Zukunftstechnologie Dünnglasbasierte elektrooptische. Research Center of Microperipheric Technologies

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1 Zukunftstechnologie Dünnglasbasierte elektrooptische Baugruppenträger Dr. Henning Schröder Fraunhofer IZM, Berlin, Germany Today/Overview Motivation: external roadmaps High Bandwidth and Channel Density Power Efficiency glasspack - Packaging Concept Module Integration in PCB Single Mode Waveguides for Si Photonics WDM integration Photonic integration using thin glass foils: glasspack Glass compatible Technologies: Optical Waveguides Processing and Interconnecting PCB Lamination Electrical Wires and Feed Throughs Summary

2 Trends in HPC performance Source: Dorren, Fotonica 2011, Utrecht Roadmap Copper Optics and Silicon Photonics Source: INTEL Dr. M. Paniccia

3 Why planar integrated optical chip-to-chip interconnects? High bandwidth (beyond 10 Gbps) copper wires becoming challanging Silicon photonics components are arising Intel: 1 st 50 Gbps Si photonics link PD, modulators, MUX/DEMUX available Source: es/2010/ comp_sm.htm#story For conjunction of tele- and datacom: optical communication within any compute platform: Long interconnect length and high channel density can be achieved New architectures are possible No fiber packaging in the very short range Power efficiency of e/o systems potentionally better than in electronic systems Data transport is the energy problem 200 x more energy needed to transport a bit from a nearest neighbor chip than to operate on it: Energy needed for a floating point operation ( pj/bit) Energy needed for (electronic) datatransport on card(210 pj/bit) In a big system (50 meter diameter, multistage network with routers and multiple transceiver hops) the factor may be 1000x Optics has improved bandwidth distance product compared to electronics Use optics for data transport, not for processing!! Sources: DARPA/IPTO study, by Peter Kogge, et. al.: Alan Benner (IBM), Key note at IEEE Winter Topical Meeting Mallorca (2010) Dorren, Fotonika 2011, Utrecht

4 Where Optics in HPC? On the chip between cores: Power too high, distance too low, electronics can do this better! On a board, for communication between chips No Perhaps Perhaps for CPU/DIMM interconnect but 3D packaging will be needed Electronics also makes progress Optics might be winner due to bandwidth density and not due to lower power dissipation For communication between boards Yes Distance is relatively high high bandwidth density Is already starting off in HPCs Why not optics to the CPU? For communication between racks Already today using active optical cables in HPCs and DCs Yes Sources: Dorren, COBRA, Fotonica 2011, Utrecht

5 EOCB and Optical Backplane Glass based active interposer! 4 x 10 Gbps tx and Rx on glass based interposer New results: Chip-to-chip communication by optical routing inside a thin glass substrate, L. Brusberg, N. Schlepple, H. Schröder Fraunhofer IZM, Berlin, Germany ECTC 2011, Session 18 Glass Packaging Concept glasspack TGV glass interposer Single-mode optical high-speed interconnects Platform for photonic integrated circuits (PIC) Embedded glass core layer in the electricaloptical circuit board (EOCB) Fiber Connector New results: Glass Panel Processing for Electrical and Optical Packaging, H. Schröder, L. Brusberg, N. Arndt-Staufenbiel, J. Hofmann, S. Marx Fraunhofer IZM, Berlin, Germany Technische Universität Berlin, Germany ECTC 2011, Session 14 EOCB Interposer PIC Lens TGV Interlayer beam Mirror Waveguide Laser Dia

6 Single-mode graded index glass waveguides for boardlevel WDM optical chip-to-chip communication Features SM waveguides in planar glass foils passive and active submicron optical coupling CWDM microoptical automated assembly PCB integration Single mode fiber Future trend Photonic integrated circuit VCSEL Interposer Board Waveguide Mirror Lens Two step thermal ion-exchange technology State-of-the art - Planar integration in glass foils Fiber Transceiver IC Interposer - Low propagation loss (0.2 - Single mode in telecom wavelength - WDM compatible Brusberg - Mode field matches to SMF Refractive index Board Dimension [µm] Thin glass Waveguide Refractive index Dimension [µm] 2D refractive index scan (RNFmeasurement) SM-Waveguide Technologies Glass surface Waveguide Waveguide Glass end-face Microscope picture of end-face with two stimulated waveguides having pitch of 250 µm Insertion loss of 9cm waveguide sample

