ISTFA 2015 – Outstanding Paper:

Corrosion Mechanisms of Cu Bond Wires on AlSi Pads
Wentao Qin (Technology Assessment and Characterization Lab, ON Semiconductor, Phoenix, AZ, USA)

Abstract
Cu wires were bonded to AlSi (1%) pads, subsequently encapsulated and subjected to uHAST (un-biased Highly Accelerated Stress Test, 130ºC and 85% relative humidity). After the test, a pair of bonding interfaces associated with a failing contact resistance and a passing contact resistance were analyzed and compared, with transmission electron microscopy (TEM), electron diffraction, and energy-dispersive spectroscopy (EDS). The data suggested the corrosion rates were higher for the more Cu-rich Cu-Al intermetallics (IMC) in the failing sample. The corrosion was investigated with factors including electromotive force (EMF), self-passivation of Al, thickness and homogeneity of the Al-oxide on the IMC, ratio of the Cu-to-Al surface areas exposed to the electrolyte for an IMC taken into account. The preferential corrosion observed for the Cu-rich IMC is attributed to the high ratios of the surface areas of the cathode and anode that were exposed to the electrolyte, and the passivation oxide of Al with the lower homogeneity. The corrosion of the Cu-Al IMC is just a manifestation of the well-known phenomenon of dealloying. With the understanding of the corrosion mechanisms, prohibiting the formation of Cu-rich IMCs is expected be an approach to improve the corrosion resistance of the wire bonding.

IPFA 2016 - Best Paper for Reliability:

To be announced July 21, 2016

IRPS 2016 - Best Paper:

Quantitative Model for Post-program Instabilities in Filamentary RRAM
R. Degraeve, A. Fantini, G. Gorine*, P. Roussel, S. Clima, M. Chen, B. Govoreanu, L. Goux, D. Linten, M. Jurczak, A. Thean, imec, *University of Pavia

Abstract
Filamentary vacancy-based RRAM devices show post-program instability, making Incremental Step Pulse Program (ISPP) algorithms highly ineffective.
This is because after the verify step, both the Low and High Resistive State distributions always evolve towards a wider natural distribution. In this paper, we describe this instability in the context of the hourglass model. Both HRS and LRS distributions have two variability sources: (i) number variations of the amount of vacancies in the filament constriction and (ii) constriction shape variations. The shape variations show a log(time)-dependent relaxation behavior after each programming pulse, resulting in program instability. This is mathematically described as an auto-correlated step process of the shape parameters in the QPC conduction model.