Mario J. Interrante

Three-dimensional silicon integration

Three-dimensional (3D) silicon integration of active devices with through-silicon vias (TSVs), thinned silicon, and silicon-to-silicon fine-pitch interconnections offers many product benefits. Advantages of these emerging 3D silicon integration technologies can include the following: power efficiency, performance enhancements, significant product miniaturization, cost reduction, and modular design for improved time to market. IBM research activities are aimed at providing design rules, structures, and processes that make 3D technology manufacturable for chips used in actual products on the basis of data from test-vehicle (i.e., prototype) design, fabrication, and characterization demonstrations. Three-dimensional integration can be applied to a wide range of interconnection densities (<10/cm2 to 108/cm2), requiring new architectures for product optimization and multiple options for fabrication. Demonstration test structures, which are designed, fabricated, and characterized, are used to generate experimental data, establish models and design guidelines, and help define processes for future product consideration. This paper 1) reviews technology integration from a historical perspective, 2) describes industry-wide progress in 3D technology with examples of TSV and silicon-silicon interconnection advancement over the last 10 years, 3) highlights 3D technology from IBM, including demonstration test vehicles used to develop ground rules, collect data, and evaluate reliability, and 4) provides examples of 3D emerging industry product applications that could create marketable systems.

3D chip stacking with C4 technology

Three-dimensional (3D) integration technology promises to continue enhancing integrated-circuit system performance with high bandwidth, low latency, low power, and a small form factor for a variety of applications. In this work, conventional C4 (controlled-collapse chip connection) technology is studied for robust interconnection between stacked thin chips. Various solder hierarchies to enable 3D chip stacking and packaging are investigated. Examples are presented to compare stacking schemes with sequential and parallel reflow. Chips as thin as 90 µm are stacked using conventional chip-placement and reflow processes, and the associated process challenges are investigated and discussed. Warpage of the thin chips is measured on various substrates. Rework of the chip stack has also been demonstrated through a temporary chip attachment operation, and the scalability of reworkable C4 is investigated.

Three-Dimensional Chip Stack With Integrated Decoupling Capacitors and Thru-Si Via Interconnects

In this letter, the integration of CMOS-compatible thru-Si via (TSV) interconnects with deep-trench decoupling capacitors is demonstrated. Reliability test is performed with a 65-nm CMOS test chip on top of a 3-D Si interposer chip that contains 10 000 TSV interconnects. Multilayer stacking is also demonstrated, and capacitance density of 280 nF/mm2 is achieved with two-layer Si interposer chip stacks.

Engineering change (EC) technology for thin film metallurgy on polyimide films

Engineering change in multichip modules such as the IBM Thermal Conduction Module (TCM) requires making new nets on the top surface of the module. This is done either to repair opens or shorts in the internal nets or to correct design errors. Since the trend in multichip packaging in the high end is towards thin-film wiring with polyimide as the dielectric, wire-bond and laser delete processes compatible with thin-film metallurgy on polyimide films are required to carry out engineering change. The authors describe the results of a technology-development effort to optimize these processes on a metal/polyimide thin-film structure.<<ETX>>

Reliable through silicon vias for 3D silicon applications

The use of through silicon vias (TSVs) is required to implement 3D chip stacking technology. This work explores a method to fabricate highly reliable TSVs that is compatible with CMOS processing. The key feature of the TSVs is a redundant tungsten bar with a high temperature thermal oxide insulating liner. Care must be taken when exposing the TSVs from the back side so that material is not left on the surface that can cause a leakage path to the silicon wafer. TSVs were produced with that had no fails through standard JDEC testing.