Microwave Characterization of Low-k Dielectric Thin Films using Microstrip Transmission Lines

Abstract

In order to reduce the effects o f the parasitic RC time delay the microelectronics industry is moving to low-k dielectric materials for use with metal lines in future integrated circuit chips, as outlined by the International Technology Roadmap for Semiconductors. The high frequency electrical properties o f these new low-k materials are not always well known. This thesis presents a method to study the electrical properties o f several candidate low-k materials at frequencies o f 0.5 to 13.5 GHz using microstrip transmission lines both before and after chemical mechanical planarization (CMP). The microstrips are fabricated on wafer samples consisting of a 300 nm low-k thin film, and 100 nm SiC interlayer, using DC magnetron sputtering, laser beam photolithography, and reactive ion etching. In order to etch through the SiC under layer for a proper ground contact with the substrate, a reactive ion plasma etch process using RF magnetron sputtering with tetrafluoroethane and oxygen gases was also developed. A SiC etch rate with respect to oxygen concentration investigation was also entailed m this thesis. The electrical properties were measured with an Agilent 8719ES network analyzer and a Cascade Microtech microwave probe station.