COVER STORY
17
topographies. In order to test this a test
structure was developed of peak to valley
of 1µm which is deliberately irregularly in
the area of the bearing.
Reliability and lifetime
In order to provide maximum benefit to
customers it is imperative that the
capsule is tight not only at the start of its Schematic drawings of an opening and closing cycle. The substrate is loaded
use but also works after hundreds of face down into the capsule and automatically closed. The unsealing process is
opening and closing cycles. To generate realised the other way round. The degree of automation is adapted to the
reliable data we developed the following technical needs of the product and/or the production phase it is in. Thicker
evaluation scenario and tested 5 capsules wafer in micro-systems technology are typically processed in a semi-automatic
of generation 5. (see below) way, while processing thin wafers (below 150µm) must be done completely
In total the test scenario was run with automated
10 capsules of the latest generation and
positive results were achieved on each
occassion. This test exceeds by far the developed and then applied. One example
typical requirements of processes like pictured at the start of the article is of an
KOH-Etching (backside protection), thin investigation via high resolution x-ray.
wafer cleaning (mechanical stabilisation,
backside protection), e-less plating Secure process
(mechanical stabilisation, backside Although seal tightness is
protection). To achieve this reliability a the main concern it is also
number of failures were deliberately of utmost importance that
included which had to be analysed and established processes can be
corrections in the design of the capsule or completed with a sealed
the opening/closing mechanisms became substrate as if it were
necessary. At certain points a combined unsealed. Comparisons of
adaptation of the opening/closing results taken in both etching
mechanism in combination with the and cleaning processes have
capsule design had to be made. To detect yielded identical results between
these potentially faulty designs a number sealed and unsealed. Additionally
of investigative methods had to be deposition processes like electroless
Passed Test Scenario for Capsules of generation 5
plating of nickel and gold have shown
supporting results in research activities at
Substrate with 1µm test structure was sealed in a Gen5 capsule the Fraunhofer Institute (IZM).
Wet-test (agitation)-> Result: No breach of sealing The development and realisation of the
Followed by new seal capsule enables customers to
200 times automated Opening/Closing cycle keep up with present process
Wet-test (agitation)-> Result: No breach of sealing manufacturing flow to a great extend
Followed by without investment in new process tools.
Exchange of bearings The usage of process tools that are
400 times automated Opening/Closing cycle normally not considered for thin wafers
Wet-test (agitation)-> Result: No breach of sealing becomes a possible alternative when
Followed by applying the capsule seal.
Exchange of bearings The tool can fulfil a number of degrees
600 times automated Opening/Closing cycle of automation ranging from a semi
Wet-test (agitation)-> Result: No breach of sealing automatic tool with manual loading to
Followed by customer adapted units that can be
Exchange of bearings integrated into other tools as an OEM-
600 times automated Opening/Closing cycle unit providing our customers to a real
Wet-test (agitation)-> Result: No breach of sealing time solution that also reduces their need
Followed by to upgrade their current tool and process
Exchange of bearings options thereby saving costs in the
600 times automated Opening/Closing cycle manufacturing process as well as
Wet-test (agitation)-> Result: No breach of sealing extending the life of current tools and
processes in the fab.
November 2008 www.euroasiasemiconductor.com
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