Silicon Photonics: an Industrial Perspective -...

Silicon Photonics:

an Industrial Perspective

Antonio Fincato

Advanced Programs R&D, Cornaredo, Italy

OUTLINE 2

A. Fincato - Silicon Photonics: an Industrial Perspective 27/10/2016

• Introduction

• Silicon Photonics Concept

• 300mm (12’’) Photonic Process

• Main Silicon Photonics Devices

• Future Evolution

• Conclusion

OUTLINE 3


• Introduction





• Conclusion

Silicon Photonics Main Application Areas 4


High Performance Computer Data Center Access Network

Typical Losses of Electrical

Transmission Lines @ 15GHz

RF Cable 1dB/m

Backplane 3 dB/cm

Board 1 dB/cm

Intrachip 1 dB/mm

Typical Losses of Optical Transmission

Lines @ 1310nm

SM Fiber 0.5 dB/km

Si waveguide 0.2-2 dB/cm

SiN waveguide 0.1dB/cm

SiO2 waveguide < 0.1 dB/cm

The Zettabyte Era

• By the end of 2016, global IP traffic will

reach 1.1 ZB per year, or 88.7 EB per

month

• By 2020 global IP traffic will reach 2.3

ZB per year, or 194 EB per month

• Overall, IP traffic will grow at a

compound annual growth rate (CAGR)

of 22% from 2015 to 2020

5

The Zettabyte Era: Trends and Analysis, July 2016 - White Paper - CISCO

http://www.cisco.com/c/en/us/solutions/collateral/service-provider/visual-networking-index-vni/vni-hyperconnectivity-wp.html


http://www.cisco.com/c/en/us/solutions/collateral/service-provider/visual-networking-index-vni/vni-hyperconnectivity-wp.html

Global Data Center IP Traffic:

Three-Fold Increase by 2019 • Annual global data center IP traffic will

reach 10.4 ZB (863 EB per month) by

the end of 2019, up from 3.4 ZB per year

(287 EB per month) in 2014.

• Global data center IP traffic will grow 3-

fold over the next 5 years. Overall, data

center IP traffic will grow at a compound

annual growth rate (CAGR) of 25% from

2014 to 2019.

• By 2019, 86% of workloads will be

processed by cloud data centers; 14%

will be processed by traditional data

centers.

6

Cisco Global Cloud Index: Forecast and Methodology, 2014–2019 - White Paper - CISCO

http://www.cisco.com/c/en/us/solutions/collateral/service-provider/global-cloud-index-gci/Cloud_Index_White_Paper.pdf


Zettabyte per Year

http://www.cisco.com/c/en/us/solutions/collateral/service-provider/global-cloud-index-gci/Cloud_Index_White_Paper.pdf

Supercomputing Power Growth

• Exponential growth of

supercomputing power as recorded

by the TOP500 list

7

TOP 500

https://www.top500.org/statistics/perfdevel/


https://www.top500.org/statistics/perfdevel/

8


International Standard Requests

Speed will increase Size and power will decrease

http://www.ethernetalliance.org/roadmap/

OUTLINE 9


• Introduction





• ConclusionTotal internal reflection is a special optical

condition in which optical rays cannot escape

the material in which they are traveling.

John Tyndall

Optical Properties of Silicon in Near IR (1) 10


Indirect Bandgap

No laser source

Centro-Symmetric Crystal

No Electrooptic effect

Momentum

not conserved

Optical Properties of Silicon in Near IR (2) 11


Wavelength (nm)

VISIBLE

Photodetectors

Transparency

Wavelength (nm)

Ab

so

rptio

n c

oe

ffic

ient (c

m-1

)

Silicon Absorption Coefficient

Electronic-Photonic Monolitic Integration (1)

