Maxwell Room (57-124 EIV)

10:30 am to 11:30 am


Dr. Hisashi Kino

Title: “Effect of microbump-induced local bending stress on transistor
performance in 3D IC under thermal load”

Abstract: Three-dimensionally stacked ICs (3D ICs) consist of several
materials such as Si substrates, metals for TSVs and microbumps, organic
adhesives, and so on. These materials generate a serial issue of
coefficient of thermal expansion (CTE) mismatch. On the other hands,
operating circuits generate heat on Si substrates. Both the CTE mismatch
and heat generation during circuit operation induce local stresses
attributed to the organic adhesives injected around metal microbumps.
Analytical results of effects of adhesive expansion/shrinkage on
transistor performances using finite element method (FEM) simulation and
transistor characteristics measurement will be introduced.

Mr. Seiya Tanikawa (Ph.D. candidate)

Title: “Impact of local stress in 3D stacking process on memory
retention characteristics in thinned DRAM chip”

Abstract: Local stresses are induced by CTE mismatch among Cu/Sn bumps,
organic adhesives, and Si substrates in 3D chip stacking processes. The
effect of the local stresses on memory retention time has been
characterized in detail. In particular, we investigated in-plane local
bending stress distribution before and after Si thinning of DRAM chips.
The retention time of memory cells in a 200-µm-thick DRAM chip having
planar-type capacitors was largely changed after Cu/Sn bump bonding and
the subsequent underfill curing. After thinning of the DRAM chip down to
40 µm, the retention time of the memory cell was not significantly
changed in the whole area even on the Cu/Sn bumps due to the shift of
the distance from the neutral surface.

Date(s) - Apr 18, 2016
10:30 am - 11:30 am

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