Professor David Pan of UT ECE has been awarded a grant from the National Science Foundation (NSF) for his research on Design for Manufacturability for 3D ICs with Through Silicon Vias. This is a collaboration research project with Prof. Sung Kyu Lim at Georgia Tech. 3D IC is gaining a lot of momentum in industry, and this project will study key DFM issues which are not yet addressed.
Through-Silicon-Via (TSV) provides the possibility of arranging heterogeneous components across multiple dies at a fine level of granularity in 3D ICs. This can result in significant decrease in the overall wire length, delay, power, and form factor. Primarily due to their large size compared with other layout objects, however, TSVs cause significant non-uniform density distribution in various layers. This density issue is expected to cause trouble during chemical mechanical polishing (CMP) and require TSV-aware solutions. In addition, the CTE (coefficient of thermal expansion) mismatch between TSV copper and silicon causes significant thermal mechanical stress to the devices nearby during TSV manufacturing and circuit operation. This in turn affects the timing and power characteristics of the devices. The mechanical reliability of the substrate and devices are also affected by TSVs. However, little is known on what design tool and methodology changes are required to improve the manufacturability of TSV-based 3D ICs. This project would investigate three key DFM/DFR areas specific to 3D IC integration, namely, TSV-induced stress effect and its impact to the overall circuit timing and power, TSV impact to CMP and lithography, and TSV-induced reliability. Successful completion of the project would help us to gain in-depth understanding of manufacturability and reliability issues with 3D ICs and TSV technology and develop effective physical design solutions to overcome these issues. The proposal calls for a very strong collaboration between the researchers from the manufacturability and reliability modeling, simulation, and validation area and the researchers from circuit and physical design area for 3D ICs.