1. Dow Corning... We Help You Invent The Future. ™ Strategies for Wave-guides on CMOS OIC Strategies for Global Interconnect Upon CMOS Dr Terry V Clapp, Dr Jon V DeGroot jnr & Dr Ann Norris February 2004

2. Dow Corning... We Help You Invent The Future. ™ Intent 1. I will show what is driving the requirement to consider optical communications at the chip level. 2. I will show what challenges the CMOS platform offers. 3. I will offer some materials, process and waveguide propositions for these applications.

3. Dow Corning... We Help You Invent The Future. ™ The Interconnect Environment Local 2 Intermediate Up to 4 Global Up to 5 Pre-metal dielectric Tungsten plugs Copper damascene Nucleation and barrier Etch stop and dielectric cap Passivation VIA Interconnect level & number of layers

4. Dow Corning... We Help You Invent The Future. ™ Design Window The design window appears to favour dielectrics as the preferred optical material. –Spin-on glassy dielectrics would give a low-k and low temperature option. –Polymers either spun-on &/or printed might be a preferable process option in view of topology and the need for electrical connections. Polysiloxanes and perfluoropolymers both have a demonstrated process compatibility and acceptance for deployment in CMOS foundries.

5. Dow Corning... We Help You Invent The Future. ™ PWG/OIC Efforts Dow Corning working in collaboration with Gemfire and others to develop low cost OIC fabrication process as well as prototypes via photo-patterning. Multi-mode 100 x 100 micron Early attempt at single-mode 6 x 5 micron nominal dimensions

6. Dow Corning... We Help You Invent The Future. ™ Absorption <0.02dB/cm at 850 nm

7. Dow Corning... We Help You Invent The Future. ™ Spot Size / Confinement

8. Dow Corning... We Help You Invent The Future. ™ Relative versus Absolute size Say 75um pitch for the global interconnect, –at high bandwidth cross-talk is likely to be an issue, –very high speed modulation will become critical in terms of routing and power. Optical @<20um pitch for wave-guides, if, –you work in the visible –you can provide sources and receivers… in fact CW lasers off-chip with on-chip modulators seems a better architecture. For square SM buried rib wave- guides, –the core-cladding index difference determines mode confinement up to the diffraction limit, –the higher the difference, the more difficult it is to make the guide low loss, the tighter the bends you can have, –at shorter wavelengths, the core diameter is smaller, the cladding thickness can be reduced. Are mirrors vs bends the answer?

9. Dow Corning... We Help You Invent The Future. ™ Conclusions It seems clear that the optical penetration in the communications infrastructure will penetrate right down to the chip level. The demands of that environment seem to favour the adoption of technology in the visible wavebands. Materials are available but much research needs to be done to establish the boundary design rules & demonstrate the technology.

10. Dow Corning... We Help You Invent The Future. ™ Acknowledgement The contribution of my colleagues at Dow Corning is gratefully acknowledged