Samsung, OFC 2013IBM, IEDM 2012Luxtera, ISSCC 2006

<100nm

0.1 µm 0.02 µm

<10nm

1 µm

BO

XS

OI

200-500nm

Photonics PD-SOI or SOI-FinFET UTBB-FDSOI Bulk

28nm,14nm,10nm 55nm, 28nm,20nm22,14,10 nm FinFET

SOI 130nm,90nm,45nm

BUT

12


CMOS 130nm CMOS 90nm DRAM

13

Photonics Electronics

Local Photonics Substrate creation

Samsung, OFC 2013,GFP2013Micron, VLSI tech. 2014IHP, GFP 2013

Photonics Electronics

Integrate CMOS on Photonics Substrate

Luxtera, ISSCC 2006,IBM, IEDM 2012

Need a re-development of the CMOS technology Cost issues , especially with Advanced

Technologies (55nm and below)

Electronic-Photonic Monolitic Integration (2)


143D Integration Strategy of ST


Opto-Electronic System = Photonic IC + Electronic IC

Opto-Electronic IC

Electronic IC:CMOS or BiCMOS

Cu pillar

Independent evolution for optimization of technology platform

(process flow & design environment)Opto-Electronic

System

Photonic IC

Cu pillar

15

EIC PIC

EIC

PIC

40µmPIC

EIC

3D integration: F2F Assembly


OUTLINE 16


• Introduction





• Conclusion

PIC25G Silicon Photonics Technology Platform 17


Joint Development started 2012

l Type Function

l=1

31

0n

m &

14

90

nm

Optical Passives

Multimode waveguide

Single Mode waveguide

Curved waveguide

Tapered waveguide

90°C Bend (R=40µm)

Directional coupler – Split ratio 1÷99%

Y-junction: Splitter

Fiber (8°) Single Polarization Grating Coupler (TX-out)

Laser (13.2°) Single Polarization Grating Coupler (TX-in)

Dual Polarization Grating Coupler (RX-in)

WG termination

Optical ModulatorsHigh Speed Amplitude Modulator – Vcc=1.8V-2.5V

Phase Modulator – Vcc = 2.5V

Photodiode High Speed PiN PD - Vcc=1.0 ÷ 1.6V

ST Silicon Photonics Platform: PIC25G 18

Back End of Layer stack cross section

Single Mode Waveguide cross-section


F.Boeuf et al., Electron Devices Meeting (IEDM),

2013 IEEE International , 9-11 Dec. 2013

300mm PhotonicsTool Set Portfolio

300mm PHOTONICS Technological Platform

300mm Process Integration 19

Etch

SiGe & Ge epitaxies

193 nm Litho

Low T° DepNi,Co,Pt silicide

193 i

Existing Tools

High volume

Sub-90nm CMOS node tools

193nm/193i photolithography

Improved Process control


Silicon Photonics pros and cons

• Key driving force

• Fabrication based on CMOS technology

High volume production

Low cost [ $/Gbps ]

Small size [ mm3/Gbps ]

• Scalability

Speed

Channel number

Wavelength number

Number of functions

Different kind of modulation

20

• Drawbacks:

• Silicon is an indirect bandgap material

Very inefficient light emitter

• Si Photodetectors not available at

1310nm and 1550nm Telecom

wavelength

• Light modulation or amplification not

possible using direct properties of Silicon


Made possible by CMOS technology

It is possible to overcome those difficulties by means of:

• Monolithic or Hybrid Integration

of different materials

• Dedicated architectures

BUT

OUTLINE 21


• Introduction





• Conclusion

Photodiode PhaseModulator SPGC PSGC DC WG

Fiber coupling 22

• Mode mismatch:

• Size 10mm vs 400nm

Spot-size converter

• Polarization problem:

• Only TE mode is propagatedin Si-waveguide

Polarization splitter AND

polarization rotator

10mm

Single-mode Fiber Optical Core

Silicon waveguide


Grating Coupler 23

Single Polarization

Grating Coupler

(SPGC)

Polarization-

Splitting Grating

Coupler (PSGC)


TE mode

Emitted

radiadion

F.Boeuf et al., Electron Devices Meeting (IEDM),

2013 IEEE International , 9-11 Dec. 2013

Carrier Depletion 24

Lightly doped p- and n- regions are realized in the

waveguide to form a p–n diode. The depletion

area of the diode becomes larger with increasing

reverse bias voltage.

