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|BEOL Thermal Characterization for 3D Packaging|
|Keywords: BEOL, Thermal, 3D|
|Little research has been conducted to thermally characterize the Back End of Line (BEOL) interconnects, since they play little role in the thermal problem of 2D electronic packages. This is changing with the emergence of 3D packages, which place BEOL layers directly in the thermal path. The BEOL structures cannot be easily accommodated in FEM or CFD package models. With dielectric thermal conductivities in the 0.5-1.5W/mK range, the BEOL layers can be significant components of the total thermal resistance. In this study we describe various BEOL designs and compare the thermal impedance of different structures using detailed finite element micro-models. We compare the results to analytical techniques and simple mixing rules, to find effective resistances and conductivities that can be used in conventional conduction based modeling tools. We have found that the simple series and parallel resistance models might not be adequate to simulate the variety of BEOL interconnect layouts. Joule heating effects will also be addressed. The primary goal of the paper is to establish efficient and accurate ways to account for different BEOL designs in a macro-level model. We will also describe future work to experimentally verify the modeling results using a specially designed test vehicle.|
|Jamil A. Wakil, Engineer