Cleaning of Gold Interconnection Surface by Low-temperature Hydrogen Annealing for MEMS Device Fabrication

摘要

A technique for cleaning a gold surface using a dry process is described for the fabrication of microelectromechanical system (MEMS) devices. X-ray photoelectron spectroscopy (XPS) shows that gold is oxidized after exposure to oxygen plasma used for ashing of organic contaminants or etching of a sacrificial-layer film. On such oxidized gold surface, there are different incubations at the different places, which give rise to non-uniform thickness in film growth by electrochemical techniques, such as electrodeposition and electroplating. A surface analysis by thermal desorption spectroscopy (TDS) revealed that annealing causes oxygen to desorb from the gold oxide. The surfaces were annealed in a vacuum or nitrogen or hydrogen ambient to examine the effectiveness of dry-process surface cleaning. For the annealing in a vacuum and nitrogen ambient, a temperature of over 260℃ is necessary for the oxide removal. Annealing in hydrogen ambient drastically lowers the cleaning temperature from 260 to 110℃.