TCAD simulation framework for the study of TSV-device interaction
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With the reduction in transistor dimensions to a few tens of nanometers as a result of aggressive scaling, interconnect delay has now become one of the major bottlenecks to chip performance. Secondly, interconnect power and area have both become a significant part of the total chip power and area respectively. These concerns have led to an effort to find a solution that would reduce interconnect delay and leakage, while also reducing the area they occupy in a chip, so that either the chip area could be reduced, or more functionality could be incorporated within a certain area. 3D integration, i.e., stacking of various sub-systems of a chip on top of each other, enables chip-makers to achieve higher packaging efficiencies, thereby reducing system cost, while also reducing delay (and thus increasing the available bandwidth). Through Silicon Vias (TSVs) have emerged as the key interconnect technology for 3D ICs, as they enable significant reduction in delay and leakage compared to wire-bonded dies, while also occupying less area in a package. They also enable stacking of sub-systems which differ in functionality, and stacking of multiple dies. Also, unlike wire-bond, dies need not be bandwidth limited by the number of wire bonds that can be made between two levels in a stack. While TSVs offer many advantages, one of the concerns when implementing a 3D system using TSVs is the mechanisms of interaction between a TSV and a device in its vicinity. Another concern is with regards to the interaction between the TSV and its surrounding material. The purpose of this thesis is to develop a TCAD framework for process and device co-simulation of a TSV transistor system to study the various mechanisms of interaction between them, as well as between the TSV and substrate. The utility of this tool has been demonstrated by studying two mechanisms of interaction, the effect of TSV-induced stress, and the effect of TSV-device electrical coupling, on the electrical performance of bulk NMOS and PMOS transistors. The results from 3D TCAD simulations suggest that designers can scale the keep out zone (KOZ) around TSVs more aggressively, allowing for more efficient utilization of silicon area, without a drastic performance penalty.