Leti Versatile Silicon Photonics Platform

DATE 2020| Quentin WILMART | 2020-03-13

LETI VERSATILE SILICON PHOTONICS PLATFORM

Contribution from all members of Silicon Photonics Lab @ LETI

| 2

Silicon photonics laboratory of CEA-LETI: presentation & scope of applications

Building block focus:

- Ultra-low loss silicon waveguides

- 3D photonics : Si-SiN platform

- Active devices: modulator & photodiode

- Hybrid III-V/Si laser

Fabrication platform & device library

OUTLINE

DATE 2020| Quentin Wilmart | 13 Mars 2020

Towards a 300mm platform

Conclusion

| 3

SILICON PHOTONICS LAB:

Silicon photonics :

High integration level, scalability, low-cost mass production in CMOS fab

Silicon photonics lab at CEA-LETI:

Core team : 30 collaborators

Conference board members at OIC, GFP, ECTC, ESTC

Patent portfolio > 70

Process integration

Fabrication platform:

200 & 300mm

Device and circuit

design

Device library

Testing

Automatic prober

200 & 300mm

Circuit and modules

Packaging


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Silicon Photonic Links

Transmitter

Receiver

HIGH-SPEED OPTICAL COMMUNICATIONS

Data transmission: historical application of silicon photonics

• Solving electrical interconnect limits in Data centers, Supercomputers and

ICs with higher capacity, lower cost optical interconnects

• Exponential growth of data traffic

• Product: Intel 100G transceiver. 400G & 800G expected. Google Data center

3D

integration

High data rate modulation

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3D SENSING: LIDAR

Solid state beam steering: optical phase array for Lidar

• 1st demonstration with SiN waveguides (large transparency windows)

• Several projects in progress


phase tuning

sections Power splitter array

Laser inputEmitter array

N. A. Tyler et al. Optics Express, Feb. 2019.

Tyler, N. A., et al. CPMT Symposium BEST

PAPER AWARD

Q. Wilmart et al. , Applied Sciences 2019

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NEUROMORPHIC COMPUTING

Artificial intelligence with photonic circuits

• Linear operation (matrix multiplication) with Mach Zehnder arrays

• Non-volatile phase shifter (new material under investigation)

• Non-linear operation


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QUANTUM COMPUTING & COMMUNICATION

Quantum optics with silicon photonics technologies

• Entangled photon pair generation with Si3N4 or Si ring by non-linear effect

→ ultra low loss waveguide required (3dB/m in Si3N4 demonstrated)

• On-chip single photon detection: superconducting NbN on Si

• Complex circuit for manipulation (+ filters)


Superconducting single photon

detector in 200mm platform

Demonstration of photon entanglement. Made @ Leti

El Dirani et al, Opt. Exp. 2019,

Sabattoli et al. ICTON 2019NON LINEAR GENERATION OF

QUBITSMANIPULATION OF QUBITS

DETECTION OF

QUBITS

NbN based

superconduct

ing material

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OUTLINE



Conclusion

| 9DATE 2020| Quentin Wilmart | 13 Mars 2020

TECHNOLOGY KEY PROCESS FEATURES

• Si photonics platform

Substrates : SOI 310nm

> 200 steps

24 litho levels

40 metro/control steps

Flexibility: possibility to integrate the SiNlayer for thermal properties or III-V epitaxies for hybrid lasers

• Process building blocks

Multilevel silicon patterning PN Silicon junctions Germaniun SiN waveguides Integrated resistance (heater) Integrated laser (direct bonding of III-V wafers/dies) Planarized BEOL : 2 AlCu routing levels

AWG MUX

1D GC

MMIGe photodiodes

MZ modulator ring modulator

2D GC

Rib WG

Device library

III/V

III-V/Si hybrid laser

SiN

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OUTLINE



Conclusion


ULTRA-LOW PROPAGATION LOSS SILICON WAVEGUIDES

• Sidewall roughness is the main cause of propagation lossesin Si waveguides

Roughness reduction with smoothing annealing (H2 850°C)

Edge roughness < 1nm

No shape modification: no impact on other devices

No impact on modulator efficiency

Huge improvement of propagation losses: new state-of-the-art

Strip

200nm200nm

Non-annealed annealed

Prop. losses wafer map

@1550nm (in dB/cm)

Grating coupler

(with or without annealing):

λcenter = 1310nm

I.L. = 2dB ; BW(-1dB) = 30nm

Collaboration

with CNRS-LTM

as part of IRT

Q. Wilmart

et al., GFP

2019

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ADD-ON: SILICON-NITRIDE AS A PHOTONIC LAYER

SiN

Si

Why Silicon nitride:

• Low refractive index (nSiN = 1.88)

→ less sensitive to fabrication imperfections

Waveguide: 0.6dB/cm

• Low thermo-optic coefficient ( ~2x10-5 K-1)

→ Temperature quasi-insensitive multiplexer

• Broadband coupling scheme

600nm

200nm

300nm

2D-F

DTD

inse

rtio

n lo

ss(d

B)

