motivation experimental conditions

Characterization of irradiated MOS-C with X-rays using CV-measurements

and gated diode techniques

Q. Wei, L. Andricek, H-G. Moser, R. H. Richter,

Max-Planck-Institute for Physics Semiconductor Laboratory

• Motivation• Experimental conditions • Study of the radiation damage by CV-

measurements and gated diode technique, annealing behavior at RT, comparison of extracted Nox, Nit values

• Discussion of the results

Outline

• Radiation damage of semiconductor devices (e.g. DEPFET)

• Study on the radiation damage with MOS-C using CaliFa teststand at MPI HLL Munich

• Comparison of results from two different measurement methods (MOS-C and gated diode)

Motivation

Comparison between different semiconductor devices

MOS-C Gated diode DEPFETNox

(method)

ΔVFB

(CV-Measurement)

∆VFB & ∆Vg

(CV-Measurement & gated diode technique)

Δ Vt

(IV-Measurement)

Nit

(method)

Stretchout (High-low

frequency based on the CV)

Full width at 2/3 maximal of current

(gated diode technique)

Subthreshold slope

(Subthreshold technique)

Other parameters

S0, σn/p &

(gated diode technique)

gm

(IV-Measurement)

(Only for the 1-D defects)

0

• Irradiation: X-Ray tube with Mo target at 30kV and 30mA (17,44keV & Bremsstrahlung ) dose: 1 week of irradiation up to 1M rad, dose rate: 2.5rad/s (1rad=0.01J/kg)• Samples:

– Based on n-type high resistance silicon(450m) wafer: doping concentraion ~ 1012 cm-3

• Bias conditions: +5V,0V,-5V for MOS-C; 0V for gated diode• Measurements:

– CV: HF (10kHz); LF (20Hz) all values in series mode (Cs, Rs)

– Gated diode: VAl: 10V, Vedge: 0.25V, VAl/Poly: from positive to negative values– Annealing: at RT for about 5 days on MOS-C and 10 days on Gated Diode

Experimental Conditions

Substrate

Substrate

Poly1/Poly2 AluminiumLTO

Oxide

Ni

Cross section and layout of MOS-C

Poly1/2

Al

–MOS-C: –the upper left – Al1–the upper right – Al2–the lower left –Poly1–the lower right –Poly2–each contact area is about 10 mm2

Al2

For MOS-C

extracted results for MOS-C & Gated Diode

CV-Al(LF)

0.00E+00

1.00E-10

2.00E-10

3.00E-10

4.00E-10

5.00E-10

6.00E-10

7.00E-10

8.00E-10

9.00E-10

-60 -50 -40 -30 -20 -10 0 10

Vgate (V)

C (F

)

0krad

4.5krad

13.5krad

22.5krad

36krad63krad

189krad

225krad

382.5krad423krad

1003.5krad

CV-Al(HF)

0.00E+00

1.00E-10

2.00E-10

3.00E-10

4.00E-10

5.00E-10

6.00E-10

7.00E-10

8.00E-10

9.00E-10

-50 -40 -30 -20 -10 0 10

Vgate (V)

C (F

)

0 rad

4.5krad

13.5krad

22.5krad

36krad

63krad

189krad

225krad

382.5krad

423krad

1003.5krad

CV-Poly1(HF)

0.00E+00

2.00E-10

4.00E-10

6.00E-10

8.00E-10

1.00E-09

1.20E-09

1.40E-09

1.60E-09

1.80E-09

-13 -8 -3 2 7

Vgate (V)

C (F

)

0krad

4.5krad

13.5krad

22.5krad

36krad

63krad

189krad

225krad

382.5krad

423krad

1003.5krad

CV-Poly1(LF)

0.00E+00

2.00E-10

4.00E-10

6.00E-10

8.00E-10

1.00E-09

1.20E-09

1.40E-09

1.60E-09

1.80E-09

-14 -9 -4 1 6

Vgate (V)

C (F

)

0krad4.5krad

13.5krad

22.5krad

36krad

63krad

189krad

225krad

382.5krad

423krad

1003.5krad

CV-Measurement Gate Bias conditions: 0V

Al/Poly1/2-Ox-It

0.000E+00

2.000E+11

4.000E+11

6.000E+11

8.000E+11

1.000E+12

1.200E+12

1.400E+12

1.600E+12

0 200 400 600 800 1000Dose(krad)

Nit

& N

ox (c

m-2

)

Al-ox

Poly1-Ox

Poly2-Ox

Al-it

Poly1-it

Poly2-it

CV-Poly2(HF)

