comm dhodgecsics11presentation

7/31/2019 Comm DHodgeCSICS11Presentation

1/18

A Robust AlGaN/GaN HEMTTechnology for RF SwitchingApplications

Michael D. Hodge1,2, Rama Vetury1, Jeff Shealy1,and Ryan Adams2

1) RF Micro Devices, Charlotte, NC

2) University of North Carolina at Charlotte, Charlotte, NC


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Outline

Advantages of GaN Materials for RF Switching

Background on GaN reliability

OFF-State Step Stress Experiment

Conclusion


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GaN Material Advantages

Ruggedness

Low Loss,Low Noise

PowerHandling

UNREALIZEDPotential


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Why GaN for RF Switches ?

GaN-on-SiC

Engineer COFF, low Ron high BKDN

high ID,max

Low RTH

High Max TCH

Si PSi PSi PSi P----iiii----N:N:N:N:

Drive CurrentDependence

GaAs pHEMT:GaAs pHEMT:GaAs pHEMT:GaAs pHEMT:

BKDN vs RON Trade

Si P-i-N GaAs FET GaN FET

Loss

Isolation

Power Handling

Speed

Linearity

Operating Efficiency Engineering Complexity

High Power RF Switch Technologies


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Device Design - GaN RF switch

Path Control FET

Symmetric Operation

Power Amp/Switching FET

Non-symmetric Operation

Gate

Source Connected FP

DrainSource

PA FET

SiN

Gate

S/DS/D

LGCFP

Switch FET

LG-O

LG

SiN

Switch

LNA

HPA


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GaN High Temperature Reliability Test

18 19 20 21 22 23 24 25 26 27 2810

0

102

104

106

108

1010

1/kT

MTT

F

350 325 300 275 250 225 200 175 150

Tch (C)

18 19 20 21 22 23 24 25 26 27 2810

0

102

104

106

108

1010

1/kT

MTTF

350 325 300 275 250 225 200 175 150

Tch (C)

RFMDGaN1High Power

RFMDGaN2High Linearity

GaN High TemperatureReliability Test

SampleSize

GaN1High

Power

GaN 2High

Linearity

TotalDevices

Wafers

Fab Lots

Epi Vendors

Number ofTemperatures

Results GaN1HighPower

GaN2High

Linearity

MTTF Hrs

Ea eV

TCHANNEL C

VDS V


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Reliability Concerns in GaN HEMTs

Inverse Piezoelectric Effect (IPE)

Requires

High electric field

Observed to have no time

dependence

Impact

Physical crystal defect

Symptoms

Parametric degradation

Ron, Idmax, Idss

Increased gate leakage

Hot Electron InducedDegradation (HEI)

Requires

High electric field

Carriers

Time dependent

Impact

Hot electrons induce traps in bufferand/or barrier layers

Symptoms Parametric degradation

Ron, Idmax, Idss

7


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Inverse Piezoelectric Related Literature

Failure Within Minutesof Stress

20-100 minutes

2T is the most stressful

Critical Voltage

17-38V (GaN-on-SiC)

Study Stress Conditions Critical Voltage (V) Total Stress Time (Mins) Technology Notes

(1) Joh 2006 Vds=0V, Vgs=-15V to -34V 17-34V 100 GaN-on-SiC Lg dependent

(2) Joh 2008 Vds=0V, Vg=-10V to -50V

Vgs=-8V, Vd=10V to 50V

27V (2T)38V (3T)

40 GaN-on-SiC 2T stress harsher than3T

(3) Demirtas2009

Vds=0V, Vgs=-1V to 20V 37V GaN-on-SiC70V GaN-on-Si

20 GaN-on-SiCGaN-on-Si

Vcrit of GaN-on-Si >GaN-on-SiC

(4) Makaram2010

Vg=-7V, Vd=8V to 50V 150C base

Vg=-7V, Vd=50V 150C base

20V 42

10 and 1000

GaN-on-SiC Metal etch to reveal pits


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-200

-150

-100

-50

0

50

100

150

200

-200

-150

-100

-50

0

50

100

150

200

0 10 20 30 40 50 60

Vgs(V)

Vds=

0V

Vds(V)

Vgs=

-8V

Time (mins)

Device A - Condition 1&3

Device B - Condition 1&3

Device A - Condition 2&4

Device B - Condition 2&4

Base TempConditions 1&2 = 25C

Conditions 3&4 = 85C

Step Stress Test Conditions

Designed to replicate IPE literature stress test conditions2

Lds = 4.25um

2 .J. Joh and J. A. del Alamo, Critical Voltage for Electrical Degradation of GaN High-ElectronMobility Transistors, IEEE Electron Device Lett., vol. 29, no. 4, pp. 287-289, Apr. 2008.

Device A Lds = 3.1um

Vbd = 110V

Device B

Lds = 4.5um Vbd = 200V


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-25

-20

-15

-10

-5

0

5

0 10 20 30 40 50 60 70 80 90 100

Ron(%)

Stress Voltage (V)

Device A - Condition 1

A1

A2

A3

A4

A5

Tbase= 25C, Vds= 0V, Vgs= 0 to -100V

-25

-20

-15

-10

-5

0

5

0 10 20 30 40 50 60 70 80 90 100

Ron(%)

Stress Voltage (V)


A1

A2

A3

A4

A5

Tbase= 25C, Vds= 0 to 100V, Vgs= -8V

-25

-20

-15

-10

-5

0

5

0 10 20 30 40 50 60 70 80 90 100

Ron(%)

Stress Voltage (V)


A1

A2

Tbase= 85C, Vds= 0V, Vgs= 0 to -100V

-25

-20

-15

-10

-5

0

5

0 10 20 30 40 50 60 70 80 90 100

Ron(%)

Stress Voltage (V)


A1

A2

Tbase= 85C, Vds= 0 to 100V, Vgs= -8V

No degradation of Ron up device breakdown

No degradation in Idss and Idmax observed

Any degradation is


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No degradation of Id

Negative threshold shift

Indicates enhancement of channel carriers

Step Stress Test Results Device A


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Longer term stress

Held at most stressful condition according to literature

Vds=0V, Vgs= -100V

No further parametric change after 6 and 60 hours.

Step Stress Test Results Device A


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Summary of Step Stress

Comprehensive OFF-state stress test

Multiple bias configurations

2 Terminal 3 Terminal

Multiple base temperatures

25C

85C

Devices stressed just before catastrophic breakdown

No parametric degradation observed

Ron

Idss

Idmax


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Conclusions

No degradation observed in the OFF-state stress

No IPE related degradation observed in AlGaN/GaN switch FETs

AlGaN/GaN technology robust for RF switching applications


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Acknowledgements

The authors would like to thank for their support and discussions

AFRL

Dr. John Blevins

Dr. Chris Bozada

ONR

Dr. Paul Maki


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Appendix


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RFMD GaN Power Amplifier

No difference over extended time

300 hours and 1016 hours overlays

Stress Study Results PA OFF-State

Test Condition Base Temp (C) Vds (V) Approx Id(mA/mm)

Pdiss (W/mm) Vgs (V)

1 245 60 0.03 0.0018 -10

2 245 100 2 0.2 -10

No crystal defect


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Constant Stress Test Result

OFF-State No degradation observed

Results are inconsistent with IPE related degradation

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