Innovative Sub-5- $\mu$ m Microvias by Picosecond UV Laser for Post-Moore Packaging Interconnects
IEEE Transactions on Components, Packaging and Manufacturing Technology(2019)
摘要
This article presents for the first time microvias scaled down to sub-
$5~\mu \text{m}$
in diameter fabricated using picosecond UV laser ablation in a nonphotoimageable dielectric film. The motivation of this article is to address post-Moore and More-than-Moore packaging interconnect needs. Microvias play a critical role in package interconnections in IO density and the IC bump pitch for 2.5-D interposers and fan-out packages. UV laser ablation has been the key technology for fabricating small microvias in high density interconnect (HDI) packaging for more than two decades. The state-of-the-art microvia fabricated by UV laser ablation is still at
$20~\mu \text{m}$
in diameter and 50
$\mu \text{m}$
in pitch. This article explores the feasibility of fabricating microvias of
$5~\mu \text{m}$
or less in diameter with a commercially available picosecond UV laser system. The experimental results show that microvias of
$5~\mu \text{m}$
or less in diameter in a 5-
$\mu \text{m}$
-thick Ajinomoto buildup dielectric film (ABF) are achieved. This article also addresses the fundamentals of picosecond pulsed laser ablation on polymer dielectric materials and processes optimization to generate sub-5-
$\mu \text{m}$
microvias. The via pitch of 8–
$12~\mu \text{m}$
is demonstrated. UV laser ablation also addresses the issue of limited availability of photosensitive dielectric materials for photolithography-based microvia fabrication.
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关键词
Laser ablation,Copper,Packaging,Fabrication,Lithography,Substrates,Surface emitting lasers
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