0.00E+00

2.00E-10

4.00E-10

6.00E-10

8.00E-10

1.00E-09

1.20E-09

1.40E-09

1.60E-09

1.80E-09

-12 -7 -2 3 8

Vgate (V)

C (F

)0krad

4.5krad

13.5krad

22.5krad

36krad

63krad

189krad

225krad

382.5krad

423krad

1003.5krad

CV-Poly2(LF)

0.00E+00

2.00E-10

4.00E-10

6.00E-10

8.00E-10

1.00E-09

1.20E-09

1.40E-09

1.60E-09

1.80E-09

-13 -8 -3 2 7

Vgate (V)

C (F

)

0krad

4.5krad

13.5krad

22.5krad

36krad

63krad

189krad

225krad

382.5krad

423krad1003.5krad

For MOS-C

Flat band voltage Shift Nox

high-low frequency CV

Nit

CV-Measurement Gate Bias conditions: 0V

Annealing for MOS-C Gate bias conditions: 0V

10000 1000001.40E+012

1.50E+012

1.60E+012

1.70E+012

1.80E+012

1.90E+012

2.00E+012

yscale(Y) = A + B * xscale(X)where scale() is the current axis scale function.

Parameter Value Error------------------------------------------------------------A 3.05658E12 5.47588E10B -2.84185E11 1.08554E10------------------------------------------------------------

R SD N P-------------------------------------------------------------0.99637 1.75366E10 7 <0.0001

measurement data linear fit of data

Nox

(cm

-2)

Time (s)

Annealing-Al

10000 100000

6.80E+011

6.90E+011

7.00E+011

7.10E+011

7.20E+011

7.30E+011

7.40E+011



R SD N P-------------------------------------------------------------0.97228 4.74391E9 7 2.42096E-4

Nox

(cm

-2)

Time (s)


Annealing-Poly2

10000 1000006.20E+011

6.30E+011

6.40E+011

6.50E+011

6.60E+011

6.70E+011



R SD N P-------------------------------------------------------------0.99183 2.30303E9 7 <0.0001

Nox

(cm

-2)

Time (s)


Annealing-Poly1

During annealing Nox decreases linearly with ln(t)

Weak annealing

(~25%)

(~6,5%)

(~6,5%)

pos itive oxid charge

0.0E+00

5.0E+11

1.0E+12

1.5E+12

2.0E+12

2.5E+12

3.0E+12

3.5E+12

4.0E+12

0 50 100 150 200

Dose (Krad)

Nox

(cm

-2)

Al

Po1

Po2

Inte rface Trap

0.0E+00

1.0E+11

2.0E+11

3.0E+11

4.0E+11

5.0E+11

6.0E+11

0 50 100 150 200

Dos e (Krad)

Nit

(cm

-2)

Al

Po1

Po2

For MOS-C

Due to too large leakage current

at dose 200krad

CV-Measurement does not work

Gate bias conditions: +5V

literatur:

Interface trap will not saturate

at dose of 1Mrad!

Gate bias conditions: -5VFor MOS-Cpositive oxid charge

0.0E+00

2.0E+11

4.0E+11

6.0E+11

8.0E+11

1.0E+12

1.2E+12

1.4E+12

1.6E+12

0 100 200 300 400 500 600 700 800 900 1000

Dose (krad)

Nox

(cm

-2)

Al

Po1

Po2

Interface Trap

0.0E+00

1.0E+11

2.0E+11

3.0E+11

4.0E+11

5.0E+11

6.0E+11

7.0E+11

0 100 200 300 400 500 600 700 800 900 1000

Dose (krad)

Nit

(cm

-2)

Al

Po1

Po2

For MOS-C positive oxide charge

0.0E+00

5.0E+11

1.0E+12

1.5E+12

2.0E+12

2.5E+12

3.0E+12

3.5E+12

4.0E+12

0 200 400 600 800 1000dose (krad)

Nox

(cm

-2)

Al/+5V

poly/+5V

Al/0V

poly/0V

Al/-5V

poly/-5VMuch more defects (Nox,Nit)

for positive gate than for 0V bias both poly-gate and Al-

gate structure

More defects for Al-gate than poly-gate

Almost the same amount of defects (Nox,Nit) for negative

gate bias as for 0V both poly-gate and Al-gate structure

interface trap

0.0E+00

1.0E+11

2.0E+11

3.0E+11

4.0E+11

5.0E+11

6.0E+11

7.0E+11

0 200 400 600 800 1000

dose (krad)

Nit

(cm

-2)