PN

PNnnn

he

he

1818

8.01822

100.6105.8

105.8108.8

Real refractive index and absorption coefficient of the

doped Si regions due to the free-carrier dispersion

(R. A. Soref and B. R. Bennett - 1986):

where:

Δne is the refractive index change due to electron

concentration change

Δnh is the refractive index change due to hole

concentration change

ΔN is the electron concentration change in cm-3

ΔP is the hole concentration change in cm-3

Δe (in cm-1) is the absorption coefficient variations

due to ΔN

Δh (in cm-1) is the absorption coefficient variation

due to ΔP

losses of 0.1 dB/cm require ΔN < 2.7x1015

cm–3 or ΔP < 3.8x1015 cm–3 material


Carrier Depletion Based High-Speed Phase Modulator25

M1

M2

Single mode waveguide

np

Insertion loss vs Phase Shift vs VoltageCut-off frequency measurement


Mach-Zehnder Interferometer Modulator

0

0.5

1

0.00 0.39 0.79 1.18 1.57

Pcross

Pbar

26

LnP

LnP

gbar

gcross

0

2

0

2

sin

cos

l

l


Germanium Photodetector 27

TEM Cross Section

Top view

Ge PiN diode I-V curve(λ=1310nm) Ge PD 3dB Modulation Bandwidth


3D Integrated Silicon-Photonics Transmitter28

EIC

PIC


Travelling-wave push-pull modulator architecture

56Gbps PRBS31 MZM eye diagrams: measurements vs simulations

28Gbps PRBS31 MZM eye diagrams: measurements at quadrature point3D assembly and stand-alone EIC

Enrico Temporiti et al., ISSCC 2016

Test Interface:• DC/RF Probes• Optical head with a 16-channel Fiber

Array mounted on 6 axis micro positioner• Use of a capacitive sensor to fine adjust

distance from wafer top

300mm Photonics Testing29

Enable full auto characterization at wafer /lot scale (300mm) of:• All Optical passive devices (Waveguide /

coupler / MZI…)• Electro Optical devices: (photodiode /

modulator…)• Modulation Bandwidth up to 67GHz• BER & Eye Diagram up to 28Gbs/s

Mea

s. C

on

tro

l

Op

tica

l / R

F /

DC

Mea

s.

Fu

ll A

uto

Pro

be

r.

Test Interface

Auto alignement of the fiber array on the grating

coupler & fine positioning with piezoelectric

actuators X

Y

Optical power


OUTLINE 30


• Introduction





• Conclusion

Hybrid integration 31

• Based on Si technology, using 1 or more

Si-photonics layers on SOI

• Using 3D layers of different materials:

• III-V for laser and/or electro-absorption modulator

• SiN (or other MidEx materials) for WDM, coupling

or sensing

• Ge or SiGe for far IR applications

• Integration can rely on local epitaxy, wafer

bonding or backside processing

• Electrical connections are based on

CMOS-like BEOL

• 3D assembly using TSV and Cu-Pillar

Photonics SoC (System on Chip) able to perform several optical

and electrical functions through hybrid integration

Conclusions 32


• After 25 years of research Silicon Photonics has now reached an

industrial maturity for mass production

• Data-center market will be the main driver for the next 5 years

• Scalability, cost reduction and downsizing are key factors making

Silicon Photonics the only technology allowing to address the

requirements of future products for high speed communications

• 3D face-to-face assembly of PIC and EIC allows maximum flexibility

of both photonic and electronic processes

• Photonics on Silicon substrate has the potential to increase his

capabilities thanks to the numerous integration opportunities of

different materials

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