Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – Insulated gate formation
Reexamination Certificate
1999-09-16
2001-04-10
Chaudhuri, Olik (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
Insulated gate formation
C427S595000, C427S596000, C117S105000, C117S938000, C148S033000, C438S785000
Reexamination Certificate
active
06214712
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the construction of thin films onto semiconductor surfaces and relates, more particularly, to the construction of a thin-film build-up onto semiconductor surfaces utilizing physical vapor deposition techniques.
Heretofore, much of the success of silicon metal-oxide-semiconductor (MOS) structures in microprocessor and memory technologies has been largely dependent upon the formation of well-defined SiO
2
-on-silicon (abbreviated SiO
2
/Si) structures wherein SiO
2
serves as the gate oxide. However, for silicon MOS devices, including silicon metal-oxide-semiconductor field effect transistor (MOSFET) devices, there is considerable interest in replacing SiO
2
with a deposited dielectric material possessing a higher dielectric constant. Furthermore, semiconductor materials—other than those which include silicon—are likely to become attractive for use in digital switching applications if methods are developed for forming well-defined oxide/semiconductor interfaces suitable for functional MOS-type structures. For example, Ge is an attractive semiconductor material for microelectronic applications because Ge possesses higher carrier mobility and a higher thermal conductivity than that of silicon. However, the native germanium oxides are not suitable for MOS-type device structures because these oxides are not very stable. With this in mind, the formation of stable metal oxides on Ge could prove instrumental in the development of Ge surfaces, as well as other non-silicon-including semiconductor surfaces, for use in integrated circuit applications.
For the development of MOS devices which employ a thin-film oxide disposed directly atop a semiconductor material other than silicon for use in applications, such as can include sensor, photovoltaic and optoelectronic applications, the formation of well-defined metal oxide/semiconductor interfaces is of paramount importance. Within the structure of many of such devices, it is preferable that the metal oxide/semiconductor interface be devoid of any native oxide, since the presence of native oxide at the interface is likely to limit the performance of these structures. Accordingly, it would be desirable to provide a method for constructing a thin-film build-up of metal oxide onto a semiconductor surface, other than a surface which includes silicon, wherein the growth of native oxides at the surface/metal oxide interface is minimized. By definition, a native oxide is that oxide (or oxides) which spontaneously forms on the material surface when the material surface is exposed to oxygen at elevated temperatures.
Accordingly, it is an object of the present invention to provide a new and improved method for growing thin-film metal oxide upon a semiconductor surface, other than a surface which includes silicon, which reduces the likelihood that native oxides will form at the surface/oxide interface and structures formed with the method.
Another object of the present invention is to provide such a method which utilizes physical vapor deposition techniques.
Still another object of the present invention is to provide such a method for growing a thin-film metal oxide upon the underlying semiconductor surface wherein the thin-film growth can be used as a template for additional film growth.
Yet another object of the present invention is to provide such a method which is uncomplicated to perform.
SUMMARY OF THE INVENTION
This invention resides in a method for growing a metal oxide thin film upon the surface of a semiconductor with a physical vapor deposition technique wherein constituent atoms of the metal oxide to be deposited upon the semiconductor surface are moved toward the semiconductor surface in a controlled environment and a structure formed with the method.
The process of the invention includes the steps of developing an ultra-high vacuum environment about a semiconductor surface which has been cleaned to atomic cleanliness and wherein the primary vapor constituent of the high-vacuum environment is water. Then the semiconductor surface is heated to an elevated temperature, and hydrogen gas is introduced into the high-vacuum environment so that the surface temperature and the ratio of hydrogen partial pressure to water partial pressure at the semiconductor surface are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. With the aforedescribed elevated temperature and the ratio of hydrogen partial pressure to water partial pressure having been established, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the semiconductor surface by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide so that there exists substantially no native oxide at the semiconductor surface/thin film interface.
The use of hydrogen background gas reduces or eliminates the formation of native oxides during the deposition of a metal oxide layer on a semiconductor surface and leads to a reduction in required temperatures and a relaxation of the background pressure requirements necessary to eliminate the native oxide and achieve growth (including epitaxial growth) of oxides on a single crystal semiconductor surface. Without the use of a hydrogen background gas, a high-temperature annealing in UHV conditions would be necessary in order to desorb the native oxide and achieve epitaxy. The decomposition of a given oxide by hydrogen is determined by the thermodynamic Gibbs free energy of the oxide.
Further still, the invention can be used to construct a distinct article, namely an epitaxial (001) CeO
2
film on (001) Ge, which has not been realized by any other technique. It also provides a route to forming a structure including epitaxial (001) CeO
2
film on a Si substrate (wherein a layer of Ge is interposed between the Si substrate and the CeO
2
film) which has not been achieved heretofore.
Structures constructed with the method of the invention can be used for numerous electronic and optoelectronic devices, including metal-oxide-semiconductor field-effect transistors, random-access memory devices, and optical waveguide structures.
REFERENCES:
patent: 3672992 (1972-06-01), Schaffer
patent: 4159919 (1979-07-01), McFee et al.
patent: 5225031 (1993-07-01), McKee et al.
patent: 5274249 (1993-12-01), Xi et al.
patent: 5347157 (1994-09-01), Hung et al.
patent: 5387459 (1995-02-01), Hung
patent: 5547922 (1996-08-01), Ma
patent: 5731049 (1998-03-01), Taihades et al.
patent: 5795848 (1998-08-01), Ma
patent: 5817531 (1998-10-01), Nakamura et al.
patent: 5834803 (1998-11-01), Nashimoto
K.M. Horn et al, “Oxygen Roughening of Ge (001) Surfaces”, Surface Science 320, 174-184 (1994).
L. Surnev et al, “Oxygen Adsorption on a Ge(100) Surface”, Surface Science 123, 505-518 (1982).
K.J. Hubbard et al, “Thermodynamic Stability of Binary Oxides in Contact with Silicon”, J.Mater.Res. 11, 2757-2776 (1996).
R.A. McKee et al, “Crystalline Oxides on Silicon: The First Five Monolayers”, Physics Review Letters, vol. 81, 3014-3017 (1998).
S.H. Jang et al, “Properties of CeO2Thin Flims Deposited on Si(100) and Si (111) Substrates by Radio Frequency-Magnetron Sputtering”, J.Vac. Sci. Technology B 16, 1098-1101 (1988).
H. Koinuma et al, “Ceramic Layer Epitaxy by Pulsed Laser Deposition in an Ultrahigh Vacuum System”, Applied Physics Letters, vol. 58, 2027-2029 (1991).
T. Inoue et al, “Growth of (110)-oriented CeO2Layers on (100) Silicon Substrates”, Applied Physics Letters, vol. 59, 3604-3606 (1991).
D.P. Norton et al, “Epitaxial Yba2Cu3O7on Biaxially Textured Nickel (001): An Approach to Superconducting Tapes with High Critical Current Density”, Science, vol. 274, 755-757 (1996).
M. Paranthaman et al, “Growth of Biaxially Textured Buffer Layers on Rolled-Ni Substrates by Electron Beam Evaporation”, Physica C 275, 266-272 (1997).
Chaudhuri Olik
Craig George L.
Marasco Joseph A.
McKee Michael E.
Rao Shrinivas H.
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