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Hi-resolution dry-film PID material for high-density packaging

By Yuya Suzuki, Chihiro Funakoshi, Daisuke Shibata, Daichi Okamoto, Yoko Shibasaki [Taiyo Ink Mfg. Co.., Ltd.]
T his paper reports a new dry- technology. Also, the PID

film type photo-imageable
dielectric (PID) material for has high tensile strength
and elongation, which
fine-pitch and high-density multi-layer are beneficial for high
RDL structuring. High-density packaging resistance to mechanical
technologies are substantially required for stresses— especially
high-speed signal transmission in a variety when it is applied for a
of applications, such as high-performance multi-layer RDL.
computing, artificial intelligence (AI), T h i s p a p e r f i r s t
and 5G communications. To achieve high describes the benefits
functionality, new integrated circuit (IC) and challenges of our Table 1: Material properties of a new PID.
packaging technologies including fan- previous generation PID
out wafer-level packaging (FOWLP), material (original PID), and then reports PID material processing
fan-out panel-level packaging (FOPLP), the technical development and evaluation PID materials are organic dielectrics
and high-density substrates have been of the latest PID material (new PID) with with fine-patterning capability by
intensively studied and developed. These respect to solvent resistance and dielectric photolithography processes (Figure
technologies endeavor to have high- resistance. To demonstrate the reliability 1). First, the PID is laminated on base
density redistribution layers (RDLs) of the new PID, test coupons for line- substrate layers by vacuum lamination.
for signal routing with <5µm fine-pitch to-line reliability and layer-to-layer After the lamination, photopatterning
L/S Cu wiring and <10µm small interlayer reliability were fabricated, and biased w it h u lt r av iolet ( U V ) ex p os u r e
via structures. Evolution in semi-additive highly-accelerated stress tests (BHAST) tools are perfor med, followed by
process (SAP) technology has enabled 2µm were conducted. polyethylene terephthalate (PET) film
L/S wiring formation by applying the latest removal and development processes.
materials and processing technologies.
However, current mainstream laser
processing for via formation by CO 2 laser
or Nd-YAG laser cannot achieve ultra-
small vias <10µm [1,2].
Although new laser processing such
as short-wavelength solid lasers and
excimer lasers have been developed
to achieve <10µm via structures [3,4],
installation of new laser tools requires
a large investment, careful handling,
and laborious maintenance. On the
other hand, photosensitive dielectric
materials can form small vias by existing
photolithography stepper or mask
aligner tools, so the materials are useful
for high-density RDL manufacturing.
Taiyo Ink has developed a new PID
material, featuring: 1) Dry-film type for
high surface planarity; 2) Low curing
temperature (180°C); 3) Low coefficient
of thermal expansion (CTE); 4) High
resolution for 6-10µm via formation;
5) Resistance to organic solvents; and
6) High dielectric reliability. Table 1
summarizes the material properties of the
PID. The material has low CTE, which is
enabled by organic-inorganic composite
Figure 1: Process flow of PID patterning.

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