Al/+5V

Poly/+5V

Al/0V

poly/0V

Al/-5V

poly/-5V

VG at +5V Vs. VG at 0V

VG at -5V Vs. VG at 0V

For any given VG

Cross section structure and layout for gated diode

P+

Al/PolyGa

te

AAl

Substrate

V

Edge

N

VErde

5µm95µm

Poly-gateAl-gate

Al

P+

grounding

Edge

Al

P+

•gated diode wafer•the left one – Al•the right one –poly•each area is 9 mm2

Al

-2.20E-08

-1.70E-08

-1.20E-08

-7.00E-09

-2.00E-09

-37 -32 -27 -22 -17 -12 -7 -2 3

V poly (V)

I pdi

ode

(A)

Vor Bestr.

nach 189 krad Bes tr.

al nach 360 kradBes tr.al nach 963 kradBes tr.

For gated Diode

Poly

-3.40E-08

-2.90E-08

-2.40E-08

-1.90E-08

-1.40E-08

-9.00E-09

-4.00E-09

-15 -13 -11 -9 -7 -5 -3 -1 1 3 5

V poly (V)

I pdi

od (A

)

vor Bes tr.

nach 189 krad Bes tr.

poly nach 360krad Bes tr.

poly nach 963krad Bes tr.

Radiation damage

0.000E+00

1.000E+11

2.000E+11

3.000E+11

4.000E+11

5.000E+11

6.000E+11

0 100 200 300 400 500 600 700 800 900 1000

dose(krad)

Nox

& N

it(cm

-2)

Qox-Al

Qox-Poly

Qit-AlQit-Polypeak shift Nox

Full width at 2/3 Imax Nit

By using gated diode technique Gate bias conditions: 0V?

Poly-CV(HF)

0.00E+00

2.00E-10

4.00E-10

6.00E-10

8.00E-10

1.00E-09

1.20E-09

1.40E-09

-23 -18 -13 -8 -3 2 7

Vgate (V)

C (F

)

poly vor Bestr.

poly nach 189krad

poly nach 360krad

poly nach 963krad

Al-CV(HF)

0.00E+00

1.00E-10

2.00E-10

3.00E-10

4.00E-10

5.00E-10

6.00E-10

7.00E-10

-25 -20 -15 -10 -5 0 5

Vgate (V)

C (F

)

al vor Bestr.

al nach 189krad

al nach 360krad

al nach 963krad

Using CV-method (HF)

For gated Diode Gate bias conditions: 0V

A good agreement for determination of Nox by ΔVFB(CV) and ΔVG(gated diode technique)

Annealing for Gated DiodePoly Annealing

-4.50E-08

-4.00E-08

-3.50E-08

-3.00E-08

-2.50E-08

-2.00E-08

-1.50E-08

-1.00E-08

-5.00E-09

0.00E+00

-8 -7.5 -7 -6.5 -6 -5.5 -5 -4.5 -4

V poly (V)

Igen

(A)

poly direkt nach Bestr.

poly nach 2 Std. Ann.


poly nach 24.5 Std. Ann.





Al Aannealing

-2.40E-08

-1.90E-08

-1.40E-08

-9.00E-09

-4.00E-09

1.00E-09

-33 -28 -23 -18 -13

V al (V)

Igen

(A)

al direkt nach Bestr.

al nach 2 Std. Ann.

al nach 7 Std. Ann.

al nach 24.5 Std. Ann.


al nach 68 Std. Ann.



10000 100000 1000000

4.90E+011

5.00E+011

5.10E+011

5.20E+011

5.30E+011

5.40E+011

5.50E+011

5.60E+011



R SD N P-------------------------------------------------------------0.94605 7.39859E9 7 0.00126------------------------------------------------------------

Qox

(cm

-2)

time (s)

Annealing--Al

10000 100000 10000004.90E+011

5.00E+011

5.10E+011

5.20E+011

5.30E+011

5.40E+011

5.50E+011

5.60E+011

5.70E+011



R SD N P-------------------------------------------------------------0.94864 7.94354E9 7 0.00112------------------------------------------------------------

Qox

(cm

-2)

time(s)

Annealing--Poly

During annealing Nox decreases linearly with ln(t)

Weak annealing

Using gate controlled diode technique

Small fraction of positive oxide charges (~11%) are recoverd!

