Open AccessAssembly of Cu Wirings with Ultrasmooth and High-Adhesive Electroless Cu Seed Layer by Using UV Modification and Low Attenuation of High-Frequency Transmission Property
Author(s) -
Masaya Toba,
Shuji Nomoto,
Nobuhito Komuro,
Kazuyuki Mitsukura,
Shinichiro Abe,
Takashi Masuko,
Kazuhiko Kurafuchi
Publication year - 2020
Publication title -
journal of microelectronics and electronic packaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.192
H-Index - 17
eISSN - 1555-8037
pISSN - 1551-4897
DOI - 10.4071/imaps.1100914
Subject(s) - materials science , dielectric , optoelectronics , photoresist , adhesive , surface modification , layer (electronics) , copper plating , composite material , chemical mechanical planarization , printed circuit board , nanotechnology , chemical engineering , electrical engineering , electroplating , engineering
Semiconductor packages for high-performance devices with printed circuit boards having multiwiring layers such as flip-chip ball grid array have been attracting the attention to realize ultrare-liable and low-latency communications in 5G networking. Cu wirings for the package are usually fabricated by via formation by laser for dielectric, desmear, electroless Cu seed formation, photoresist patterning, electrolytic Cu plating, resist stripping, and seed layer etching. Although a desmear process can obtain enough adhesion between dielectric and Cu seed layer by anchoring effect to secure reliabilities, the interface between dielectric and Cu seed layer should be smooth to achieve low attenuation of electric signals at high frequencies. Here, instead of a desmear process, we applied a UV modification for the surface of dielectric to realize a smooth and high-adhesive seed layer against dielectric. We obtained .8 kN/m of peel strength between dielectric and Cu seed layer in spite of surface roughness of the dielectric being 45 nm by a nanolevel anchoring effect at the UV-modified layer. Because of the smooth interface by UV modification, the S21 value of microstrip line was 26% improved compared with that assembled through the desmear process at 60 GHz.