Dec. 21, 1992, pp. 3014-3016.
Friedt Jean-Marie
Gary Daniel
Girard Jean-Marc
Rostaing Jean-Christophe
Burns Doane Swecker & Mathis L.L.P.
L'Air Liquide, Societe Anonyme pour l'Etude et l'
Lorengo J. A.
Mayes Curtis
LandOfFree
Method and system for recovering and recirculating a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for recovering and recirculating a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for recovering and recirculating a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2594923