lecture1: Introduction to silicon photonics - Helios project · Silicon Photonics –PhD course...
Transcript of lecture1: Introduction to silicon photonics - Helios project · Silicon Photonics –PhD course...
lecture1: Introduction to silicon photonics
Prepared by Lorenzo PavesiUniversity of Trento
Photonics
Photonics is the technology associated with signal generation, processing, transmission and detection where the signal is carried by photons (i. e. light)
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Silicon Photonics
Photonic devices produced within standard silicon factory and with standard silicon processing
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
i.e. CMOS compatible
Motivation to Silicon Photonics
Limit of microelectronic evolution where photonics can help in take pace with Moore’s lawOptical communication evolutionA new technology platform to enable low cost and high performance photonics
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Semiconductor Technology Evolution
the main thrust for semi business growth
“Smaller, Faster, Cheaper”
Moore’s lawSilicon Photonics –PhD course prepared within FP7-224312 Helios project
The invention of the transistor
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
23 -12-1947
The First Planar Transistor764 µm
SiO2N+
PN-type silicon
Al contact
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
1959
The First Planar Integrated Circuit
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
1961
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Intel 4004 Microprocessor
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
1971
Moore’s Law in microprocessors
40048008
80808085 8086
286386
486Pentium® proc
P6
0.001
0.01
0.1
1
10
100
1000
1970 1980 1990 2000 2010Year
Tran
sist
ors
(MT)
2X growth in 1.96 years!
Courtesy, IntelSilicon Photonics –PhD course prepared within FP7-224312 Helios project
Intel Pentium (IV) Microprocessor
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
2001
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Die Size Growth
40048008
80808085
8086286
386486 Pentium ® proc
P6
1
10
100
1970 1980 1990 2000 2010Year
Die
siz
e (m
m)
~7% growth per year~2X growth in 10 years
Courtesy, IntelSilicon Photonics –PhD course prepared within FP7-224312 Helios project
Die size grows by 14% to satisfy Moore’s law
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Clock FrequencyLead microprocessors frequency doubles every 2 years
P6Pentium ® proc
48638628680868085
8080800840040.1
1
10
100
1000
10000
1970 1980 1990 2000 2010Year
Freq
uenc
y (M
hz)
2X every 2 years
Courtesy, IntelSilicon Photonics –PhD course prepared within FP7-224312 Helios project
Clock Frequency
P6Pentium ® proc
48638628680868085
8080800840040.1
1
10
100
1000
10000
1970 1980 1990 2000 2010Year
Freq
uenc
y (M
hz)
2X every 2 years
Courtesy, IntelSilicon Photonics –PhD course prepared within FP7-224312 Helios project
saturation
Today chip cross section
semiconductor
interconnections
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
CPU Multi-layer Metal Increase Trend
0
1
2
3
4
5
6
7
1980-2u
1984-1.5u
1987-1.0u
1990-0.8u
1993-0.6u
1995-0.35u
1997-0.25u
1999-0.18u
2001-0.13u
# of Metal Layers
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
…here we have a problem…..
How can all these single nm long transistors talk each-other ?
The problem of interconnectsSilicon Photonics –PhD course prepared within FP7-224312 Helios project
Interconnect length
2000 2002 2004 2006 2008 2010 2012 2014 2016 20181km
10km
100km
Tota
l int
erco
nnec
t len
gth
(m/c
m2 )
year
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
10 Km long interconnect
Power dissipationLatencyDelay…..
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Wiring delay > gate delay
Delay
RC time constantsR=ρL/AC=κA/d
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Power Dissipation
Year
P6Pentium ® proc
486386
2868086
808580808008
4004
0.1
1
10
100
1971 1974 1978 1985 1992 2000
Pow
er (W
atts
)
Power delivery and dissipation will be prohibitiveSilicon Photonics –PhD course prepared within FP7-224312 Helios project
Power Density
400480088080
8085
8086
286 386486
Pentium® procP6
1
10
100
1000
10000
1970 1980 1990 2000 2010Year
Pow
er D
ensi
ty (W
/cm
2)
Hot Plate
NuclearReactor
RocketNozzle
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
The Challenges
10
100
1000
1990 1995 2000 2005 2010 2015
CPUPower(W)
SupplyVoltage
(V)
Power = Capacitance x Voltage2 x Frequencyalso
Power ~ Voltage3
Power Limitations Diminishing Voltage Scaling
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Tera-leap to Parallelism: EN
ERG
Y-EFF
ICIE
NT P
ERFO
RM
AN
CE
TIME
Instruction level parallelism
Hyper-ThreadingThe days ofsingle-core chips
Dual Core
Quad-Core
More performanceUsing less energy
10’s to 100’sof cores Era of
Tera-ScaleComputing
All this compute capability may require high speed optical links
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Chip Multiprocessors
Parameter Value Technology process 90nm SOI with low-κ dielectrics and 8 metal
layers of copper interconnect Chip area 235mm^2 Number of transistors ~234M Operating clock frequency 4Ghz Power dissipation ~100W Percentage of power dissipation due to global interconnect
30-50%
Intra-chip, inter-core communication bandwidth
