Single-crystal – oriented-crystal – and epitaxy growth processes; – Forming from vapor or gaseous state – With decomposition of a precursor
Reexamination Certificate
2000-11-29
2003-08-12
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Forming from vapor or gaseous state
With decomposition of a precursor
C117S108000, C117S944000, C117S106000, C117S033000
Reexamination Certificate
active
06605151
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to oxide thin films and composites including such materials as can be derived from suitable metal precursors and/or prepared using molecular beam epitaxy techniques. In particular, the present invention relates to use and/or integration of such oxide films in a variety of devices.
BACKGROUND OF THE INVENTION
In recent years there has been increasing interest in thin oxide films as alternative high &kgr; dielectrics. For example, one such material is MgO, which has a dielectric constant of 9.4. Because of its chemical stability and thermodynamic compatibility with silicon (Si), interfacial reactions should be minimal. To date, a variety of deposition techniques have been used to grow MgO thin films on Si including metal-organic chemical vapor deposition (MOCVD), B. S. Kwak, E. P. Boyd, K. Zhang, A. Erbil and B. Wilkins, Appl. Phys. Left., 54 25(1989); E. Fujii, A. Tomozawa, S. Fujii, H. Torii, M. Hattori and R. Takayama, Jpn. J. Appl Phys., 32, L1448(1993); sputtering, S. Fujii, A. Tomozawa, E. Fujii, H. Torii, R. Takayawa and T. Hirao, Appl. Phys. Lett., 65(11), 1463(1994); S. Kim and S. Hishita, Thin Solid Films, 281-282, 449(1996); M. Tonouchi, Y. Sakaguchi and T. Kobayashi, J. Appl. Phys., 62(3), 961(1987); Y. Li, G. C. Xiong, G. J. Lian, J. Li and Z. Gan, Thin Solid Films, 223,11(1993), laser deposition, T. Ishiguro, Y. Hiroshima and T. Inoue, Jpn. J. Appl. Phys., 35, 3537(1996); P. Tiwari, S. Sharan and J. Narayan, J. Appl. Phys., 69(12), 8358(1991); D. K. Fork, F. A. Ponce, J. C. Tramontana and T. H. Geballe, Appl. Phys. Left., 58(20), 2294(1991); S. Amirhaghi, A. Archer, B. Taguiang, R. McMinn, P. Barnes, S. Tarling and I. W. Boyd, Appl. Surf. Sci., 54, 205(1992); e-beam-assisted molecular, beam epitaxy (MBE) F. J. Walker, R. A. McKee, S. J. Pennycook and T. G. Thnndat, Mater. Res. Soc. Symp. Proc., 401, 13(1996); and the sol-gel method J. G. Yoon and K. Kim, Appl. Phys. Lett., 66(20), 2661(1995) However, as would be understood by those skilled in the art, deposition techniques of the prior art are accompanied by various shortcomings and/or deficiencies with respect to the use and applications described herein.
For instance, much current work has focused on the formation of dielectrics by chemical vapor deposition. Because such deposition techniques operate at pressures in excess of 10
−3
Torr, oxidation of a silicon substrate prior to thin film deposition provides an unwanted formation of silicon dioxide. Other work has been performed using electron-beam evaporation of MgO onto Si in an oxygen ambient. The inherent mechanical difficulties associated with using electron-beam sources in an oxygen atmosphere has limited this approach, especially for large area coverage. The technique also requires atomistic control of the amount and type of atomic species deposited to enable epitaxy. This complication has further limited the success of this approach.
A related concern is the integration of functional components on substrates, for instance integration of a ferroelectric thin film on a semi-conductor substrate. It is often difficult to deposit/grow epitaxial thin films of the sort needed for optimal performance on such substrates because of interactive diffusion between the layers, oxidation of the substrate and similar such material or surface incompatibilities. Capping components, typically oxides, can be layered on the substrate to alleviate such difficulties for instance to act as a diffusion barrier. However, introduction of such components can present also promote substrate oxidation and the non-epitaxial growth of a component subsequently integrated thereon.
