Innovative Sub-5-μm Microvias by Picosecond UV Laser for Post-Moore Packaging Interconnects

Fuhan Liu, Gaurav Khurana, Rui Zhang, Atom Watanabe, Bartlet H. Deprospo, Chandrasekharan Nair, Rao R. Tummala, Madhavan Swaminathan

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


This article presents for the first time microvias scaled down to sub- 5μm 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 20μm in diameter and 50 μm in pitch. This article explores the feasibility of fabricating microvias of 5μm or less in diameter with a commercially available picosecond UV laser system. The experimental results show that microvias of 5μm or less in diameter in a 5- μm-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-μm microvias. The via pitch of 8-12μm is demonstrated. UV laser ablation also addresses the issue of limited availability of photosensitive dielectric materials for photolithography-based microvia fabrication.

Original languageEnglish (US)
Article number8839861
Pages (from-to)2016-2023
Number of pages8
JournalIEEE Transactions on Components, Packaging and Manufacturing Technology
Issue number10
StatePublished - Oct 2019

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering


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