PICVD is based on a new principle of the formation of organometallic vapour phase. A simple idea became a basis of this principle - the whole amount of precursors mixture must be stored cool, only their microdoses can be introduced into evaporator. This idea allowed to elaborate a simple and precise liquid delivery system for CVD sources based on the principle used for the control of fuel injection in the latest thermal motors.The injected microdose is evaporated instantaneously (flash evaporation), thus there is no time for chemical changes of precursors.

Volatile organometallic precursors or their mixture (e.g., Y, Ba, Cu b-diketonates for YBCO deposition) are dissolved in appropriate organic solvent. The precise microdoses of solution are injected into evaporation zone by means of computer-driven injector, where they instantly evaporate. The resulting mixture of solvent and precursor vapour is transported by carrier gas (Ar, O₂) into high temperature zone where the decomposition reaction and film growth on a substrate occurs. Injector is a high speed micro electro-valve

The advantageous features of PICVD:

• A microdose (1-10 mg) of solution evaporates instantly (flash evaporation) in vacuum (~5 Torr), so
• a mixture of precursors is heated only a short time insufficient for chemical change, so instability of precursors becomes insignificant;
• the composition of vapour phase corresponds to the composition of precursor solution, consequently, it is easy to change and reproduce it.
• A precise microdosing (within ~3 %) of precursors' mixture as well as the possibility to change easily the injection parameters enables the precise control of the vapour pressure, the growth rate and the improvement of the reproducibility of film properties.
• It is possible to deposit films of various composition in-situ in the same PICVD reactor by simple change of solution composition and deposition conditions. Use of several injectors allows production of in-situ  multilayered structures.
• Another pecularity of the process is that it works “digitally”: the thickness may be simply controlled by the number of drops injected, what is very attractive for multilayers. For example, for the deposition of oxide superlattices, the solution concentration, opening time and droplet size can be adjusted to obtain a mean thickness increase at each injection less than 0.1 nm.

 

 

J.P. Sénateur, F. Weiss, O. Thomas, R. Madar, A. Abrutis. Patent No 93/08838 PCT No FR94/00858 (Europe, U.S.A.).

 

J.P. Senateur, A. Abrutis, F. Felten, F. Weiss, O. Thomas, R. Madar. Growth and characterisation of refractory oxide layers by injection-CVD. Advances in Inorganic Films and Coatings. Ed. P.Vincenzini, Techna srl.(Italy), 1995, p. 161-166.

 

F. Felten, J.P. Senateur, F. Weiss, R. Madar, A. Abrutis. Deposition of oxides layers by computer controlled injection-LPCVD. J. Phys. IV France, 5-C5 (1995) 1079-1086.

 

J.P. Senateur, C. Dubourdieu, V. Galindo, F. Weiss, A. Abrutis “Application of Pulsed Injection MOCVD for the Deposition of Oxide Single Layers and Superlattices. In “Innovative processing of films and nanocrystalline povders”, Ed. Kwang-Leong Choy, Imperial College Press, London, UK, 2002, p.71-105. ISBN 1-86094-316-0.

 

A. Abrutis, C. Jimenez. MOCVD "Digital" Growth of High-Tc Superconductors, Related Heterostructures and Superlattices. In: Recent Developments in Superconductivity Research, pp. 133-199 (2006). Editor: Barry P. Martins, Nova Publishers, USA, ISBN: 1-60021-462-2.