Metallic Electrodes; Restrictions and Future Prospective; A Survey on Recent Patents

Metallic electrodes have received great attention for the last thirty years due to their special characteristics and low price. Some properties such as adhesive properties and reliability remained uncertain. There are numerous published reports and patents in the literature which have been dedicated to thin metallic films. However, it has been seen that these reports most likely do not practicable. The goal of this study is to elucidate the restriction toward manufacturer and engineers to employ thin metallic films in microelectronic technology. Main disadvantages of the metallic thin films are classified into three major categories called adhesive properties, interdiffusion and solid state reactions, and hillock formation. Numerous inventions have been proposed to: enhance the adhesive properties of metallic films; suppress the solid state reactions within metallic films which occur at high temperature; and prevent the hillock formation. Applicable inventions are considered and new theories and suppressing procedures are described deeply in this review. This study not only represents the methods and inventions which are able to solve the mentioned problems, but also explains the scientific origin of each method, individually. The other advantage of this work is to introduce the recent progresses on alloy thin films as a potential replacement for metallic thin films.