Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Patent
1990-10-01
1992-05-05
Beck, Shrive
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
427 39, 118723, B05D 306
Patent
active
051106191
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
Ionically conductive film is used in electrochemical cells such as solid electrolyte fuel cells (hereinafter referred to as SOFC), sensors, displays and so on. Whether it is an insulating film for surface treatment or for use in the fabrication of a semiconductor substrate or an electronically conductive film for use as an electrode material, super-conductive material or the like, there are cases in which the film acquires ionic conductivity during formation.
The present invention relates to a method for producing a film which is ionically conductive at least in the course of film formation.
BACKGROUND ART
As conventional film production technology, there is known an electrochemical vapor deposition method which Isenberg et al. developed for the manufacture of stabilized zirconia film for SOFC (cf. Japanese Patent Kokai Publication 61-153280). In the production of an yttria-stabilized zirconia film on a porous support by this electrochemical vapor deposition method, one side of the porous substrate is exposed to water vapor (H.sub.2 O) including oxygen (O.sub.2) or hydrogen (H.sub.2) and the other side to a gaseous mixture of zirconium tetrachloride (ZrCl.sub.4) and yttrium trichloride (YCl.sub.3).
In this film production method, the oxygen source gas molecules diffuse through pores of the support and react with the metal halide gas on the other side of the support to produce a thin film of yttria-stabilized zirconia on the surface of the support (CVD process). As this film grows, the pores of the support are blocked and the oxygen source gas molecules then cannot pass through the support any longer. However, because the yttria-stabilized zirconia film thus formed is ionically conductive, the oxygen source gas molecules are able to drift through the film in the form of oxygen ions (O.sup.2-). Here, the O.sup.2- concentration gradient caused in the film by the difference in oxygen partial pressure between two sides of the film provides a driving force for ion transport. Therefore, the O.sup.2- ions diffuse through the film to meet with the metal halide gas to sustain the growth of the film (EVD process).
The electrochemical vapor deposition method, consisting of the above-mentioned two stages, viz. CVD and EVD, has the disadvantage that since the ion transport in the latter EVD process is dependent on the intramembrane concentration gradient of O.sup.2- ion, the film formation in the EVD process is slow. This is because negative charges left over by O.sup.2- ions accumulate on the growth side of the film and the potential barrier produced by these surface charges seriously interferes with the transport of other O.sup.2- ions. In order to improve the driving force of reaction, it might be contemplated to increase the difference in oxygen partial pressure between the two sides of the growing film but if the oxygen partial pressure on the metal halide gas side is reduced too much, the resulting film will have a surface composition deviating from the expected composition.
The present invention has been accomplished with the above-mentioned circumstances in view. Thus, the object of the invention is to provide a method of producing a film which provides a desired surface composition while improving the rate of film formation in the EVD stage of the conventional electrochemical vapor deposition method.
DISCLOSURE OF INVENTION
The film forming method according to the present invention is characterized in that the growth of a film is promoted by removing the electric charges accumulating on the growth side of the film in the course of film formation. More particularly, the invention is characterized by applying an external electric field in the thickness direction of the film in the course of film formation to accelerate the ion transport and establishing a plasma in front of the film growing surface.
Removal of charges on the growth side of the film precludes formation of a potential barrier on this surface. Therefore, the ion transport in the film in the course of formation is not inhibited
REFERENCES:
patent: 4298629 (1981-11-01), Nozaki et al.
patent: 4901669 (1990-02-01), Yamamoto et al.
Ogumi Zempachi
Takehara Zenichiro
Beck Shrive
King Roy V.
LandOfFree
Method for production of films does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for production of films, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for production of films will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1411284