Doping-type Dependence of Damage in Si Diodes Exposed to X-ray, Proton, and He+

Irradiation

MURI Meeting - June 2007

M. Caussanel1, A. Canals2, S. K. Dixit3, M. J. Beck4, A. D. Touboul5, R. D. Schrimpf6, D. M. Fleetwood6, and

S. T. Pantelides41 - LP2A, Université de Perpignan Via Domitia, Perpignan, 66860, FRANCE 2 - TRAD, Labege, 31674, FRANCE 3 - Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, TN 37235, USA 4 - Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA 5 - LAIN-UMR CNRS 5011, Université Montpellier II, F-34095 Montpellier cedex 5, FRANCE 6 - Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN, 37235, USA

Work supported by the AFOSR MURI Program

Outline- Context- Samples & Experimental Set-up- Results and Discussion on - Lifetime measurements - I-V Characteristics- Summary

MURI Meeting - June 2007 2

Context: For more than 40 years n-Si ≠ p-Si under radiation (1/2)- 1962 & 1988: disparities after electron irradiation

from very low energy (a few 100 keV [1]) to high energy

[2]

1. H. Flicker et al., Phys. Rev., 128, p. 2557 (1962)

2. C. J. Dale et al., IEEE Trans. Nucl. Sci., 35, p. 1208 (1988)

MURI Meeting - June 2007 3

Context: For more than 40 years n-Si ≠ p-Si under radiation (2/2)

- n-Si/p-Si difference ∝ fraction of damage due to low-energy PKA [4]

3. G. P. Summers et al., IEEE Trans. Nucl. Sci., 40, p. 1372 (1993)

- 1993 [3]: for NIEL<1 keV cm2/g• in n-Si: Damage Coefficient ∝ NIEL• in p-Si: Damage Coefficient ∝ NIEL21974

1965

1990

4. J. R. Srour et al., IEEE Trans. Nucl. Sci., 50, p. 653 (2003)

MURI Meeting - June 2007 4

Experimental Description

Radiation Sample Type

Characterization

Type Dose/Fluence

Measurements Method

X-raysUp to 500 krad (SiO2) by steps

n+/p junctions (NA= 4×1016

cm-3 )

I-V Parameter Analyzer

1.8 MeV H+ From

5.5×1010

to 1013 cm-3

p+/n junctions

(ND= 2.7×1015 cm-3

)

Minority

carrier

lifetime

Open-Circuit Voltage Decay method (OCVD)

1.4 MeV He+

MURI Meeting - June 2007 5

Sample Structure - Top View(Sandia TA 629TDC)

MURI Meeting - June 2007 6

Sample Structure - Cross-Section

G1916A/W33 – includes 1100 C N2 Post gate anneal before poly-Si

MURI Meeting - June 2007 7

Sample Structure - Ion range

MURI Meeting - June 2007 8

Minority Carrier Lifetime Measurement Set-up

0.5

0.4

0.3

0.2

0.1

0.0

Volt

age (

V)

43210Time x10-3 (s)

p+/n Pre-irradiation 1012 H+/cm2

1013 H+/cm2

Method based on the Open-Circuit Voltage Decay method (OCVD)

Lifetime value is extracted from the linear part of the curve:

kTqdVdt

Vg removed

MURI Meeting - June 2007 9

Reliability of the OCVD method:Measured lifetime checked with literature data

Hole lifetime in n-Si (may be reduced by High-T post-ox anneal)

Source: IOFFE Institute

MURI Meeting - June 2007 10

Reliability of the OCVD method:Measured lifetime checked with literature data

Electron lifetime p-Si

Source: IOFFE Institute

MURI Meeting - June 2007 11

I-V Characteristics under X-ray Radiation

Evidence that carrier trapping occurs at certain surfaces within the sample.

➙ This sensitivity of the surface regions of these diodes to defect buildup is consistent with recent results obtained on VDMOSFETs [6]

6. J. A. Felix et al., IEEE Trans. Nucl. Sci., 52, p. 2378 (2005)

10-1

100

101

102

103

104

105

Post

/Pre

-irra

diat

ion

I-V ra

tio

1.21.00.80.60.40.20.0Bias (V)

010 krad 050 krad 100 krad 500 krad

Increasingdose

Series Resistance RegionIdeal Diode Region

p+/n

MURI Meeting - June 2007 12

0.5

0.4

0.3

0.2

0.1

0.0

Volta

ge (V

)

3210-1Time x10-3

(s)

Pre-irradiation 010 krad(SiO2) 050 krad(SiO2) 100 krad(SiO2) 500 krad(SiO2)

NB: Arrows indicate increasing doses.

n+/p p+/n

X-ray Irradiation Impact on the Voltage Drop across the Junction during Lifetime Measurement

The voltage drop across the sample is reduced after the X-ray irradiation :- the higher the dose, the higher the reduction.- n+/p reduction > p+/n reduction.

➙ Also evidence of trapped charge at a SiO2/Si interface

MURI Meeting - June 2007 13

Ion Irradiation Impact on the Voltage Drop across the Junction during Lifetime Measurement

-0.20

-0.15

-0.10

-0.05

0.00

Volta

ge D

rop

Redu

ctio

n (V)

1010 1011 1012 1013 1014

Fluence (H+/cm -2)

n+/p junction p+/n junction

- Like X-rays, ion irradiation lowers the closed-circuit voltage drop across the sample.

➙ trapped charge within bulk- p+/n reduction > n+/p reduction

➙ this trend is opposite to X-ray radiationConsistent with recent theoretical work [5], which demonstrated that Frenkel pairs are generally more stable in p-Si than in n-Si.(Frenkel pairs act as electron trap in n-Si)

5. M. J. Beck et al., IEEE Trans. Nucl. Sci., 53, p.

3621 (2006)

MURI Meeting - June 2007 14

Ion Irradiation Impact on Bulk Lifetime

Electron lifetime in p gets reduced more by both H+ & He+ irradiations than hole lifetime in n by a 2-3× factor

This is despite the n doping being ~ 13x lower than the p doping

-100

-80

-60

-40

-20

0

Lifet

ime

Redu

ctio

n %

1010 1012 1014

Fluence (He+/cm -2)

p+/n n+/p

He+ irradiation

-100

-80

-60

-40

-20

0

Lifet

ime

Redu

ctio

n %

1010 1012 1014

Fluence (H+/cm -2)

p+/n n+/p

H+ irradiation

MURI Meeting - June 2007 15

Summary

- Surface trapping: n+/p more sensitive than p+/n

- Bulk trapping: n+/p less sensitive than p+/n

- Agreement with recent experiments and theory

X-ray, H+ and He+ irradiation of n+/p and p+/n diodes (I-

V & lifetime measurements)