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Sub-imaging techniques for 3D-interconnects on bonded wafer pairs

: Kong, L.W.; Krueger, P.; Zschech, E.; Rudack, A.C.; Arkalgud, S.; Diebold, A.C.


Zschech, E. ; American Institute of Physics -AIP-, New York:
Stress-induced phenomena in metallization. Eleventh International Workshop on Stress-Induced Phenomena in Metallization 2010 : Bad Schandau, Germany, 12 - 14 April 2010
Woodbury, N.Y.: AIP, 2010 (AIP Conference Proceedings 1300)
ISBN: 978-0-7354-0855-5
ISSN: 0094-243X
International Workshop on Stress-Induced Phenomena in Metallization <11, 2010, Bad Schandau>
Conference Paper
Fraunhofer IZFP, Institutsteil Dresden ( IKTS-MD) ()

The semiconductor industry's ability to follow Moore's law to continue to increase the number of components on integrated circuits is increasingly difficult. One way to improve the product performance even at decreased footprint is the use of 3D interconnects which stacks multiple chips in a single package. This new technology for connecting chips overcomes some of the limitations of 2D interconnects. For example, 3D interconnects significantly reduce interconnect delay and improve clock distribution. At the same time that research into 3D technology such as Through Silicon Vias (TSVs) is advancing quickly, the microscopy techniques used in the evaluation of TSV must also advance in capability. Void inspection after copper plating, defect detection and overlay measurements after wafer bonding are challenging. Microscopy techniques for which silicon is opaque such as scanning acoustic microscope (SAM) and confocal infrared microscope (IR) are capable of inspecting the in terface between bonded wafer pairs, while high resolution X-Ray techniques are used to detect voids in TSVs. Initial work was done to determine the limitation of these techniques. Four pairs of bonded wafers were prepared at different thicknesses (100, 200, 300 and 400 m) to evaluate the effects of wafer thinning using acoustic and infrared microscopy techniques. SAM was able to resolve the 20 m alignment structure with 300 MHz transducer on 300 mm wafer pair, while IR has sub-micron resolution for all bonded wafers. This paper discusses the current status of SAM, IR microscopy and XRM in terms of their application to process metrology for 3D interconnects.