Fan-in WLCSP matures, what's next? IMT on the role ... - I-Micronews

F E B R U A R Y 2 0 1 0 i s s u e n ° 1 4
N e w s l e t t e r o n 3 D I C , T S V , W L P & E m b e d d e d T e c h n o l o g i e s
TSV <strong>in</strong>tegration <strong>in</strong> their first BSI sensor. As before, an epoxy is used both to
attach a front glass to the light receiv<strong>in</strong>g side of the sensor, and also as part of
the redistribution layer build up.
While arguably not as elegant as TSVs, the ShellOP packag<strong>in</strong>g provides
nearly the same advantages, and has proven to be a highly manufacturable
approach for 200 mm CIS wafers. For now, OmniVision/TSMC are happy to
not add TSV <strong>in</strong>tegration costs to the already significant <strong>in</strong>vestment it took
to get BSI <strong>in</strong>to mass production. It is worth mention<strong>in</strong>g that the real world
examples are a snapshot of current production. TSMC developed its TSV
technology <strong>in</strong> parallel, but did not <strong>in</strong>sert it <strong>in</strong>to production, <strong>in</strong> part because
of mechanical stress issues impact<strong>in</strong>g wafer yield. TSMC estimates a 5% to
15% gross die per wafer yield <strong>in</strong>crease (compared to exist<strong>in</strong>g sidewall CSP)
is possible through TSV <strong>in</strong>tegration. The sensor area reduction comes from
elim<strong>in</strong>at<strong>in</strong>g the lateral extensions and mov<strong>in</strong>g the circuitry under the pads
(CUP), form<strong>in</strong>g a vertical <strong>in</strong>terconnect.
Look<strong>in</strong>g at the competitive landscape, the simplest option was executed by
Sony, who was first to market with a SOI-based BSI sensor. The relatively
relaxed form factor constra<strong>in</strong>ts of its camcorder CIS enabled a simple
backside wire bond<strong>in</strong>g approach. While effective for the application, this
approach would not be an option for a camera phone module. With<strong>in</strong> the
realm of camera phone modules, Chipworks has analyzed front illum<strong>in</strong>ated
image sensors us<strong>in</strong>g TSVs fabricated by Toshiba and STMicroelectronics.
Both companies are <strong>in</strong> BSI development, and will likely go straight to BSI +
TSV. Several other CIS companies have published papers and/or have been
awarded patents for both BSI and TSV implementations. One th<strong>in</strong>g is certa<strong>in</strong>:
to vary<strong>in</strong>g degrees all CIS IDMs and foundries will be forced to evolve their
packag<strong>in</strong>g solutions. TSVs may not be a necessity at the moment, but <strong>in</strong> the
quest for a 3D <strong>in</strong>tegrated imager, their <strong>in</strong>tegration seems <strong>in</strong>evitable.
Lithography for 3D-ICs and CMOS image sensors
Wafer-to-wafer and chip-to-wafer bond<strong>in</strong>g
www.chipworks.com
Temporary bond<strong>in</strong>g and debond<strong>in</strong>g for th<strong>in</strong> wafer
process<strong>in</strong>g
Ray Fonta<strong>in</strong>e has been a process analyst at Chipworks s<strong>in</strong>ce
2001, specializ<strong>in</strong>g <strong>in</strong> image sensors. He has authored and
technically reviewed numerous image sensor process review
(IPR) reports.
Chipworks is the recognized leader <strong>in</strong> reverse eng<strong>in</strong>eer<strong>in</strong>g and patent
<strong>in</strong>fr<strong>in</strong>gement analysis of semiconductors and electronic systems. The
company’s ability to analyze the circuitry and physical composition of
these systems makes them a key partner <strong>in</strong> the success of the world’s
largest semiconductor and microelectronics companies. Intellectual
property groups and their legal counsel trust Chipworks for success <strong>in</strong>
patent licens<strong>in</strong>g and litigation – earn<strong>in</strong>g hundreds of millions of dollars
<strong>in</strong> patent licenses and sav<strong>in</strong>g as much <strong>in</strong> royalty payments. Research &
Development and Product Management rely on Chipworks for success
<strong>in</strong> new product design and launch, sav<strong>in</strong>g hundreds of millions of dollars
<strong>in</strong> design and earn<strong>in</strong>g even more through superior product design and
faster launches. Headquartered <strong>in</strong> Canada, Chipworks ma<strong>in</strong>ta<strong>in</strong>s offices
<strong>in</strong> the USA, Japan, Korea, and Taiwan.
14