Page 57 - ChipScale_Mar-Apr_2021-digital

a tilted platform. Gravity then causes
the panel to slide down. The panel,
when moving, is not in contact with the
handling robot; therefore, the elevated
temperature is kept uniform across the
panel while being transported. The
mechanism to be applied for panel-level
debonding is baselining the effectiveness
on a 300mm format contactless transport.
Thermal control
A round 300mm thermal chuck surface
Figure 9: Defined test vehicle based on the panel layout: a) single matrix; b) 2x2 matrix; and c) single matrix is proven to be within the ±2°C for 200°C
with rectangular die. (tighter range on lower temperature),
which is above the release temperature
Large-panel thermal debonding thermal imbalance, causing the part in range of 175-195°C of the commercially-
I n ther mal debondi ng (Figure contact to shrink/contract resulting in available thermal release tapes.
3), process temperat u re, timing, warpage (Figure 4). A previously presented paper [3] showed
and handling are defined as critical Handling is more complicated with the effects of thermal nonuniformity
factors to ensure high yield. Panel a larger area. The end effector design, on die shift. Wafers subjected to a high
handling is essential to ensure no weight, and size of the panel will nonuniformity chuck vs. a chuck of
excursion occurs. This is the first step contribute to the overall warpage and the 186°C ± 1°C showed significant yield
where panel fragility (thickness, die stability of the panel when transported. performance (Figure 7). The wafer in
placement layout, etc.) and weight will A common handling mechanism is pick- Figure 7a showed high nonuniformity,
be a factor to consider in defining a and-place using a robot with a customized while the wafer in Figure 7b has ±1°C
handling mechanism. end effector (Figure 5). uniformity. The corresponding die shift
Thermal control needs to be robust Another method is the air cushion showed that with higher nonuniformity
to maintain adequate uniformity across mechanism (Figure 6), which is the die shift is larger in magnitude
a larger surface. The thermal sensitive contactless transport whereby the panel compared to a chuck with high thermal
tape needs to activate across the entire is lifted with controlled air pressure on uniformity [3] (Figure 8).

Figure 10: Temperature profile of the chuck measured at: a) 100°C; b) 150°C; and c) 200°C.

surface uniformly to eliminate not only
potential cosmetic defects, but also
excursion. The mechanical separation
of the carrier and the panel can only
happen when the thermal release tape
has been fully activated uniformly
across the whole surface.
Hand l i ng and t ranspor t. T he
handling method of molded wafers is
critical in minimizing handling-induced
warpage [2]. With a high-temperature
molded wafer, any introduction of
low-temperature objects will create Figure 11: Warpage profiles for: a) sample 1; and b) sample 2.

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