SiGe Semiconductor Devices for

Cryogenic Power Electronics – III

IMAPS Advanced Technology Workshop on Reliability of Advanced

Electronic Packages and Devices in Extreme Cold Environments

Pasadena, 21-23 February 2005

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Outline

> The Team and Coordination

• Goals & Applications

• Technical Objectives & Approach

• SiGe Cryo Power HBTs

• SiGe Cryo Power Converters

• Summary & Plans

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R. R. Ward, W. J. Dawson, L. Zhu, R. K. Kirschman

GPD Optoelectronics Corp., Salem, New Hampshire

G. Niu, R. M. Nelms

Auburn University, Dept. of Electrical and Computer

Engineering, Auburn, Alabama

O. Mueller, M. J. Hennessy, E. K. Mueller

MTECH Labs./LTE, Ballston Lake, New York

R. L. Patterson, J. E. DickmanNASA Glenn Research Center, Cleveland, Ohio

A. HammoudQSS Group Inc., Cleveland, Ohio

The Team

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NASA SBIR Phase I and II

DARPA STTR Phase I

Coordination

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Outline

• The Team and Coordination

> Goals & Applications

• Technical Objectives & Approach

• SiGe Cryo Power HBTs

• SiGe Cryo Power Converters

• Summary & Plans

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Overall Goal

• Semiconductor devices (diodes and transistors)

• For power management and distribution (PMAD)

– Electrical power storage and transmission

– Power conversion for motors/generators

• For superconducting or cryogenic systems

• Temperatures down to ~20 K

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NASA Interest

• Cryogenic systems for spacecraft/aerospace

• Cold Solar System sites

• Fly-by, orbiting, landers, rovers, penetrators, ...

• Propulsion systems

• Power generation/storage/distribution systems

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Solar System Temperatures

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Temperatures for Spacecraft

TemperatureBody or location

(°C) (K)

Phobos (satellite of Mars)a –112 160

Moona –150 120

Eros (near-Earth asteroid)a –150 120

Jupiter orbitb –150 120

Europa (satellite of Jupiter) –160 110

Saturn orbitb –180 90

Titan (satellite of Saturn) –180 90

Uranus orbitb –210 60

Neptune orbitb –220 50

Pluto orbitb –230 44

Triton (satellite of Neptune) –235 38

Interstellar spaceb <–233 <40

a“Nighttime” temperature. bBlack-body equilibrium temperature.

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Specific NASA Technical Goals

• Demonstrate SiGe devices at cryogenic temperatures,

down to ~20 K

• Device types: SiGe HBTs, MOSFETs, IGBTs

• Demonstrate SiGe superiority over Si devices for

cryogenic power circuits

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Separate STTR Program from DARPA

Phase I, June - December 2004 with Auburn University

Coordination

NASA SBIR HBTs, MOSFETs,(IGBTs)

20 K “Medium” power,~100 W*

DARPA STTR Diodes, thyristors,circuits

55 K “High” power,100 W (Phase I)*1000 W (Phase II)*

*Converted power capability.

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Coordination – Goals

Device/circuit Project I (A) V (V) P (W) f (MHz) T (K) Notes

HBT NASA SBIR Ph II 2 100 - - - 0.1 to 20

MOSFET NASA SBIR Ph II 2 (5) 40 (100) - - - 0.1 (1) to 20 [1]

IGBT (if possible) NASA SBIR Ph II 2 (5) 100 (200) - - - 0.1 (0.5) to 20 [1]

Diode DARPA STTR Ph I 10 300 - - - - - - to 55 [2]

Thyristor simulate DARPA STTR Ph I - - - - - - - - - - - - to 55 [3]

Thyristor DARPA STTR Ph II 5 >300 - - - - - - to 55 [3]

Power converter DARPA STTR Ph I - - - - - - >/=100 - - - to 55 [4]

Power converter DARPA STTR Ph II - - - - - - >/=1000 - - - to 55 [4]

Power converter DARPA STTR Ph II - - - - - - >/=1000 - - - to 55 [5]

[1] Numbers in parentheses for I, V, f are additional goals beyond the minimum.

[2] Forward voltage, switching speed, and loss superior to that of equivalent Si power diodes.

[3] On-state voltage, switching speed, and loss superior to that of equivalent Si thyristors.

[4] Using SiGe diodes.

