Ultrathin chip fab process ready to ramp: IEDM presentation - Advanced Packaging
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Ultrathin chip fab process ready to ramp: IEDM presentation

(December 8, 2010) -- During the IEEE International Electron Devices Meeting (IEDM 2010), held this week in San Francisco, researchers from the Institute for Microelectronics Stuttgart (IMS CHIPS), led by Joachim Burghartz, presented an improved version of their Chipfilm technology introduced in an IEDM 2006 Late News paper. The researchers now have a manufacturable process technology.

During the past three years IMS CHIPS developed this process in cooperation with semiconductor foundries operated by Robert Bosch GmbH, Micronas and Telefunken Semiconductors, and other partners within a large research project funded by the German federal ministry BMBF. Engineering for a wide process window was one particular focus during the Chipfilm technology development for the past three years. The researchers have finally succeeded in designing the array of anchors and the individual anchor structure for a process window suitable for industrial manufacturing.

Differently from wafer thinning techniques, the Chipfilm technology is based on narrow cavity formation underneath the chip areas on wafers above which the target chip thickness is set by precise epitaxial growth of silicon. As a result, ultra-thin chips (<20 μm) can be realized with excellent uniformity control across the wafer and from wafer to wafer. Such Chipfilm wafers can be used for the integration of microelectronic circuits like any conventional wafer substrate.

After circuit integration and etching of trenches along the chip edges, the ultra-thin chips can efficiently be detached by breaking residual anchors underneath the chips. Those anchors need to be designed on the one hand to provide high mechanical stability during wafer processing and on the other hand for fracturability after the trench etching at the end of the process sequence. Anchor fracture for chip detachment can be assisted by externally induced stress from bending the wafer to widen the process window.

In their presentation at IEDM 2010, they also show that the Chipfilm dies exhibit superior mechanical stability. A 20μm thin chip can be bent to a radius as small as 0.8mm, making Chipfilm technology particularly suited for applications in flexible electronics. But, due to the extendability to very small thickness with excellent thickness control, the Chipfilm technology may also be applicable for chip stacking in three-dimensional (3D) integrated systems. As such, the paper by IMS CHIPS is presented in the technical session "Advanced 3D Integration" at IEDM 2010.

The Institut für Mikroelektronik Stuttgart (IMS CHIPS) carries out industrial-oriented microelectronic research in silicon technology, customized circuits (ASIC), photo lithography and image sensor technology as well as being involved in professional development. Learn more at www.ims-chips.com

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