<title>Laser-induced microfracture leading to high-density metal-to-metal connections</title>

Abstract

keywords : laser, repair, interconnect, metal, link AB STRACT Laser programmed inter-level metal connections have been developed as a means to achieve high density linking for customization in programmable gate arrays and for additive redundancy in restructurable integrated circuits. This work reports on the linking of 4 x 4 pm crossings of standard two-level metal interconnect lines and subsequent microstructural analyses aimed at understanding the mechanism of link formation. The links were formed by focusing a laser on metal 1 through an annular region of metal 2. The mechanism of link formation appears to be a physical connection made by a fracture of the inter-level dielectric (ILD) layer due to the stress of thermal expansion of the metallization with molten metal 2 filling the crack. Focussed ion-beam (FIB) cross sectional micrography and finite element analysis (FEA) have allowed us to analyze the successfully formed links as well as the failures to link. As a result of our analysis, we have begun to understand how to optimize the device geometry for very high reliability laser linking.