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bridge is only around 6mm x 6mm! There
are two important assembly processes
involved in making an EMIB. First, in the
panel format, single or multiple bridges
are embedded into a semi-finished high-
density build-up organic substrate with
a very high-precision die attach tool.
It is then followed by a high-density
and fine line and space electrochemical
metal deposition (ECD) process for the
RDL formation. Moving forward it is
foreseeable that when the geometry of chip
I/O bump pitch features shrink further, the
requirement on bridge placement accuracy
will become more stringent.
A l t ho u g h E M I B i s i d e a l f o r
integ rating multiple components
without the scaling limitations found
®
with CoWoS , there is also concern in
deploying this technology. The chip
layout needs to align with the package
Figure 2: Packaging technologies in different HI levels.
architecture. This means that the I/Os
types of inter posers is to reduce of those connected chips need to couple
the manufact uring cost. Because well with the multiple interconnecting
the components to be integrated are bridges. As a result, there are concerns
increasing in quantity, the resulting with respect to how far the embedded
interposer size is also getting larger. bridge solution can be utilized in the
The challenge of using such large open market.
interposer integrated die is severe Heterogeneous integrated fan-out
warpage that occurs when it is being (HIFO) approach. The HIFO approach
flip-chip attached onto the substrate. is based on high-density wafer-level
Figure 3: Typical structure of an interposer. Thermal compression bonding has

wafer yield with smaller die size had been a proven way to ove rcome
shown significant improvement, while the the integrated die war page issue.
FPGA performance was unaffected with The industry’s interposer roadmap
®
the CoWoS structure. indicates that they are expected to
One of the important design aspects increase in size to 100mm x 100mm,
of the CoWoS TSV inter poser is however not many large interposers
®
to maintain the die-to-die electrical can fit onto a 12” Si interposer wafer. Figure 5: Typical structure of heterogeneous
communication performance. Both Therefore, the scalability of the TSV integrated fan-out (HIFO) technology.
signal and power integrity are very interposer is limited.
important design aspects. Another Emb e d de d br i d ge a ppr o ach. fan-out (HD WLFO) technology with
i mp or t a nt a dva nt age of u si ng a The embedded bridge approach is both die-first and RDL-first processes,
TSV interposer is the matching of considered a good approach to mitigate together with the structure to integrate
its coefficient of thermal expansion the TSV interposer scalability limitation multiple components with RDL fine
(CTE) with the chiplet because they (Figure 4). In 2014, Intel introduced its line and space geometr y (Figure
are both silicon. For over a decade, embedded multi-die interconnect bridge 5). This approach has been widely
besides usage in FPGAs, both high- (EMIB) invention through a processor deployed by outsourced semiconductor
end graphics processing units (GPUs) module named Lakefield, in which an assembly and test suppliers (OSATS)
and network processors made use of EMIB bridge connects a Radeon Vega like ASE, which has developed fan-out
®
CoWoS structures to be integrated CPU with HBM. The size of the EMIB chip-on-substrate FOCoS technology.
with high-bandwidth memory (HBM) A core WLFO package size is typically
components. There are other types around 5mm x 5mm, however a HIFO
of i nter poser mater ials, such as package size can achieve much larger
glass and organic interposers, that body sizes. ASE – using its FOCoS
are being developed. The former is structure – has demonstrated package
enabled by through-glass via (TGV) sizes of more than 25mm x 25mm. The
technology, and the latter make use HIFO integrated die is not directly
of thin-film technology. One of the Figure 4: Typical structure of the embedded mounted on a board, but is mounted on
com mon objectives of these new bridge approach.

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