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and 260°C x 5min reflow. This result thereby became approximately zero. tape. In the CoW process, SELFA is
shows that SELFA can be applied to So the glass was able to be debonded laminated on the buffer wafer first.
higher temperature treatments such from the thin wafer without cracking it. Then, BG and back-side fabrication is
as RDL processing and soldering. It We also confirmed that the tape can be completed. After that, core chips are
means SELFA is applicable to both peeled off from the thin wafer without bonded by thermocompression bonding.
fan-out wafer-level package (FOWLP) cracking. This result shows that SELFA In our thermocompression bonding test
processing and to fan-out panel-level has a potential as a temporary bonding with a 300°C bonding head, 8 chips
package (FOPLP) processing. material applying to a very thin wafer were successfully stacked without
Glass carrier debonding from the such as one that is 20µm thick, which delamination between the buffer wafer
wafer/SELFA/glass str ucture was will be demanded in the near future for and the adhesive tape. After that, the
demonstrated with a wafer thickness 3D package applications. wafer-level molding can be applied.
of <100µm. Before carrier debonding, The surface of the wafer was also The second application idea is for
the wafer supported with glass was observed after removal of SELFA. a FOWLP, chip-first, face-up process.
treated for 1hr at 200°C in an oven and Several adherends: a Si bare wafer, Figure 7b shows process images of
then transferred onto a dicing (DC) a wafer with a polyimide passivation FOWLP using the new tape. In this
tape. The 200°C thermal treatment coat, and a wafer with bumps were process, chips are mounted on the
was a simulation of a high-temperature used. Figure 6b shows the wafer SELFA and after that, wafer-level
t r e a t m e n t l i ke C V D. A f t e r U V appearance after tape removal. No molding, BG and bumping were applied.
irradiation (254nm) the glass carrier residue of adhesive was observed on During the FOWLP process, chip shift
was manually picked up with a suction the tested wafers. during the molding step is one of the
stage (Figure 6a). The glass carrier major challenges. In our test, chip shift
was easily debonded from SELFA Application idea and subduction during molding were
without cracking the wafer. The gas The various application ideas of measured and controlled within 2µm,
that was generated from the adhesive SELFA have been proposed. In this and 1µm, respectively.
layer attached to the glass carrier article, two processes are introduced, In addition to the processes noted
enabled the glass carrier to be lifted CoW and FOWLP. Figure 7a shows above, the new tape has been used in
up from the adhesive; the contact area process images of CoW using the new several other applications and many
between the glass and the adhesive product line-ups are prepared to deal
with each customer’s process. Adhesive
strength and layer thickness can be
custom-made. Several single-sided
types utilizing the easy-peeling adhesive
design are also being readied.

Summary
In this paper, self-releasing adhesive
tape (SELFA) as a temporary bonding
material and a thin wafer supporting
system with SELFA and glass carrier
were introduced. This temporar y
bonding adhesive tape has a unique
technology for debonding carriers, which
enables self-releasing by gas generation.
At the same time, the adhesive resin
has been designed for easy peeling. By
combining these two technologies, self-
releasing adhesive tape can be applied
to 3D integration processes including
wet and high-temperature processes.
It is anticipated that this new tape will
drive further wafer thinning and support
handling of devices in the upcoming 3D
integration era.

References
1. N. Araki, S. Maetani, Y. S. Kim, S.
Kodama, T. Ohba, “Development of
E-Tec Interconnect AG, Mr. Pablo Rodriguez, Lengnau Switzerland
Phone : +41 32 654 15 50, E-mail: p.rodriguez@e-tec.com resins for bumpless interconnects and
wafer-on-wafer (WOW) integration,”
2019 IEEE 69th Elec. Comp. and Tech.

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