SUMMARY OF THE INVENTION
Given the problems and deficiencies in the art relating to the preparation and use of oxide thin films, there is a need for an improved approach to such films and composites so as to maximize the benefits available therefrom; e.g., for use thereof with integrated devices.
Accordingly, it is an object of the present invention to provide various deposition methods and techniques overcoming the problems and shortcomings of the prior art, including those described above, such that the resulting films can be used in conjunction with integrated systems and devices. It will be understood by those skilled in the art that one or more aspects of this invention can meet certain objectives, while one or more other aspects can meet certain other objectives. Each objective may not apply equally, in all instances, to every aspect of this invention. As such, the following objects can be viewed in the alternative with respect to any one aspect of this invention.
It can be an object of this invention to provide a thin film fabrication technique which combines the versatility of standard chemical vapor deposition with the molecular beam properties of conventional molecular beam epitaxy.
It can be another object of this invention to provide, in particular, for the use of metal organic molecular beam epitaxy (MOMBE) with suitable metal-organic precursors, such precursors having, without limitation: 1) a very low background pressure (<10
−7
Torr); 2) a single metal-containing volatile species in the molecular beam, 3) a high sticking coefficient, 4) and high long-term stability at the evaporation temperature (no decomposition or oxidation of the source materials), 5) an organic component/ligand accessible commercially or by known synthetic techniques, and 6) sufficient volatility (>10
−6
Torr) at low temperature.
It can also be an object of the:present invention to provide a method for deposition of thin films of nanometer dimensions (less than 50 nm, and preferably less than about 3 to about 10 nm) by molecular beam epitaxy techniques using pressures (oxygen and/or base) lower than those of one prior art and/or to achieve the film composition and/or morphology desired.
It can also be an object of the present invention to provide methods, processes, and/or techniques of the type described herein for the deposition of a variety of alkaline earth and rare earth oxides, from commercially-available metal precursors, without carbon contamination on substrates useful in the fabrication of integrated systems.
It can also be an object of the present invention to provide thin film metal oxides, the metal component thereof including but not limited to Ca, Zn, Cd, V, Rh, Pt, Th, Fe, Pd, Ga, Al, Be, U, Hf, La, Pr, Sm, Gd, Dy, Er, Yb, Sc, Th, Ti, Ba, Ce, Mg and Pb, such films as can be amorphous or provided with glass, crystalline, polycrystalline or epitaxial morphologies.
It can also be an object of the present invention to provide metal oxide films, such as those referenced above, for use in the fabrication of a variety of composites for subsequent integration, such composites including substrates of Si and Ge, or with compound (Group III-V and II-VI) substrates.
It can also be an object of this invention to provide a deposition technique which allows in situ film diagnosis and monitoring, allowing for use of reflection high-energy election diffraction and other diagnostic methods (including MS and RGA) under the vacuum conditions inherent to such a technique.
It can also be an object of the present invention to integrate metal oxide thin films, such as those described above, and/or related composites thereof to provide for one or more devices, such devices having, without limitation, dielectric, refractory, ferro-electric, electro-optical, non-linear optical, field emission, phosphor/luminophor, optical isolation, photonic, waveguide, MOS, MOSFET, semi-conducting, and/or super conducting applications, such devices as can otherwise be fabricated using techniques and components known to those skilled in the art.
In particular, it can also be an object of the invention to provide epitaxial MgO layers on silicon substrates have potential applications in ultra-large scale integration and in microphotonics. Because of the thermodynamic stability of MgO with both silicon and ferroelectric oxide thin films, it can be used as an ideal buffer lay
Hoerman Brent H.
Niu Feng
Wessels Bruce W.
Kunemund Robert
Northwestern University
Reinhart Boerner Van Deuren s.c.
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