Mea

sure

din

sert

ion

loss

(dB

)

Wavelength (nm) Wavelength (nm)

(a) (b)

80nm CWDM 80nm CWDM

(d)(c)(c)

SiN/Si SP

GC M

in. IL (d

B)

SiN/Si SP

GC M

ax. cWD

MIL (d

B)

• Broadband SiN/Si grating

couplers: BW(-1dB) = 50nm

SiN only

Si

Si-SiN

• SiN edge coupler

I.L. <2.4dB over O-band

Photonic

chip

fiber

• SiN CWDM multiplexer

I.L. < 2.5dB

Xtalk < -30dB

Thermal shift: 13pm/°C

Q. Wilmart et al. ,

Applied Sciences

2019

Q. Wilmart et al.,

Photonics West

2020

Cross section


ACTIVE DEVICES: P-N MODULATOR

Szelag et al., ”Optimization of a 64Gbps O-band Thin-Rib PN Junction Mach-Zehnder” SSDM, 2018

Parameters Thin-rib

VpiLpi@-2V (V.cm) 1,5

Losses (dB/mm) 0,7

BW@-6dB (GHz) 25

Electro-optical characteristics Modulation characteristics

Mach-Zehnder modulator

32GBaud PAM4Bias PN : +4V

PDFA_IN = -10dBm

PDFA_OUT = 0dBm


ACTIVE DEVICES: PHOTODIODE

Width 0.8µm

Length 15µm

Responsivity 0.7 A/W

Dark current @ -2V

5 nA

BW @ -2V > 35GHz

Eye diagram at

64Gbps NRZ:

BER=𝟑 ∗ 𝟏𝟎−𝟓

(SNR=4)

High speed Si-Ge-Si photodiode

H. Zegmout et al., Photonics West 2020

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III-V INTEGRATION ON SI-PHOTONIC CHIP

200mm Si wafer with III-V

die bonding

III-V heterogeneous integration:

• Hybrid lasers with cavity or filtering in Si

(DBR, DFB, FB, tunable laser)

• Electro-absorption modulator

• Semiconductor optical amplifier

200mm CMOS compatible process

Die bonding for multiple epitaxies

III-V patterning

2-level BEOL – Ohmic contact on III-V

III-V Si

• Ith=60 mA

• Output power : 0.4

mW (3 mW coupled to

the WG)

• Rs=10Ω

IIIV

Si

DFB laser

K. Hassan et al., SSDM 2018

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OUTLINE



Conclusion

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300MM SILICON PHOTONICS PLATFORM

Advantage of 300mm

• Better process uniformity and control (deposition thickness,

etching depth, planarization)

• Improving components performance and stability

• Patterning: immersion lithography with enhanced resolution

Minimum dimension : 60nm (trench or line)

• Optical Proximity Correction

Si-SiN 3D photonics

BEOL in progress

Improving grating coupler with metamaterials

Non intuitive devices

Insert

ion loss (

dB

)

λ (nm)

C. Dupré et al., Photonics West 2020

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CONCLUSION: SILICON PHOTONICS IN LETI


Versatile silicon

photonics platform -

200mm & 300mm

Component library: passive

& active (up to 64Gbps)

Low loss Si waveguide with

smoothing annealing:

1dB/cm for strip &

<0.2dB/cm for rib WG

Si3N4 waveguides @ 3dB/m

for non-linear optics &

quantum photonics

Si-SiN platform (3D

photonics) temperature

insensitive CWDM

multiplexer and

broadband coupler

OPA for on-chip Lidar

III-V on Si

technology for

integrated lasers

(200mm, CMOS

compatible)

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ACKOWLEDGMENT


Silicon photonics lab: process integration, design and test teams

Laetitia Adelmini, Laurence Baud, Stéphane Bernabé, Stéphane Brision, Olivier Castany, Benoit

Charbonnier, Yohan Desieres, Cécilia Dupré, Jonathan Faugier, Daivid Fowler, Stéphanie Garcia, Fabien

Gays, Philippe Grosse, Sylvain Guerber, Karim Hassan, Christophe Kopp, Stéphane Malhouitre, Viviane

Muffato, André Myko, Ségolène Olivier, Thierry Pellerin, Wilfried Rabaud, Bertrand Szelag, Valentin

Ramirez, Corrado Sciancalepore, Léopold Virot, Quentin Wilmart, Hanae Zegmout.

PhD students: Houssein El Dirani, Cyril Barrera, Ismael Charlet, Josserand Gaudy, Marouan Kouissi,

Thomad Mang, Federico Sabattoli, Raouia Rhazi

Clean room staff

Leti, technology research institute

Commissariat à l’énergie atomique et aux énergies alternatives

Minatec Campus | 17 rue des Martyrs | 38054 Grenoble Cedex | France

www.leti-cea.com

Thank you

« Part of this work was funded thanks to the French national program

“Programme d’Investissements d’Avenir, IRT Nanoelec” ANR-10-AIRT-05

Leti Versatile Silicon Photonics Platform

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