The Science & Technology department of IBM Research - Zurich is active in three areas that are important for the future development of servers:
- chip-level thermal management,
- optical interconnects, and
- heterogeneous integration.
These topics are currently being investigated separately, but there is a clear trend toward their integration in a future stacked chip with electronic and optical components using interlayer liquid cooling.
Chip-level thermal management
One of the main challenges to the continued improvement of integration density of information processing equipment is the removal of dissipated heat. This is caused by the increased power density resulting from smaller transistors and faster clock speeds. Thermophysical research helps to improve heat transfer from the transistor junctions through the chip and interfaces, and eventually to the ambient air or the coolant circuit. Using microfabrication techniques, we are creating interfaces and coolers with high aspect ratio patterns. Hierarchical nested structures draw on principles ubiquitous in nature to reduce the pressure drop that occurs when paste is squeezed out of gaps, thus creating high-performance thermal interfaces, as well as for liquid cooling with many tens of thousands of capillaries or jets.
As the performance of microprocessors continues to increase, the data flow to and from the processors becomes an increasingly predominant bottleneck for overall system performance. Optical data transmission has successfully replaced electronic data transmission in most link classes greater than 10 meters due to a higher bandwidth × length product, higher density, as well as cost and power savings by avoided repeaters. At the IBM Research - Zurich, a generic technology platform for intra-system optical interconnects is being developed, in particular
- system-level opportunities for optical links,
- overall chip-to-chip link architecture,
- CMOS drivers with maximum speed at minimal area and power consumption, and
- the interface between the electrical and the optical domain (opto-electronic packaging).
Heterogeneous integration designates technologies that can be integrated in one device. In microelectronic and microsystems, such multi-technology devices refer to systems-on-chip (SoCs) or systems-in-package (SiPs). This allows optimization of the system at a higher hierarchical level so that traditional systems are outperformed. SoCs and SoPs also have a cost advantage due to simplified packaging and smaller system form factors. Examples of SoCs are embedded DRAM in ASIC, dynamic graphic processing in multicore processor chips, and processors with various peripherals. Integration of MEMS and/or optoelectronic devices on CMOS is an example where considerable research and development has been done.