Page 25 - Chip Scale Review_January February_2023-digital

an area i nstead of a li ne, it can
simultaneously measure photoresist
thickness and bump height. There
are geometrical limitations on the
photoresist and the bump to enable
accurate bump height calculation.
Currently, the photoresist must be
at least 45µm-thick to distinguish
between direct ref lection from the
photoresist surface and ref lection
from the substrate. The bump height
must be less than the photoresist
thickness but not too far below it.
The maximum difference between the
Figure 5: Measurement of bump height before photoresist stripping, using light refracted through the bump and photoresist thickness – the
photoresist to determine the photoresist thickness and calculate bump height above the wafer surface. depth below photoresist, as shown in
Figure 5 – is approximately twice the
image free from distracting artifacts. measured to determine the substrate width of the pillar. If the aspect ratio
Beyond the visual appeal (see Figure height. A portion of the incoming light between the depth and the width is
4), the MRS system enables more reflects directly off the top surface too high, the light will deflect off the
precise heig ht measu rement s. It of the photoresist. The rest of the sides of the photoresist rather than
is currently capable of measuring light passes through the photoresist reflect directly to the CMOS detector.
bumps 25µm in diameter with 3µm to the wafer surface and is refracted Bu m p h e i g h t u n i f o r m i t y
lateral resolution and 0.05µm vertical as it exits the photoresist. Given the m e a s u r e m e n t s f r o m 3D f r i n g e
(Z height) resolution. photoresist index of refraction and data p r o j e c t i o n a r e c o n s i s t e n t w i t h
from the sensor, the system measures d a t a f r om a r efe r e n c e c o n fo c a l
Advantages of fringe projection the photoresist thickness. measurement system. The reference
with MRS Because the imaging system scans system is highly accurate but takes
Fringe projection technology offers
greater throughput compared to line
scan triangulation, in part because
it i mages an enti re area at once
rather than line by line. The field of
view and frame rate are important
parameters. A system with multiple
cameras and projectors operating in
parallel at high frame rates allows the
technology to scale.
O u r n e w f r i n g e p r o j e c t i o n
®
technology is rapid—collecting a Elevate Ni 5950
2D scan of the wafer and height Boric Acid Free Nickel
measurements of 3D features in a
single pass. The system inspects Exceptionally stable,
100% of the bumps on a 300mm wafer versatile, sulfamate plating
in minutes. By analyzing 75 million
points every second, it achieves a
throughput of greater than 25 wafers • Boric acid free
p e r hou r. T he f r i nge proje ct ion • All liquid components
system images copper pillars before • Very stable electrolyte
the photoresist is stripped, either • Superior coplanarity
directly after copper electroplating • Low-stress semi-bright deposit
or after applying a solder cap but • Optimum deposit up to 10 ASD
before reflowing the solder. This is a • Versatile - can be used in all types of
critical advantage because it provides applications requiring nickel
diagnostic data on the copper plating
and solder bumping processes. This
allows for process correction if the
plating is out of tolerance.
As the wafer is scanned at high
s p e e d , phot o r e si s t t h ick n e s s i s www.technic.com

2/23/2022 3:16:50 PM
Chip Scale Review - Elevate Ni 5959v2.indd 1
Chip Scale Review - Elevate Ni 5959v2.indd 1 2/23/2022 3:16:50 PM
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