Advanced Thermal Management Technologies for Electronic Systems

Ken GoodsonGoodson@Stanford.EduMechanical Engineering

Stanford University MEPTEC 2005

no known solutionfin-arrays,heat pipes

excessive

volume

0

50

100

150

200

250

1999 2001 2003 2005 2007

Power Q(W)

High-Performance

Cost-Performance

(including laptops)

?

?

ITRSYear:

ITRS View of Thermal Management Challenge

heat spreaderSi chip

chip carrier

heat sink

junctionchip

qtransistors

Device-Level SEM

metal

IBM

ILDqinterconnects

Rtransistor

Ctransistor

Ttransistors

Cinterconnect Tinterconnect

Rinterconnect

Rheat sink

Cchip

Cheat sink

T

Tambient

Rchip + TIM

Tspreader

Thermal Resistance Hierarchy

Lots of Thermal Activity

Unprecedented startup climate for thermal technologies, in areasranging from microfluidics and thermoelectrics to interfaces (over $60 million in venture capital in 2004, more likely in 2005).

New technologies appearing in a conservative discipline: Pumped liquid cooling in laptops (e.g., Hitachi, Toshiba) and desktops (Apple).

Chip makers are studying liquid cooling in detail, while scaling back power density projections.

Outline

• On chip challenges & solutions• Thermal interface materials• Advanced heat sinks

1995 2000 2005 20152010

interconnectself heatingRinterconnect

On-Chip Thermal Challenges

2

d

dmm

2 Nkdd j~ ρPeak ∆T

~ 30oC at 70 nm node ~ 80oC at 50 nm node

Global WiresGlobal Wires

InterconnectTemperature

Field

Student: Sungjun Im,Proc. IEDM 2000

Silicon

Interconnect Self Heating

Temperature Contour Plot (50 nm technology node)

209 °C209 °CGlobal WiresGlobal Wires

Compounding ITRS trends lead to accelerating peak temperature:low-k dielectric materials with poor thermal conductivitiesincreasing current densities and aspect ratiosincreasing number of interconnect layers

Student: Sungjun Im. Sponsor – MARCO IFC

7.1

ILD

ILDMETMET

2 Nkdd j~ ηρPeak ∆T

0 2 4 6 8 10

120

140

160

180

200

220

Tem

pera

ture

[o C]

Distance from Substrate [µm]

35 nm

50 nm

70 nm

100 nm

130 nm

180 nm

Tem

pera

ture

Ris

e (o C

)

0

100

50

interconnectself heatingRinterconnect

microprocessorhotspots (mm scale)Rchip + TIM

On-Chip Thermal Challenges150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

0

100 W

50 W

1995 2000 2005 20152010

Rtotal(ITRS 2003)

Rchip

Rhe

atsi

nk

0

0.1

0.2

0.3 oC/W

2000 2005 2010 2015 2020

20191817161514131211109876543210

∆Tmax = 21.4 oCθj-TIM = 0.11 K/W

Conventional Heat Sink, Cu Spreader

Liquid Waterflow

Hotspot

20191817161514131211109876543210

0 5 10 15 200

5

10

15

20

125 W(125 W/cm2)

75 W (25 W/cm2)

Power Map (200W)

2 cm

2 cm

Hotspot Cooling by MicrochannelsJae-Mo Koo, Sungjun Im (Stanford)with Ravi Prasher (Intel)

Microchannel Heat Sink∆Tmax = 13.2 oC, θj-TIM = 0.066 K/W

Hotspot Cooling by Chip-integrated Thermoelectrics

Ali Shakouri, UCSC, Avram Bar-Cohen, UMD. Proc. DARPA Site-Specific Thermal Management Workshop, Jan. 2005

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 1100098

100

102

104

106

Tem

pera

ture

(o C)

Distance along the Die (oC)

Without TE Cooling (I=0A) 1-Pad Electrode, (I=0.3A) Ring Electrode, (I=0.3A)

Die Thickness=50um; q” fb = 680W/cm2 ; q”avg = 70W/cm2

Fireball = 70um; MicroCooler = 70um; Doping=1x1019cm-3

1995 2000 2005 20152010

interconnectself heatingRinterconnect

microprocessorhotspots (mm scale)Rchip + TIM

On-Chip Thermal Challenges

transistorhotspots (nm scale)Rtransistor

18 nm

ITRS transistor in 2010

Source Drain

Silicide

Bulk Silicon

GateOxide Isolation

Bulk FET

FinFET

Silicide

Silicon substrate

Gate

Strained Si, Ge, SiGe

Buried oxide

SOI/SiGe

back gate(p++ Si)

