Radiant energy – Ion generation – Field ionization type
Reexamination Certificate
2002-03-04
2004-07-20
Lee, John R. (Department: 2881)
Radiant energy
Ion generation
Field ionization type
C204S192120, C315S111810, C315S111010
Reexamination Certificate
active
06765216
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and apparatus for producing flows of molecular gas atoms, in particular an atomic hydrogen flow. The invention is particularly useful in the manufacture, of semiconductor devices and integrated circuits.
RELATED ART
The following is a list of references, which is intended for a better understanding of the background of the present invention.
1. Leone S., Jpn. J. Appl. Phys., 1995, 34. p. 2073-2082;
2. Orlikovsky A. A., Microelectronics, 1999, 28(5), p. 344-362;
3. Roussean A. et al., Pulsed microwave discharge: a very efficient H atom source, J. Phys. D: Appl. Phys., 1994, 27, p.2439-2441;
4. Popov O. A., Waldron H., J. Vac. Sci. Technol. A., 1989, 7(3), p. 914-917;
5. Kroon R., Jpn. J. Appl. Phys., 1997, 36, p. 5068-5071;
6. Bardos L., Barankova H., Berg S., Appl. Phys. Lett., 1997, 70(5), p. 577-579;
7. Lepert G., Thieme H. J., Osten H. J., J. Electrochem. Soc. 1995, V. 142. 1, p. 191-195;
8. Sugaya T., Kawabe M., Jpn. J. Appl. Phys. 1991, 30(3A), p. L402-L404;
9. Wolan J. P., Mount C. K., Hoflund G. B., J. Vac. Sci. Technol., A., 1997, 15(5), p. 2502-2507;
10. D. Korzec et al., J. Vac. Sci. Technol., A, 13(4), 1995, p. 2074-2085;
11. U.S. Pat. No. 5,693,173;
12. Applications Note. EPI MBE Production Group. August/September, 1994;
13. Applications Note. EPI MBE Production Group. Jan. 1, 1996;
14. Livshits A. I., Balghiti F. El., Bacal M., Plasma Source Sci. Technol., 1994, 3, p. 465-472;
15. Hoflund G. B., Weaver J. F., Meas. Sci. Technol. 1994, 5, pp. 201-204;
16. Merfy E., Brofy D., Convenient source with a SHF-discharge in an elongated resonator for producing streams of of hydrogen atoms, Devices for Scientific Investigations, 1979, 5, p. 121-122;
17. Geddes J. et al., Plasma Source Sci. Technol., 1993, 2, p. 93-99;
18. RF Gas Cracker/Reactive Atom Source—HD Series, The product of Oxford Applied Research;
19. U.S., Pat. No. 5,336,533:
20. Goodman R. S., Materer N., Leone S. R., J. Vac. Sci. Technol., B., 1997, 15(4), p. 971-9982;
21. Sherman A., J. Vac. Sci. Thechnol., B, 1990, 8 (4), p.656-657;
22. Samano E. C. et al., Rev. Sci. Instrum., 1993, 64(10), p.2746-2752;
23. Goorrier S. et al., Thin Solid Film, 1981, 84, p. 379-388;
24. RU2088056;
25. Handbook of Ion Sources, Ed. by Bernhard Wolf, CRC Press, 1995, p.544;
26. Gabovich M. D., Pasechnik L. L., Dozovaya E. A., “Output of plasma with high concentration of charged particles into vacuum”, Journal of technical physics, 1961, V. 31, No. 9, pp. 1049-1055;
27. Ito M., Yamamato M., Nakamura S., Hattori T., “Purification of diamond films by applying into the plasma stream in the cathode arc discharge plasma jet chemical vapor deposition technique”, J. Appl. Phys., 1995, 77(12), pp.6636-6640.
BACKGROUND OF THE INVENTION
The manufacture of semiconductor devices and integrated circuits utilize the treatment of semiconductor structures in aqueous chemical solutions (the so-called “wet” methods) and in plasma of various gases (“dry” methods). Lately, there has been significant increase in the use of dry methods as compared to that of wet methods, and treatment in plasma is being replaced by treatment in “remote” plasma.
