An Electrochemical Study of Undercutting during Etching of Duplex Metal Films

For various technological applications patterns are chemically etched in metal films partly covered with a nobler metal. As a result of the bimetallic contact, accelerated etching may occur, giving rise to considerable undercutting. From electrochemical considerations it was expected that the use of certain chemical polishing solutions would significantly reduce the degree of such undercutting. This was verified by studying the electrochemical properties of various polishing and nonpolishing etching agents. Suitable solutions were developed for the etching of Al, Mo, and Ni‐P. These etching agents, when used to etch metal films partly covered by nobler metals, gave markedly less undercutting than nonpolishing etching agents.