HfO2

S (Pd) D (Pd)SiO2

top gate (Al) CNT

Carbon nanotubetransistor

UC Berkeley/AMD

IBM Stanford

1995 2000 2005 20152010

Transistor Timeline

Freq

(Hz)

Energy (meV)

Phonon Wavevector qa/2π

10

20

30

40

50

60

Transistor Thermal Processes

High ElectricField

Hot Electrons(Energy E)

Source

Gate

Drain

Optical PhononsOptical Phonons

τ ~ 10 ps

τ ~ 0.1psE > 50 meV

optical(vop ~ 1000 m/s)

IBM

Heat Conductionto Package

τ ~ 1 ms – 1 s

E < 50 meV

Acoustic PhononsAcoustic Phonons

τ ~ 0.1ps

acoustic

(vac ~ 9000 m/s)

???

Students: Eric Pop, Sanjiv Sinha, Jeremey RowletteSponsors: SRC 1043, IBM, Intel

2D Monte Carlo of 18 nm Thin-Body SOI Transistor

Cur

rent

J·E

ITRS Specs:LG=18 nm, tSI=4.5 nm, tOX=1 nm NSD=1e20 cm-3, NCH=1e15 cm-3

ION=1000 µA/µm, IOFF=1 µA/µmΦGATE=4.53 eV (Mo), VDD=0.8 V

if W/L = 4 then Nelec ~ 2500 total!

Pop, Goodson, Dutton, Journal of Applied Physics, Vol. 96, p. 4998 (2004)

Phonon Hotspot TemperatureTe

mpe

ratu

re R

ise

(K)

1 Based on ITRS 2003

Targeted JunctionTemperature

Actual Junction Temperature

HotspotEffect

ULTRA-THINBODY

Year1

Outline

• On chip challenges & solutions• Thermal interface materials• Advanced heat sinks

Carbon Nanotubes in Thermal Interface Materials

• Homogeneous mixture with particlesHu, Jiang, and Goodson, ITHERM 2004, SRC patent pending

• Aligned growth (one side)Hu, Padilla, Xu, Fisher and Goodson Submitted to Semitherm 2005

• Aligned growth (two sides, “thermal nano velcro”)Work in progress! In collaboration with Dai’s group, Stanford

heat spreader

chip

Students: Xuejiao Hu, Angela McConnell, Antonio Padilla, Senthil GovindasamySponsors: SRC 1064, NSF NIRT, IBM, Raytheon, Molecular Nanosystems

heat spreader

chip

chip

heat spreader

CNT

Aligned CNTs on Silicon

Pad PadPt Line

Silicon

SiN

Pressure

Glass

Hu, Padilla, Xu, Fisher, Goodson, submitted to SEMI -THERM 2005

Attachment Pressure 100kPa (14.5 psi)

Attachment Pressure 40kPa (5.8 psi)

Stand-alone Single-walled CNT

poly Si P++

Si substrate

measure Thot

measure Tcold

AC heating current

Alnanotube

cold side

hot side

McConnell, Jiang, and Goodson, NSF Design, Service & Manufacturing Grantees and Research Conference, 2004

polysilicon

polysilicon

1 µm

nanotube

Thermal Conductances of Carbon Nanotubes

Student: Angie McConnell. Sponsor: NSF

Outline

• On chip challenges & solutions• Thermal interface materials• Advanced heat sinks

Space Wars

Heat Sinks are 3000xbigger than chip

Power Delivery~1 cm3

ASICs~1 cm3

Heat Sinks,Heat Pipes,Vapor Chambers

~ 102 cm3

~10-1 cm3

RAM~10-1 cm3

Video~10-1 cm3

They crowd away more important functional components

HOTSPOTS

“Dream Heat Sink” (1998 Brainstorm)

Fluid

ports

Microprocessor

Integrated Pump& controllermicrochannel cooling

at hotspots

Free I/OSurface

IntegratedTemperature

sensors

• no larger or heavier than microprocessor chip

• targeted cooling at hotspots

• fully-integrated, silent, reliable pump

• temperature sensors control pump flowrate

DARPA HereticIntel

1999 2000 2001 2002 2003 2004 2005

AppleAMD

Research Background

Pyrex seal

ChannelsIn silicon

Si chip

Thermalattach

Si chip

Fluidinlet

Outlet Thermalattach3D

2D

Microfluidic Cooling: Government Seed

1 cm1 cm

ElectroOsmotic PumpMicrochannel Modules

DARPA HereticIntel

1999 2000 2001 2002 2003 2004 2005

AppleAMD

CooligyStartup(VC funding)

