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3D Sensor Characterization, Electrode Capacitance Measurements. Martin Hoeferkamp , Sally Seidel, Igor Gorelov University of New Mexico 8 th RD50 Workshop, Prague 27 June 2006. Introduction. - PowerPoint PPT Presentation
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Martin Hoeferkamp,UNM
3D Sensor Characterization,Electrode Capacitance Measurements
Martin Hoeferkamp, Sally Seidel, Igor GorelovUniversity of New Mexico
8th RD50 Workshop, Prague27 June 2006
Martin Hoeferkamp,UNM2
Introduction
• Motivation: a need for 3D sensors to have an electrode capacitance compatible in value with existing front end chip requirements.
• Eg. , ATLAS Pixel detector upgrade, 3D sensors on TOTEM experiment will use ATLAS front end chip.
• Measured values on the order of 100fF, difficult with LCR meter• An alternative method of capacitance measurement is presented.
• 3D sensors received from Sherwood Parker (Hawaii U.) and Chris Kenney (Stanford U.) include:- non-irradiated sensor- irradiated 3D sensors– 2x1014 cm-2 55 MeV proton– 1x1015 cm-2 55 MeV proton
Martin Hoeferkamp,UNM3
3D Sensor Configuration• Configuration of Measured Devices
– Alternating columns of n- and p-electrodes– Most electrodes are connected together along each column– Some electrodes are left isolated, to be contacted and measured individually
• Top view layout • Layout dimensions( not same as ATLAS pixel)
Martin Hoeferkamp,UNM4
Electrode Capacitance, direct meas.• Direct Measurement uses standard CV measurement with LCR meter (HP4284A)
• Irrad 1015 55MeVp: N Electrode • Non-irradiated: N Electrode
• Irrad 2x1014 55MeVp: N ElectrodeResult: very low electrode capacitanceCnon-irrad N ~ 59fF(10KHz), 38fF(100KHz),
32fF(1MHz)Cirrad 2x1014 N ~ 72fF(10KHz), 72fF(100KHz),
62fF(1MHz)Cirrad 1x1015 N ~ 91fF(10KHz), 80fF(100KHz),
60fF(1MHz)
Martin Hoeferkamp,UNM5
Electrode Capacitance, direct meas.• Direct Measurement using LCR meter (HP4284A)
• Irradiated 1015 55MeVp: P Electrode • Non-irradiated: P Electrode
• Irradiated 2x1014 55MeVp: P Electrode
Result: very low electrode capacitanceCnon-irrad P ~ 71fF(10KHz), 58fF(100KHz),
46fF(1MHz)Cirrad 2x1014 P ~ 96fF(10KHz), 69fF(100KHz),
53fF(1MHz)Cirrad 1x1015 P ~ 98fF(10KHz), 70fF(100KHz),
55fF(1MHz)
Martin Hoeferkamp,UNM6
Electrode Capacitance, direct meas.• Direct Measurement using LCR meter (HP4284A)• Non-irradiated: N Electrode
Result: electrode capacitance decreases with lower temperature, and reaches a minimum value at ~ -10oC.
Martin Hoeferkamp,UNM7
Electrode Capacitance, direct meas.• Dependence of CV characteristics on measurement frequency
• The frequency dependence is observed at every temperature.
• Frequency dependence of irradiated sensors is due to the finite reaction time of the deep traps which respond better to lower frequency signals (Lancaster U.).
• The capacitances are higher for more heavily irradiated sensors
• There is a temperature dependence of the capacitance at a fixed measurement frequency.
• Capacitance depends on the frequency and the temperature, same as for planar sensors.
Martin Hoeferkamp,UNM8
Electrode Capacitance, indirect meas.
• Indirect Measurement using Decay Time of IR pulse on an isolated electrode.• Electrode is grounded through input impedance of a Picoprobe 35.• The IR laser induced charge is collected, rising signal on measured pulse.• When the laser is turned off the signal decay follows an exponential with a time
constant = R*(C+C3D) , referred to here as RC time constant.
