SiGe Semiconductor Devices

for

Cryogenic Power Electronics

Electrochemical Society

Seventh International Symposium on Low Temperature Electronics

14 October 2003, Orlando, Florida

2

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

GPD Optoelectronics Corp., Salem, New Hampshire

O. Mueller

LTE–Low Temperature Electronics, Ballston Lake, New York

R. L. Patterson, J. E. Dickman

NASA Glenn Research Center, Cleveland, Ohio

A. Hammoud

QSS Group Inc., Cleveland, Ohio

Supported by NASA Glenn Research Center and ONR/DARPA

Why use SiGe?

4

Why SiGe Devices?

• Si-Based Circuits Demonstrated, but only > 77 K

• Standard Si Bipolar Devices Cease Operation < ~100 K

• Applications Require Operation < 77 K, to ~30 – 40 K

• Possible Materials for < 77 K are Ge and SiGe

5

Why SiGe Devices?

• SiGe Devices Can Operate to Lowest Cryogenic

Temperatures (~ 0 K)

• All Device Types – Diodes, Field-Effect Transistors,

Bipolar Transistors

• Highly Compatible with Si Processing

• Can Optimize Devices for Cryogenic Applications

by Selective Use of Ge, Si, SiGe

• SiGe Provides Additional Flexibility through

Band-Gap Engineering (% of Ge)

Development Program

7

Development Program

• Parameters

– Low power (~10 W) to medium power (~100 W)

– Temperature range 300 K to ~20 K

• Past

– Initial SiGe diodes fabricated

– Initial SiGe heterojunction bipolars (HBTs) fabricated

• Future

– MOSFETs (lateral, vertical)

– Power HBTs (vertical)

– IGBTs (lateral, vertical)

SiGe Cryo Power Diodes

9

SiGe Cryo Power Diodes - Design

(N+ implant)

P+ SiGe Metal

Metal

N+

N– Si epi

N+ Si

10

SiGe vs Si Power Diodes - Forward

0

20

40

60

80

100

I (mA)Ifor (mA) RTIf RT (mA)If (mA)

0 0.2 0.4 0.6 0.8 1 1.2

Si

Vfor

(V)

300 K

2ASiGe: 1A

11

SiGe vs Si Power Diodes - Forward

0

20

40

60

80

100

I (mA)Ifor (mA) LNIf LN (mA)If (mA)

0 0.2 0.4 0.6 0.8 1 1.2

Vfor

(V)

77 K

Si2ASiGe: 1A

12

SiGe Cryo Power Diodes - Forward Voltage

0

0.5

1

1.5

0.2 A0.2 A SiVf 0.2 AVf 0.2 A

Vf (0.2 A)Vf (0.2 A)Vf @ 0.2 A (V)

0 40 80 120 160 200 240 280 320

Temperature (K)

Ge commercial

SiGe

If = 0.2 A

SiGe

13

SiGe Cryo Power Diodes - Forward

14

SiGe Cryo Power Diodes - Forward

15

0

0.5

1

1.5

1 A lines1 A symbols1 A line Si1 A symbol SiVf 1 A

Vf 1 AVf (1 A)Vf (1 A)Vf @ 1 A (V)

0 40 80 120 160 200 240 280 320

Temperature (K)

Ge commercial

Si

If = 1 A

Ge

SiGe

SiGe Cryo Power Diodes - Forward Voltage

16

SiGe Cryo Power Diodes - Reverse

-0.02

0

0.02

0.04

0.06

0.08

0.1

-100 -80 -60 -40 -20 0 20 40

Voltage (V)

SiGe/SiDiodes300 K

17

SiGe Cryo Power Diodes - Reverse

-0.02

0

0.02

0.04

0.06

0.08

0.1

-100 -80 -60 -40 -20 0 20 40

Voltage (V)

SiGe/SiDiodes77 K

18

SiGe Cryo Power Diodes - Reverse Recovery

-4

-2

0

2

4

6

8

10

12

0.0 0.2 0.4 0.6 0.8 1.0

Dio

de

Cu

rren

t (A

)

Time (µs)

300 K

77 K

SiGe-1B

Silicon-Germanium Diode

19

SiGe Cryo Power Diodes - Reverse Recovery

-4

-2

0

2

4

6

8

10

12

0.0 0.2 0.4 0.6 0.8 1.0

Dio

de

Cu

rren

t (A

)

Time (µs)

300 K

77 K

GPD SiGe-2A

Silicon-Germanium Diode

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SiGe Cryo Power Diodes - Results

• N on P and P on N, single and double epi

• Measured to 77 K; operate to ~?? K

• Forward V less than Si at low – med forward I

• Imax ~> 10 A (300 – 77 K)

• Reverse breakdown V >100 V (300 – 77 K)

• Reverse recovery decreases at 77 K

SiGe Cryo Heterojunction Bipolar Transistors (HBTs)

22

SiGe Cryo Power HBTs - Design

~ 0.5 μm n+ Si

~ 0.4 μm p SiGe

~ 20 μm n– Si

Emitter contact

~ 300 μm n+ Si

Collector contact

Base contact

N-P-N (N+/P/N-/N+)

23

SiGe Cryo Power HBTs - 300 K

24

SiGe Cryo Power HBTs - 80 K

25

SiGe Cryo Power HBTs - 80 K

26

SiGe Cryo Power HBTs - 80 K

27

SiGe Cryo Power HBTs - 40 K

28

SiGe Cryo Power HBTs - 40 K

29

SiGe Cryo Power HBTs - Results

• Initial fabrication

• NPN

• Operate down to ~40 K

• Power ~5 W, limited by package

• I max ~> 0.4 A (300 – 40 K)

• V forward breakdown ~>30 V (300 – 40 K)

• Need improved contacts

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Cryo Power SiGe Devices - Plans

• HBTs

– Improve HBT contacts, extend operation to ~20 K

– Larger area, I max to 10 A (300 – 20 K)

– V forward breakdown >100 V (300 – 20 K)

– High-power cryogenic packaging

• Additional Devices

– MOSFETs

– IGBTs

– Medium power, 300 – 20 K operation

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Summary

• Cryogenic power electronics is needed

for spacecraft going to cold environments

and for space observatories

• Temperatures may be as low as ~30 – 40 K

• We are developing SiGe devices specifically

for cryogenic power applications

• We have made initial SiGe cryo power diodes

and HBTs

• We plan to improve the diode and HBT

characteristics and to develop MOSFETs and IGBTs