the value and supply chain impact of wide bandgap substrate · pdf file ·...

Dr. Hans Stork

Senior VP and CTO

ON Semiconductor

July 13, 2016

The Value and Supply Chain Impact of Wide

Bandgap Substrate Materials

2 07/13/2016 Semicon West

Outline

• Wide Bandgap Materials Properties

• The Application Challenge

• Wafers, Module Substrates, Reliability…

• Conclusions


AlGaN/GaN HEMT Opportunity for a revolution?

Noise Figure (NF) - Less Carrier Scattering

- Small RF Loss

Maximum Oscillation

Frequency (fmax) - High Saturation Velocity

- Small Parasitic Capacitance

Maximum Drain

Current (Imax) - High Carrier Density

- High Electron Mobility

Maximum Breakdown

Field (BVDmax) - High Carrier Density

- High Electron Mobility

Maximum Operating

Temperature (Tjmax) - Wide Bandgap

- High Potential Barrier

(A/mm) (dB)

(V/um)

(Deg C)

(GHz)

400

300

200

100

0


WBG FOM Comparison


Materials Comparison Metric Si GaAs SiC 4H GaN Diamond Comments

Band Gap, Eg (eV) 1.1 1.4 3.3 3.4 5.4

Reference: GaN-Based RF Power Devices and Amplifiers; Proceedings of the IEEE | Vol. 96, No. 2,

February 2008, Table 1

Dielectric Constant, εr 11.8 13.1 10 9 5.5

Critical Field, Ebr (MV/cm) 0.3 0.4 3 3.3 5.6

Electron Mobility, µn (cm2/V-sec) 1350 8500 700

1200 (Bulk) 2000

(2DEG) 1900

Electron Saturation Velocity (106cm/sec) 10 10 20 25 27

Thermal Conductivity (W/cm K) 1.5 0.43 3.3 - 4.5 1.3 20

Johnson's FoM: Ebr*vsat/2π 1 2.7 20 27.5 50

Power Capability 3 1 2 GaN has the largest band gap and critical field. Thermal conductivity is comparable to Si.

Frequency Capability 3 2 1

GaN is better than SiC and Si (but, worse than GaAs and InP). GaN can deliver high power and high frequency simultaneously. The heterostructure can be another advantage of GaN (2DEG: high electron mobility due to no impurity scattering.)

Rdson (Power Application) 2 1 1 Rdson is made up of contact and channel resistances. Better ohmic contact can be made to Si due to smaller band gap. For high voltage, channel resistance dominates Rdson. High carrier concentration and short distance enable lower Rdson in GaN and SiC than in Si. For RF application, contact resistance is as significant: similar Rdson between Si, GaN and SiC.

Rdson (RF Application) 1 1 1

Temperature Impact on Rdson 3 1 2 For SiC Rdson only increases about 20% when temperature increase from 25° to 135° C, while Rdson of Si increases ~2x. GaN is in between .

Range of Devices 1 2 3

SiC is equivalent to Si with a higher breakdown field and thermal conductivity. SiC MOSFETs, diodes and trench devices are possible. Difficult to make vertical GaN. Also difficult to make P type GaN i.e CMOS-GaN.

Driver Integration 1 2 3 Enhancement devices are possible on SiC. Co-packaging required to incorporate D-mode GaN into standard driver application. Early enhancement mode devices have been demonstrated with GaN HEMT.


Basics in All Power Devices

b [

µm

]

b [

µm

]

b [

µm

]

b [µm]

Si

Buffer

GaN f [nm]

AlGaN

Material Properties Device structure

GaN HEMT SiC xFET Si MOSFET Si IGBT

+ Diode (Si or SiC)

• Current flows vertical in Si & SiC based power devices Ploss_on ≈ f(1/A; b)

• GaN performance is based on 2DEG in a horizontal interface Ploss_on ≈ f(1/l; b)

• Voltage capability in the current path is defined by distance b BVCES ≈ f(b)

• Switching losses are influenced by charges in the volume Ploss_switch ≈ f(A; b)

• Ability to dissipate losses is proportional to die size Pdissipate ≈ 1/Rth ≈ f(A)

In all technologies die size is affecting losses and dissipation ability


Consumer Application

• Early adoption of WBG rectifiers & transistors requires systems solutions

Mini Adapter Proof of Value • Reduce 65/85 W adapter to a fraction

of the volume.