7 High speed laser structuring for TGV: Trough Glass Via 500 µm best result at the moment with current IZM equippment CO 2 -Laser T pulse = 75 µs quasi-cw λ = nm Diameter: d in = 71 µm d out = 46 µm Pitch: p = 500 µm Speed: < 0.3 sec/hole Low stress Reflow compatible E/O System Integration Concept Glass Panel Processing glasspack module integration TIA IC Glass Interposer PD VCSEL Driver IC Glass Interposer EOCB Embedded Optical Waveguide Layer

8 MM-Waveguide Technologies Multi-mode large panel waveguide technology: etch mask patterning Patterned aluminum diffusion mask on 210 mm 297 mm glass panel ready for 1 st ion exchange process. diffusion mask detail with waveguide bended splitters, patterned by LDI pixel exposure with Orbotech Paragon 9000 and mask exposure (right, waveguide pitch is 250 µm). Development of large panel wave guide processing by ion exchange in thin glass foil Work station for industrial fabrication of large panel opto foils

9 Optical waveguide technology: Ion-exchange Two step thermal processing planar optical waveguides on both surfaces 2x12 channel waveguide array Thin glass (300µm) Planar optical waveguides Waveguide Thin glass surface MM-Waveguide Technologies

10 Lamination in PCB base material Delaminated glass core build-ups using FR4 (left). The delamination is caused by lateral glass damaging (right) (figures courtesy of Contag GmbH). Ultrasonic image of 200 mm x 80 mm thin glass foil laminated in between RCC foils. laminated thin glass sheet in glass core build-up using FR4. Size is 210 mm 297 mm with small frame. The 3 open releases are milled and show no delamination after time (figures courtesy of Contag GmbH). Milling for optical interfaces Optical photograph of milled (but not polished) glass edges with damaging (glass surface built-up, left) and without (glass core built-up, right) (figures courtesy of Contag GmbH)

11 Via drilling Optical photograph of a laser drilled via hole of about 300 µm in diameter at laser inlet (left) and about 220 µm at laser outlet (right) side (figures courtesy of Contag GmbH). Optical photograph of a via hole of about 300 µm diameter (glass surface built-up). Benefit from thin glass based SiP and board integrated e/o Modules CTE close to Si and III-V-components Acceptable ε r and tanδ comparable to ceramics but lower surface roughness (R a < 1nm) resulting in lower attenuation at high frequencies because of thin film processed wires Through glass vias do not need passivation layer in contrast to silicon No dimensional instability and necessity for fire retargends in contrast to organic substrates Transparent material PCB integration of thin glass foils with integrated optical multimode waveguides already demonstrated Same optical integration technology on board and module level causes optimal waveguide mode matching

12 Langfristiger Technologietrend glasspack Integration Roadmap Data rate Tbps electrical optical glass based integration Xyratex Gbps KAPAREL Corp. Intra-Chip Chip-to-Chip Board-to-board Rack-to-Rack MAN, WAN µm mm cm m km Interconnection length Take home Glass based Photonic Packaging glasspack-concept glasspack is a novel packaging concept based on using thin glass as substrate material for high-data transmission applications glass is green material with excellent optical and electrical properties Suitable for large panel photonic packaging Energy consumption optical vs. electrical for high bandwidths and longer signal lengths optical will definitively be more energy efficient than electrical high speed signals the crossover point where optical interconnects save energy should already be in the region of backplane interconnects or shorter with Si Photonics GlassPack technologies at Fraunhofer IZM Optical waveguides and interconnects (lenses, mirrors) Through glass vias (TGV) Thin film processing Component assembling