1.024 Tbps, 2Gb/sec/lane (four shared buses, 128 bits data + 64 bits address each)
I/O communication bandwidth 0.819 Tbps (includes external memory)
IBM Cell:
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Interconnects pose problems
not only within the chip
Growth of the Internet
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Power due to the explosion of internet
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
To solve the interconnect problem
GO TO PHOTONICS
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Length Scales for interconnects
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Chip to Chip1 – 50 cm
Board to Board50 – 100 cm
1 to 100 m
Rack to Rack
0.1 – 80 km
Metro &Long Haul
Decreasing Distances→
Billions
Millions
Thousands
Vo
lum
es
Optical Copper
Moving to Interconnects
Drive optical to high volumes and low costs
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Optical interconnects
Source IEEE spectrum
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Evolution of optical communication
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
1958-59 Kapany creates optical fiber with cladding1960-Ted Maiman demonstrates first laser in Ruby1962-4 Groups simultaneously make first semiconductor lasers1970-First room temp. CW semiconductor laser-Hayashi & PanishApril 1977-First fiber link with live telephone traffic-
GTE Long Beach 6 Mb/sMay 1977-First Bell system 45 mb/s links 850nm MMEarly 1980s-InGaAsP 1.3 µm Lasers
- 0.5 dB/km, lower dispersion-Single modeLate 1980s-Single mode transmission at 1.55 µm -0.2 dB/km1989-Erbium doped fiber amplifier1 Q 1996- 8 Channel WDM
A few date
1970 I. HayashiSemiconductor Laser
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Brief story of optical communication
Evolution of optical data link
Optical fiber system has the capacity to hold the whole internet traffic
It doubles each 9 month vs moore’s law 18 months
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
In 2000, for the first time, semiconductor revenues in communication exceeded revenues in PC sector.
Source: Kimerling
Technology in the Internet Age
15%
20%
25%
30%
35%
1996 1997 1998 1999 2000 2001
PC
Communications
% o
f Sem
icon
duct
or E
lect
roni
cs R
even
ue
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
The next challenge
No opticshere
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Major limit of photonics
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Complexity in today PIC
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Innovation driven by cost
Material comparison
λ (μm)
Band gap
Δn/n (%) Tx Rx waveguides Optical component
Si 1.1 I 70 No Yes Yes Yes
GaAs 0.8 D 0-14 Yes Yes Yes Yes
InP/InGaAs 1.55 D 0-3 Yes Yes Yes Yes
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Big challenges
How to merge photonics and electronicsHow to move optical communication to the chipHow to standardize photonicsHow to
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Big challenges
How to merge photonics and electronicsHow to move optical communication to the chipHow to standardize photonicsHow to
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Silicon photonics solution to these challenges?
Why do we want to use silicon
Because silicon is an optical material
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
General properties at room T
50Silicon Photonics –PhD course prepared within FP7-224312 Helios project
http://ww
w.icknowledge.com
/misc_technology/S
ilicon%20properties.pdf
Silicon is an Excellent Optical Material
High refractive index difference with SiO2nSi=3.5
nSiO2=1.45
1 3 5 7 9 11 13Wavelength (um)
1 3 5 7 9 11 13
Wavelength (μm)
0
4
8
12
Abs
orpt
ion
(dB
/cm
) TransparentWindow
1.2 – 6.5 μm
Source: UCLA
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Silicon is easily shaped
• ultra-compact waveguides• features: 50-500 nm ± 1-10 nm• fabrication in CMOS fab(deep UV lithography)
Record low lossachieved
Photonic crystal waveguide Photonic wire waveguide
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
• IC’s are made of Silicon (>98%) even for high frequency applications(cellular phone)
Why silicon
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Silicon is cheaper than other semiconductors
* Source waferworld.com**Assumed equal processing cost (1000 €), die size 1 cm, yield =1
P4 2.6GHz 200$
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Wafer size (R&D)
Wafer size (commercial)
Wafer cost(€)
mm² substrate cost(€)
Si 450 mm 300 mm 100 0.001
SOI ? 300 mm 800 0.008
InP 150 mm 100 mm 300 0.03
GaAs 200 mm 150 mm 300 0.013
Mature and widespread technology
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Band diagram
SiliconGallium Arsenide
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
Silicon limit
Indirect band gap = low radiative recombination probability = long
radiative lifetimes (ms)
Free carriers move around =Non-radiative recombinations prevail
Extremely low internal quantum efficiency in bulk silicon (10-6)
Silicon Photonics –PhD course prepared within FP7-224312 Helios project
60Silicon Photonics –PhD course prepared within FP7-224312 Helios project
acknowledgements
All those who have posted beautiful images and slides on the internet which I have re-used here
62Silicon Photonics –PhD course prepared within FP7-224312 Helios project