Sharon L. Nunes

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.

Oxygen induced adhesion degradation at metal/polyimide interface

The role of oxygen in affecting the adhesive bonding at the metal/polyimide (polyimide‐on‐metal) interface has been studied. Both pyromellitic dianhydride (PMDA) ‐oxydianiline (ODA) and biphenyl‐tetracarboxylic dianhydride(BPDA) ‐p‐phenylene diamine (PDA) based poly(amic acid) precursors were cast and fully imidized on metal surfaces of Cr, Cu, Ni, Co, Cu/Ni, and Cu/Co in a nitrogen atmosphere. The peel strengths at the polyimide‐on‐metal interface were measured, using a 90° peel test, immediately after curing, and then remeasured after annealing in either nitrogen (N2−≤100 ppm O2 ) or air (N2 –21% O2 ) at 350 °C for 1 h. Very little or no change in peel strength was measured after these samples were annealed in nitrogen, while significant adhesion degradations were measured on all metals after annealing in air. The loss of polyimide (PI) adhesion to the Cu or Co surface is attributed to metal catalyzed thermal–oxidative degradation of the PI at the metal/PI interface, as characterized by polyimide thickn...

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. >

ADHESION PROPERTIES OF A STRUCTURAL ETCH STOP MATERIAL FOR USE IN MULTILAYER ELECTRONIC WIRING STRUCTURES

A thermally stable copolymer of a polyimide and a dianiline terminated polydimethylsiloxane has been developed for use as a structural oxygen etch barrier material in high performance multilayer electronic wiring structures. We report on the preparation of the etch barrier material and on investigations of the etch stop and adhesion properties of this material. Studies on the effects of adhesion-promoting plasma treatments are supported by x-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS) data. Before plasma treatment, it is observed that the siloxane component segregates to the surface. After either an O 2 reactive ion etch treatment or H 2 O plasma exposure, the unusual XPS charging effects are interpreted as a surface layer containing two distinct phases: the etched polyimide fraction and a partial overlayer of a carbon containing SiO 2

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>>

RBS analysis of Si diffusion in photoresist during silylation

Abstract The diffusion of Si in thin films of photoresist during silylation was investigated using Rutherford backscattering spectroscopy (RBS) and the chemical reaction was studied by X-ray photoemission spectroscopy (XPS). Initially, Si diffuses very rapidly, then it slows down as the silylation time increases. Almost all the Si needed to form a stable cross-linked matrix is achieved within 5 min of silylation. With reactive ion etching (RIE) the etch rate of the silylated photoresist depends on the silylation time and whether the sample is blown dry, air-dried or rinsed immediately after the silylation process. A long silylation time results in the formation of a thin layer of SiO2 on the resist, which increases the RIE resistance.

Extending the innovation ecosystem

What Is Innovation? It¿s not always about inventing something entirely new. Innovation occurs at the intersection of invention and insight. It¿s about the application of invention ¿ the fusion of new developments and new approaches to solve problems. (Sam Palmisano, Delivered at the Council on Competitiveness Annual Meeting, Washington, D.C., October 30, 2003).