2.2.1 | Liquid Metal Mediated (LMM) Epitaxy

The earliest known predecessor of SMME is liquid metal mediated (LMM) epitaxy[1][2] in which epitaxial growth of c-Si at a buried interface using liquid gold (Au) as a mediator for the deposited Si was reported. Due to a lack of substrate cleaning methods and impure Si sources, the growth of Si whiskers was observed.

With improved vacuum equipment and substrate cleaning methods, Ge diffused through a liquid Au mediator grew homoepitaxially at the buried Ge/Au interface after 20 minutes of annealing Figure 2.1.[3]

Fig02_01a.png

(a)

Fig02_01b.png

(b)

Figure 2-1. Liquid Metal Mediated (LMM) Epitaxy. a) A molecular beam of diffusors is deposited atop a liquid layer of metal mediator. b) The product of LMM is a substrate/LMM film/liquid mediator sandwich. The resulting structure requires an annealing stage to improve the quality of the buried LMM layer.

 

SMME requires no additional stages of annealing, and the mediator can be reused for subsequent deposition stages, or incorporated as part of the final device structure.

 

References

  1. R. S. Wagner and Ellis, W. C., “Vapor-Liquid Solid Mechanism of Single Crystal Growth”, Appl. Phys. Lett, vol. 4, 1964.
  2. R. S. Wagner and Ellis, W. C., “Trans. Metall. Soc, A. I. M. E.”, Trans. Metall. Soc., vol. 233, 1965.
  3. F. Xiong, Ganz, E., Loese, A. G., Golovchenko, J. A., and Spaepen, F., “Liquid Metal Mediated Homoepitaxial Film Growth of Ge at Low Temperature”, Appl. Phys. Lett, vol. 59, 1991.