ProductShipment

MicroCoolers for ComputersResearch Background

Micro hx

EO Pump

Heatrejector

Micro hx

EO Pump

Heatrejector

Microfluidic Cooling: Venture Growth

Zhou et al., Proc. SEMITHERM 2004, Proc. ITHERM 2004

ElectroOsmotic Pumps Groups of Santiago, Goodson, Kenny, Stanford Mechanical EngineeringSponsor: MARCO IFC, DARPA, Intel

1 cm1 cm

Vd

p 2max32εζ

=∆

µ−

−µ

εζ=

)ra(dxdpE)r(u

22

lVAQ

µεζ

=max

•Very high volume to flowrate ratio•Stanford pump performance (Feb 2003):Pmax ~ 2 atm, Qmax ~ 40 ml/min, Vol. ~ 2 cm3

EOF

+ + + +++ ++ ++ + +++ ++

Glass or fused-silica capillary wall

Charge double-layer

Deprotonated silanolgroups

+ -

Idealized pore channel:

Free-standing pump

Siliconmicromachined

pump

1999 2000 2001 2002 2003 2004 2005

MARCO

Mixed Signal I/O

Intel

mixed signal I/O module releases chip backside for RF, Photonic, MEMS I/O usingIntegrated electrical/fluidic interconnects

Microfluidic Cooling: Mixed-Signal Fluid

Mixed Signal Chip

targeted, on-demandmicrochannel cooling

Free I/OSurface

Solid-state EO pump

Mixed Signal Chip

Fluidic I/OPhotonic I/O RF

Integrated MEMSSensing

ElectricalConnections

Fluidic Cooling

Mixed Signal Chip

Fluidic I/OPhotonic I/O RF

Integrated MEMSSensing

ElectricalConnections

Fluidic Cooling

1999 2000 2001 2002 2003 2004 2005

DARPA3DIC

3D IC CoolingMicrofluidic Cooling: 3DICs

Briefly: Refrigeration Techniques

P PPN NN

Cold Side: Active Cooling

Hot Side:Heat Rejection

Current+-

Hot Side: Heat Rejection

Cold Side: Input from Chip

p n p n np

Current

Piezoelectric Actuator, ~3 kHz

Heat Exchangers

Resonator

CompressorPower

Cold Heat Exchanger:Input from Chip

Hot Heat Exchanger:Heat Rejection

Valve(Sprayor Jet)

III

Chip2. Solid State

1. Vapor-Compression

3. Acoustic

Routes to Higher PerformanceA. Majumdar, Science 303, 777 (2004)

M. Dresselhaus, Proc. EPRI Workshop, 2004

cold end

hot end

Ip nI

Point Contacts(Gmelin et al., MPI; Ghoshal et al., IBM

Low-dimensional solidswith reduced phonon conductivity

Electron Tunneling(Kenny Group, Stanford; CoolChips)

electronelectron

conductorinsulator

phonondW < λdB

e,hdW < λdBe,h dW < lmfp

phdW < lmfpph

Thermionic Transport(Bowers, UCSB; Shakouri, UCSC)

Cathode Barrier Anode

Energy

Hot electron

Cold electronHotHot ColdCold

Concluding Remarks

• Power density (W/cm2) is the critical metric for the difficulty of a cooling problem, and is as relevant for individual transistors as it is for hotspots on the microprocessor and air cooling of heat sinks and the computer case.

• Pumped liquid cooling has arrived, and will buy the industry a few more years of power density scaling, specifically to the limits of case-level heat rejection.

• Frontier research opportunities (microfluidics and microthermoelectrics) can extend power density scaling (even to 3D circuits), although they pose major challenges in chip-integration and cost.

Micro Heat Transfer LabKen Goodson, Stanford Mechanical Engineering

Current GroupSanjiv Sinha Roger FlynnXuejiao Hu Julie SteinbrennerSungjun Im (Materials Science) Evelyn Wang Kevin Ness Ankur Jain Jae-Mo Koo Fu-Min WangYue Liang Eon Soo LeeAngela McConnell Dr. Carlos HidrovoJeremy Rowlette (Electrical Engineering) Dr. Eric PopDavid Fogg Dr. Ching-Hsiang Cheng

Recent AlumniProf. Mehdi Asheghi Carnegie Mellon University (ME)Prof. Dan Fletcher UC Berkeley (Bioengineering)Prof. Bill King Georgia Tech (ME)Prof. Katsuo Kurabayashi University of Michigan (ME)Prof. Sungtaek Ju UCLA (ME)Prof. Kaustav Banerjee UC Santa Barbara (EE)Dr. Uma Srinivasan XeroxDr. Per Sverdrup Intel Dr. Peng Zhou CooligyDr. Maxat Touzelbaev AMD