PhD - Leuven | More than two weeks ago
Current Memory-on-Logic applications focus on the partitioning of either complete memory sub-systems (so memory arrays together with the memory controller logic) or the memory macros (the control logic remains on the logic die). In most of the designs the second solution exhibits better power, performance, area (PPA) but also cost, since the memory wafer processing can now be optimized though simplification of the BEOL and FEOL processing steps. The downside of the approach is that the number of 3D connections increases significantly. However, current Face-to-Face, Copper-to-Copper Hybrid bonding techniques allow to integrate 3D structures with a sub 1um pitch, which seems to be more than sufficient in partitioning intermediate cache memory layers even in advanced CMOS nodes (e.g. iN5). Such 3D integration technology motivates yet another memory partitioning scenario in which only bit-cell arrays are moved to another die. We expect that the number of 3D pins increases one order of the magnitude, however the expectations are that further PPAC benefits could be achieved. In this PhD the candidate will work on the design enablement of bit-array memory partitioning using current state of the art 3D implementation tools available at imec. Once the flow is ready, the required views (timing, power, geometry) for implementation of the bit-array partitioned memories will be proposed. Exhaustive SoC-level 3D place & route experiments will be carried on to provide in-depth analysis of different trade-offs linked to the proposed approach and when compared to more traditional Memory-on-Logic implementation. Cost aspects will be also covered using the existing cost models that need to be adapted for the above proposed partitioning scheme.
Required background: Masters in Electrical Engineering with CMOS design background, experienced in computer architecture
Type of work: Design enablement and SoC level characterization of bit-array memory partitioning in 3D ICs
Supervisor: Dragomir Milojevic
Daily advisor: Shairfe Muhammad Salahuddin, Rongmei Chen
The reference code for this position is 2021-044. Mention this reference code on your application form.