Gate bias conditions: 0V

Surface generation velosity

0,0E+00

2,0E+01

4,0E+01

6,0E+01

8,0E+01

1,0E+02

1,2E+02

1,4E+02

1,6E+02

0 100 200 300 400 500 600 700 800 900 1000

dose (krad)

So (c

m/s

)

Al

poly

surface generation lifetime

0.000E+00

5.000E+03

1.000E+04

1.500E+04

2.000E+04

2.500E+04

3.000E+04

3.500E+04

4.000E+04

4.500E+04

5.000E+04

0 100 200 300 400 500 600 700 800 900 1000

dose (krad)

tau

(mic

rose

cond

)

alpoly

capture cross section for electron

0.000E+00

5.000E-16

1.000E-15

1.500E-15

2.000E-15

2.500E-15

3.000E-15

0 100 200 300 400 500 600 700 800 900 1000

dose (krad)

sigm

a (c

m-2

)

alpoly

for Gated Diode

0

n

0S

Gate bias conditions: 0V

(due to another traps)

GSF – National Research Center for Environment and Health, Munich

60Co (1.17 MeV and 1.33 MeV)

"OFF"

"ON"

Bias during irradiaton:

1: empty int. gate, in „off“ state, VGS= 5V, VDrain=-5V Eox ≈ 02: empty int. gate, in „on“ state, VGS=-5V, VDrain=-5V Eox ≈ -250kV/cm3: all terminals at 0V

Results for DEPFET

1. postive oxide charge: negative shift of the theshold voltage (~tox2)

2. interface traps: higher 1/f noise and reduced mobility (gm)

No annealing during irradiation ~ 3 days irradiation

Radiation Effects (ionizing radiation)

Transconductance and subtreshold slope

s=85mV/dec

s=155mV/dec

Vth=-0.2V

Vth=-4.5V

Literature: After 1Mrad 200 nm (SiO2):

Nit ≈ 1013 cm-2

300 krad Nit≈2·1011 cm-2

912 krad Nit≈7·1011 cm-2

No change in the transconductance gm

)()10ln( 12 DDox

it SSkTCN

Discussion of the resultsComparison of Nox and Nit between MOS-C and gated diode

for Al- and poly-gate structure at dose of 189krad and 1Mrad

For Nox: a good agreement for poly-gate structure (MOS-C & gated diode)

For Al-gate structure: more Nit and Nox on MOS-C than on Gated diode

More Nit and Nox for Al-gate than poly-gate structure (MOS-C)

For Nox: the same for both Al-gate and poly-gate structure (Gated diode)

dose Nox MOS-C Gated diode

189krad Al 8,3e11 3,3e11

189krad Poly 3,3e11 2,6e11

dose Nit MOS-C Gated diode

189krad Al 2,8e11 5,1e10

189krad Poly 6e10 1,2e11

dose Nox MOS-C Gated diode

1Mrad Al 1,9e12 5,7e11

1Mrad Poly 6,7e11 5,7e11

dose Nit MOS-C Gated diode

1Mrad Al 6,8e11 1,2e11

1Mrad Poly 1,1e11 2,1e11

For poly-gate structure: more Nit on Gated diode than on MOS-C

For Nox: More Nit for poly-gate than Al-gate structure (Gated diode)

dose DEPFET Nox Nit

912krad Poly 6~7e11 7e11

For Nox: DEPFET=Gated diode MOS-C √

For Nit: DEPFET>Gated diode>MOS-C ?

(Poly-gate structure for three devices)

≈

≈

≈

≈

Comparison between literature and our experiment

• Differences for the saturation effect of interface trap on MOS-C

• Differences for the generation of defects on MOS-C (poly-gate for DEPFET)

• Differences for defect generation at negative gate bias on MOS-C

T.P. Ma, P. DressendorferJohn Wiley&Sons,1989.

Winokur, 1985. Derbenwick, Gregory, 1975

Backup slides

Performance before irradiation

55Fe

Energy (eV)

Coun

ts/

chan

nel

o non-irrad. double pixel DEPFETo L=7μm, W=25 μm

o Vthresh≈-0.2V, Vgate=-1V

o Idrain=41 μA

o Drain current read out

o time cont. shaping =6 μs

Noise ENC=2.3 e- (rms)

at T>23 degC

Non-irradiated:


Performance after irradiation for DEPFET

55Fe

Energy (eV)

Cou

nts/

chan

nel

o Irradiated double pixel DEPFETo L=7μm, W=25 μmo after 913 krad, 60Co

o Vthresh≈-4V, Vgate=-5.3V

o Idrain=21 μA

o Drain current read out

o time cont. shaping =6 μs


at T>23 degC

motivation experimental conditions

Documents

layout of mos

gated diode techniques

gated diodecomparison

gated diodemeasurements

rsgated diode

week of irradiation

dose rate

nit values discussion