• Utilize GaN/SiC transistors

Significantly raise switching freq.

Hold efficiency to very high level.


Electrical Vehicle Systems

• Introduce GaN in future generations of Electrical Vehicles (SOP 2017)

Lower power losses (5% increased efficiency) and reduce the weight of Power

Systems (30% cost savings).

Eliminate the need for liquid cooled systems, the DC-AC inverter, the charger,

and the DC-DC inverter (up to 17% cost savings).

DC-AC inverter

3 phases, 60kW

DC-DC converter

Battery charger Battery Management

Motor

(Source: Renault)

(Source: Infineon)

Half bridge of a DC-AC inverter:

4 x (Infineon IGBT’s+ diodes)

Increased Efficiency Inverters for Automotive Without Liquid Cooling.


Possible SiC Power Applications

Yole 2014


Technical consequences

Consequences particular relevant for individual applications

SiC and GaN Only GaN

Physical properties Consequences

Lower switching losses

Lower RDSon

Smaller area of chip

Integration possible

System volume & weight

High Electron mobility

Large band gap and breakdown field strength

Lateral concept

Dis

crete

Syste

m

Sm

alle

r num

ber

of h

eat s

inks

Higher efficiency

Higher1 frequency

Passiv

es w

/ re

duced

volu

me &

weig

ht

WBG Differences and Consequences


Internal GaN Development at ON Semi MOCVD • Since April 2014

6” Device fab • Since Q2 2013

Device

characterization • 650V DHEMT

• Current rating till 50A

• Yield >85%

• Temp char up to 200oC

• Early reliability done

0.1

1

10

100

1000

0

5

10

15

20

25

30

35

40

0 100 200 300 400 500 600 700 800

Ids

off-s

tate

(nA

), Igs

off-s

tate

(nA

)

I ds

on

-sta

te (

A)

Vds (V)

Ids<100nA

Igs<2nA

Grd substrate Lgd=15µmW=364mmRon~40mΩ

40A at Vds=1.6V

Assembly and

application • 650V cascoded switch &

rectifier Dec 2013

• Testing several topologies

• Bi-directional switches

• Half-Bridge (below)


6 versus 8 inch for GaN-on-Si

Motivation of GaN on Si: Leverage 8” Fab infrastructure

Case Study: Finished Goods cost for 70mOhm/650V device

Assumptions:

• Fab process cost 8 inch = 1.25x 6 inch

• #die 8” = 1.78 #die 6”

• MOCVD wafer yields taken independent of wafer size – optimistic, 8 inch probably lower in near term

• Probe yields taken independent of wafer size – optimistic, 8 inch probably lower in near term

• No additional capex for 8” line

Conclusion: incremental (15-20%) cost benefits for 8” only materialize at high reactor (>80%) utilization, ie wafer volumes not yet seen


• First reported growth of SiC crystals dates back to 1892

• Production of semiconductor grade SiC ingots is one of the most challenging tasks faced by the SiC semiconductor and industry.

• A major breakthrough came around 1980 with the introduction of SiC seed crystal sublimation growth using a high quality seed crystal surface to begin growth process.

• The seeded sublimation growth is often referred to as the physical vapor transport method (PVT).