[5] Using SiGe thyristors.

grayNASA in bold, DARPA Phase II in

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Outline

• The Team and Coordination

• Goals & Applications

> Technical Approach

• SiGe Cryo Power HBTs

• SiGe Cryo Power Converters

• Summary & Plans

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Why SiGe?• Incorporate desirable characteristics of Si and Ge

• Can optimize devices for cryogenic applications by selective use of Ge, Si and SiGe

• SiGe provides additional flexibility through band-gap engineering (% of Ge)

• Devices can operate at all cryogenic temperatures (as low as ~ 1 K if required)

• All device types work at cryogenic temperatures–

Diodes

– Field-effect transistors– Bipolar transistors

• Compatible with standard semiconductor processing

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Materials Comparison

Parameter Want Si Ge SiGe

P-N junction forward V Low High Low Medium

Reverse breakdown V High High Low High

Mobility at cryo temps High Med High High

Switching speed High Adequate Adequate High

Operating temp range RT to ~20 K RT to ~100 K(due to BJT)

RT to < 20 K RT to < 20 K

Gate dielectric for MOS High quality,easily produced

Yes Difficult Yes

Compatibility withexisting processing

High High Low High

Bold = Exhibits desirable characteristic, Italic = Predicted

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P-N Junction (Diode) Forward Voltage

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SiGe Bandgap

G. Theodorou et al., “Structural, electronic, and optical properties of strained SiGe alloys,” Phys Rev B, vo.l 50, pp. 18355-18359, 15 Dec. 1994.

0.6

0.7

0.8

0.9

1

1.1

1.2

0 0.2 0.4 0.6 0.8 1

Ge fraction, x

Si1-xGex

Si Ge

90 K

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Outline

• The Team and Coordination

• Goals & Applications

• Technical Objectives & Approach

> SiGe Cryo Power HBTs

• SiGe Cryo Power Converters

• Summary & Plans

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~0.5 μm n+ Si

~0.4 μm p SiGe

~20 μm n– Si

Emitter contact

~150 μm n+ Si

Collector contact

Base contact

Cryo Power HBT Design Example

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A Cryo Power HBT Die

~4 mm

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Cryo Power HBT Characteristics

20 V

RT

2 A

20 V

1 A

LN

IB = 5 mA

Gain ~ 75

IB = 0.5 mA

Gain ~ 500

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Cryo Power HBT Characteristics

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Outline

• The Team and Coordination

• Goals & Applications

• Technical Objectives & Approach

• SiGe Cryo Power HBTs

> SiGe Cryo Power Converters

• Summary and Plans

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SiGe Boost Converter Circuit

Outputcapacitor

SiGe diode

Switching pulse

Inductor

LoadSiGe HBT

+

–

Inputcapacitor

24 V in 48 V out

~10 – 300 K

Drivecircuit

Power supply

+

–

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SiGe 100 W Cryo Boost Converter100 kHz, 24 V in, 48 V out

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SiGe 100 W Cryo Boost ConverterBackside

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LHe vendor’s dewar

LHe

~ 4”

Cu thermal mass/mounting block

SuperinsulationCooling channel(inside Cu block)

Stainless steel tubesGHe vent

Electrical feedthru

~ 8”

Converter circuitry

Cryostat for Measuring 100 W Circuits(variable temperature 300 to ~20 K)

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Cryostat for Measuring 100 W Circuits

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100 W SiGe Power Converter in Cryostat

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SiGe 100 W Cryo Boost Converter Performance

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Outline

• The Team and Coordination

• Goals & Applications

• Technical Objectives & Approach

• SiGe Cryo Power HBTs

• SiGe Cryo Power Converters

> Summary & Plans

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Summary

• Cryogenic power conversion is of interest for a range of applications within NASA and elsewhere.

• For cryogenic power conversion, SiGe devices are potentially superior to devices based on Si or Ge.

• We have begun development of SiGe semiconductor devices (HBTs and MOSFETs) for cryogenic power applications.

• We have designed, fabricated, and used SiGe HBTs in power converters operating at cryogenic temperatures and converting >100 W.

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Plans• Improve SiGe HBT characteristics (especially at cryo temps)

– By simulation– On voltage– Off breakdown voltage– Switching speed

• Compare power converter performance at cryogenic

temperatures, comparing SiGe HBTs to Si BJTs

• Design, fabricate and use SiGe MOSFETs in cryogenic

power circuits

• If practical, fabricate SiGe IGBTs