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Fan-out wafer-level package for memory applications

By Ho-Young Son, Ki-Jun Sung, Jong-Hoon Kim, Kangwook Lee [SK hynix Inc.]

R ecently, through-silicon chip stackable fan-out wafer-level Introduction

via (TSV) technologies
TSV technology is very effective
one of the thinnest packages that
have been widely used in package – will be int roduced as as a way to increase the memor y
high-bandwidth memory (HBM) for ha s bet ter t her mal, mecha n ical, capacity by accommodating multiple
high-performance computing (HPC) or and electrical perfor mances than chips in a package—it has also been
graphics applications and high-density c onve nt ion a l w i r e - b on d e d t y p e a leading advanced technology in
memory modules for DDR4/DDR5. memory packages. This package has me mor y ap pl icat ion s. Howeve r,
For mobile memory packaging, wire a z-height that is 15~20% thinner TSV technology and its stacked chip
bonding technology is still being used than conventional wire bonding- packages require a lot of additional
because of the high manufacturing based ball grid array (BGA) packages; back-end processes and, therefore,
cost of TSVs and the performance this was achieved by eliminating i nc r e a se d m a nu fa c t u r i ng c o st s.
compatibility of conventional wire organic substrates. For thermal and Therefore, applications using TSVs are
bonding technologies. As the overall mechanical characterization, the limited to leading-edge products like
m o b i l e s y s t e m p e r f o r m a n c e i s thermal resistance and warpage of HBM for HPC or graphics applications
improved, however, the conventional a package were evaluated. Channel and three-dimensional stacking (3DS)
mobile package may have several characteristics of memory chips were for high-density memory modules (see
challenges with respect to the need for evaluated and it was found that the Figure 1) [1,2].
a thinner package or for better thermal package had enhanced timing margin Contrary to the applications noted
and electrical performance. and power distribution network (PDN) above, mobile applications are still
In this article, the Hynix Integrated impedance compared with the wire- cost sensitive and are consistently
Fa n - ou t M e m o r y ( H I F O M ) – a bonded type packages. faced with requirements for thinner

Figure 1: Memory applications using TSVs: a) 2.5D system in package (SiP) with HBM; b) schematic of a HBM known-good stacked die (KGSD); c) a 3DS memory
module; and d) a schematic of a 3DS package.

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