SiC Substrate Developments


Schematic representation of the standard PVT reactor

SiC Substrate Equipment


Comparison of Cascode QFN Designs 8x8 QFN Source Down 8x8 QFN Drain Down

Next Gen 8x8 QFN Source Down


Thermal heating : Tjunction

• For lifetime predictions, Tjunction is important

• Tjunction=Tambient+T

• Due to high power density in GaN, T can be substantial – Dependent on die size and power dissipation

• Experimental validation by µ-Raman, DC conditions [Power,

TED 2015]

• Tjunction under application testing (Infrared spectroscopy)

0 10 20 30 40 5020

40

60

80

100

120

140

160

180

200

220 0.3 W/mm

0.2 W/mm

0.1 W/mm

Te

mp

era

ture

(°C

)

Total channel width (mm)

30

35

40

45

50

55

60

65

70

90

91

92

93

94

95

96

0 50 100 150 200 250 300

Tju

nc

(oC

)

Eff

icie

nc

y (

%)

Pin (W)

750 kHz CCM PFC


Substrate Developments: Thermal vs electrical

L/F

IMS

DBC

eDPC

Embedded

ZrO2

ZrO2

AlN

AlN Si3N4

Si3N4

MIS Laminate

SOP40 PQFN SIP6(Igniter)

• Cu plating technology

• Two different Cu thickness for power

and signal separately

• Different ceramic materials

• Cu sintering and etching technology

• High power application

• Different ceramic materials

• Cu lamination and etching technology

• Low & middle power application

• Continued high Tg(>175ºC) insulation

material development

• Embedded technology

• Eliminate either W/B or clip

interconnection

• Mold and BT materials are evaluated

Lθ ＴＬＨＬθ BN

• Aim at low power white goods market

• Various L/F-base platforms developed

• Thicker L/F is preferred for thermal spread


– Interfaces

• HEMT is buried channel device at AlGaN/GaN interface

• MISHEMT needs TDDB characterization

–Ohmic contact reliability

• Power density can be 10x higher than in Si

• Degradation limited to 10% but not completely understood

–HTRB

• Parametric shifts occur during high voltage, high temperature stress

• Improvements seen with buffer and interface engineering

– Drain Accelerated stressing

• Statistical models needed, requiring volumes of data

Reliability Issues in GaN


Industry / technology activity Consequence / reaction

Market expectations for wide-bandgap

materials at all time high

• Opportunity with high technology and

application risk

Application specific trade-offs divide market

opportunity for increasing frequency

• SiC FETs: costly but effective >1200V

• GaN on Si: speed potential requiring new

topologies, adding uncertainty

Cost and performance of substrate much

more significant compared to Si

• Vertical integration of substrate and device,

development and manufacturing

Packaging also significant in extracting

maximum performance and optimize cost

• Cascode configuration is min-module

• Adding complexity in supply chain

Most applications expect parity with Silicon

in use, cost, and reliability

• High volume, price tolerant application

needed to drive production learning

• Optimize total supply chain

Thank you • Q&A

Summary of Observations

1

2

3

4

5

6


Q&A

Q&A


Abstract

Wide bandgap materials have received much attention for their potential to revolutionize the

world of power devices. Spider chart comparisons of the materials properties of GaN or SiC

show just about every property outperforming their Silicon counterpart. Higher breakdown,

higher mobility, higher temperature tolerance allowing lower resistance, lower capacitance,

higher frequency devices. Market forecasts counting on fast growing adoption in new markets

such as renewable energy and electrical vehicles are reaching into the billions of dollars, and

are just around the corner…

The realization of these promises is more complex due to the need to redesign not only the

transistors themselves, but also the packaging, the circuit topology, the system architecture,

and the application. And with more of the cost and the features determined by the substrate

itself, several elements of the supply chain from substrate growth, to epitaxy, to dicing and

assembly need adjustments from the established Silicon world as well.

In this brief overview, key features and challenges for GaN-on-Si will be discussed and

highlighted with experimental results at ON Semiconductor.

the value and supply chain impact of wide bandgap substrate · pdf file ·...

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