Russell J. Serino

High-speed signal propagation on lossy transmission lines

This paper addresses some of the problems encountered in propagating high-speed signals on lossy transmission lines encountered in high-performance computers. A technique is described for including frequency-dependent losses, such as skin effect and dielectric dispersion, in transmission line analyses. The disjoint group of available tools is brought together, and their relevance to the propagation of high-speed pulses in digital circuit applications is explained. Guidelines are given for different interconnection technologies to indicate where the onset of severe dispersion takes place. Experimental structures have been built and tested, and this paper reports on their electrical performance and demonstrates the agreement between measured data and waveforms derived from analysis. The paper addresses the problems found on lossy lines, such as reflections, rise-time slowdown, increased delay, attenuation, and crosstalk, and suggests methods for controlling these effects in order to maintain distortion-free propagation of high-speed signals.

Fabrication and performance studies of multilayer polymer/metal interconnect structures for packaging applications

Multilayer copper/polyimide interconnect structures were fabricated using a reactive-ion-etching-based lift-off technique. Conductor cross-sectional area control, planarity, and a gap-free structure were made possible by the use of a novel siloxane-polyimide. The resultant structure consisted of two signal wiring layers between two ground planes with a nominal impedance of 40 Omega . Although redundant metallization processes were found to repair open lines, they resulted in an increase of the number of processing steps and could result in an increase of defects. Stud chain structures were found to survive cooling to 77 K with very little change in their characteristics, while heating of the copper interconnections to 350 degrees C in a reducing environment reduced their resistance by 3%.<<ETX>>

Factors affecting the interconnection resistance and yield in multilayer polyimide/copper structures

The use of a lift-off technique to fabricate a high-density structure consisting of multiple layers of metal/polyimide thin-film structures on a silicon substrate is described. To achieve better performance and high yield, the process design, the processing parameters, the thickness of the Cr/Cu/Cr metallurgy, and the use of suitable polyimide dielectrics, were evaluated. The plasma processing conditions, the types of passivation metals on Cu, and the use of a siloxane-polyimide as the gap-fill/etch-stop material were all shown to play a critical role in affecting the interconnection resistance and yield of the multilayer thin-film structures. By optimizing these parameters the feasibility of fabricating high-density thin-film wiring layers with good yield is demonstrated. >

Factors affecting the interconnection resistance and yield in the fabrication of multilayer polyimide/metal thin film structures

The use of a lift-off technique to fabricate a high-density structure consisting of multiple layers of metal/polyimide thin film structure on a silicon substrate is described. To achieve better performance and high yield, the authors evaluated the process design, the processing parameters, and the thickness of the Cr/Cu/Cr metallurgy, along with the use of suitable polyimide dielectrics. The plasma processing conditions, the types of passivation metals on Cu, and the use of a siloxane-polyimide as the gap-fill etch-stop material were all shown to play a very critical role in affecting the interconnection resistance and yield of the multilayer thin film structures. By optimizing these parameters the feasibility of fabricating high-density thin film wiring layers with good yield is demonstrated.<<ETX>>