Dry treatments of semiconductor structures used in the industry utilize known sources of plasma and particles beams based on various configurations of radio-frequency (RF) discharge [2,3], microwave discharge under the condition of electron cyclotron resonance (ECR) [2, 4], glow and arc discharges of direct current [5,6].
A dry treatment technique based on the use of a flow of neutral kinetically enhanced chemically active particles (atoms, radicals and excited particles), and particularly, a flow of atomic hydrogen, has also been developed [1]. This technique is characterized by the minimal level of introduced defects and contaminations, and a high degree of the reproducibility and controllability of a treatment process, and is therefore considered as a perspective technology in the manufacture of semiconductor devices with critical dimensions less than 0.18 &mgr;m. The successive realization of this technique and provision of high rates of treatment of semiconductor wafers requires sources of particles that form flows of hot (E<10 eV) neutral particles of high intensity (10
15
-10
16
cm
−2
s
−1
) at a gas working pressure of less than 10
−2
Pa in a vacuum camera. However, the sources of neutral chemically active particles were less developed, as compared to the sources of plasma and charged particles.
Mostly developed sources of the kind specifies are sources of atomic hydrogen. The production of hydrogen atoms utilizes several effects as follows:
dissociation of molecules of hydrogen while heating a gas, for example, by laser emission [1],
dissociation by means of high-energy photons, for example, in the UV spectral range [7],
dissociation of molecules on a heated metal surface [8],
dissociated adsorption of molecules followed by electron-stimulated desorption of atoms [9], and
dissociation by electron impact [10].
In the atomic hydrogen sources based on the dissociation of hydrogen on a heated metal surface [11, 12], a dissociator is usually implemented either as a spiral-like tungsten wire heated by the electric current passage therethrough, or as a metal tube heated by electron bombardment. Molecules of hydrogen adsorb on the heated metal surface and dissociate into atoms, which can then leave the surface either as atoms, or, after the recombination, as molecules. Desorption results in the formation of a flow of particles composed of a mixture of atoms and molecules of hydrogen. The effectiveness of such sources at a working pressure of about 10
−2
Pa is limited to 3% [12] or 15% [13], and, being defined by a sticking coefficient of molecule, does not exceed 25% [14]. Effectiveness of the sources significantly reduces with the increase of the pressure of hydrogen in the source. This prevents formation of intensive flows of atomic hydrogen. The density of atoms' flow in such a source is typically about 10
14
cm
−2
s
−1
. Additionally, this source suffers from incapability of obtaining hot atoms, because of a low temperature of the heated metal surface (~2000 K).
An atomic hydrogen source based on electron-stimulated desorption of atoms enables formation of atom' flow with the flow density not exceeding 10
14
cm
−2
S
−1
[9, 15] and utilize several sequential physical processes. Initially, the dissociated adsorption of hydrogen molecules takes place on the outer surface of a metal membrane. Then, the atoms diffuse through the membrane, and propagate onto the inner surface of the membrane (in a vacuum). Thereafter, if the atoms are not subjected to any external effect, they will associate into molecules and desorb into vacuum, thereby forming a flow of molecular hydrogen. In order to cause desorption of the atoms from the membrane's surface, the known effect of stimulated desorption under electron bombardment is used. This results in the formation of a flow composed of hydrogen atoms and molecules. Estimations have shown that the atomic hydrogen source of this kind enables obtaining a flow of hot atoms with the energy of 1 eV [9]. However, the effectiveness of such an atomic hydrogen source is limited by a small cross-section of electron-stimulated desorption of atoms. Hence, in order to obtain an atom flow of 10
14
cm
−2
s
−1
, a wide-aperture electron beam with a high current density (more than 10 mAcm
−2
) has to be used. This, in turn, requires using a thermionic emitter of a large surface area heated to a temperature significantly higher than that required in a source utilizing a heated wire. This leads to an increase of the pollution of a semiconductor structure under treatment by tungsten vapor and other products of the desorption process. To provide further growth of the density of an atomic hydrogen flow,
Kagadei Valery A.
Proskurovsky Dmitry I.
Atomic Hydrogen Technologies Ltd.
Fernandez Kalimah
Lee John R.
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