公开(公告)号：US3806430A

公开(公告)日：1974-04-23

申请号：US4667770

申请日：1970-06-16

Applicant: IBM

Inventor： LAIBOWITZ R ,  LEVI A ,  ROSENBERG R

IPC: C25D11/02 ,  C23B9/00

CPC classification number: C25D11/02

Abstract: A METHOD IS DISCLOSED FOR PRODUCING DEFECT-FREE ULTRATHIN ANODIC OXIDE FILMS OF LESS THAN APPROXIMATELY 50 A. THICKNESS. ILLUSTRATIVELY, A THIN INSULATING FILM IS FORMED ON A NIOBIUM SUBSTRATE. A RESIDUALL OXIDE HAVING A THICKNESS OF ABOUT 30 A. IS NORMALLY PRESENT ON THE NIOBIUM SUBSTRATE. THE RESIDUAL OXIDE FILM IS REMOVED PRIOR TO ANODIZING, LEAVING MORE UNIFORM NIOBIUM SUBSTRATE. BY ANODIZING UNDER CONTROLLED CONDITIONS ANY DESIRED OXIDE DIMENSION LESS THAN APPROXIMATELY 50 A. MAY BE ACHIEVED BY THE PRACTICE OF THIS DISCLOSURE. THE METHOD COMPRISES ANODIZING THE NIOBIUM SUBSTRATE IN A SUITABLE ELECTROLYTE WITH AN APPLIED POTENTIAL UP TO APPOXIMATELY 1 VOLT, AND SUBSEQUENTLY REMOVING THE RESULTANT OXIDE BY ETCHING WITH A SUITABLE ETCHANT, E.G., HF, AND HF+HNO3, THE ANODIZING-ETCHING STEPS ARE PREFERABLY REPEATED TO REMOVE SURFACE CAVITIES AND GROWTHS FOR OBTAINING A SURFACE ON THE NIOBIUM SUBSTRATE WITH DESIRED UNIFORMITY. ILLUSTRATIVELY, THE FINAL ANODIZATION OF THE NIOBIUM SURFACE IS ACHIEVED BY CONNECTING THE TWO ELECTRODES OF THE ELECTROLYTIC CELL (THE NIOBIUM SURFACE AND THE CATHODE) THROUGH A CONSTANT CURRENT SOURCE TO ACHIEVE THE DESIRED FINAL THICKNESS OF THE ANODIC FILM. ALTERNATIVELY, THE ELECTRODES MAY BE CONNECTED TO EACH OTHER THROUGH A RESISTOR FOR CONTROLLING THE RATE OF ANODIC FILM GROWTH.