• C3D is extracted from the decay time constant using values of probe resistance and capacitance.
PICOPROBE 35
R=1.25M
C=.05pF
To Oscilloscope
Pulsed1064nm IR Laser +Vbias
Gnd
Martin Hoeferkamp,UNM9
Electrode Capacitance, indirect meas.
• Laser: 1064 nm EG&G• Probes: Picoprobe 35 26GHz BW, Cascade Microtech coaxial• Oscilloscope: Tektronix TDS7254 2.5Ghz BW• Thermal Chuck: Micromanipulator (-60oC )
Vbias
PICOPROBE 35
R=1.25M
C=.05pF
Fast Pulser
OscilloscopeFocused Laser1064nm
Thermal Chuck
Martin Hoeferkamp,UNM10
Electrode Capacitance, indirect meas.• Indirect Measurement using Decay Time Picoprobe 35 signal, Non-irradiated p-electrode
Non-irradiated 3D PElectrode Decay, PP 35 Decay
0
0.05
0.1
0.15
0.2
0.E+00 1.E-07 2.E-07 3.E-07 4.E-07 5.E-07 6.E-07 7.E-07 8.E-07
Time (Sec)
Pu
lse
He
igh
t (A
U)
• RC Time Const = R*(C+C3d)= 169nS
• C3D = 85fF
Non-irradiated 3D PElectrode Decay, PP 35 Decay
y = 0.393995e-5939838.327796x
R2 = 0.9974080.001
0.01
0.1
1
0.E+00 1.E-07 2.E-07 3.E-07 4.E-07 5.E-07 6.E-07 7.E-07 8.E-07
Time (Sec)
Pu
lse
Hei
gh
t (A
U)
Martin Hoeferkamp,UNM11
Electrode Capacitance, indirect meas.• Indirect Measurement using Decay Time of signal on Picoprobe,• Non-irradiated p-electrode• Average RC time constant is 169nS, p-electrode capacitance is 85fF
Decay Curves, 3D sensor Non-irradiated
00.020.040.060.08
0.10.120.140.160.18
0.2
0.E+00 2.E-07 4.E-07 6.E-07 8.E-07
Bias Voltage (V)
Pu
lse
he
igh
t (A
U)
60V,tau=173nS
50V,tau=174nS
40V,tau=172nS
30V,tau=171nS
20V,tau=168nS
15V,tau=167nS
12V,tau=164nS
10V,tau=165nS
8V,tau=157nS
6V,tau=149nS
2V,tau=132nS
0V,tau=316nS
Capacitance, Non-irradiated 3D sensor
0
20
40
60
80
100
0 10 20 30 40 50 60
Bias Voltage (V)
Ca
pa
cit
an
ce
(fF
)
Martin Hoeferkamp,UNM12
Electrode Capacitance, indirect meas.• Indirect Measurement using Decay Time of signal on Picoprobe 35, Irradiated sensor p-electrode
Irradiated 2x1014 cm-2 55MeVp, 3D P Electrode
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.00 200.00 400.00 600.00 800.00 1000.00
Time (nS)
Pu
lse
He
igh
t (m
V)
* On irradiated sensors there is a long tail at longer times which may be due to release of charge from traps produced by irradiation.
• Assuming a single dominant trapping time constant :
V = [Vo-Vo(RC/-RC)]e-t/RC + Vo(RC/-RC)]e-t
(Ref: S. Parker and C. Kenney, IEEE Trans. Nuc. Sci. ,Vol. 48, No. 5, Oct. 2001)
Irradiated 2x1014 cm-2 55MeVp, PP35 Decay
y = 0.09042668e-0.00490353x
R2 = 0.98572507
0.001
0.01
0.1
0.00 200.00 400.00 600.00 800.00 1000.00
Time (nS)
Pu
lse
He
igh
t (m
V)
Martin Hoeferkamp,UNM13
Electrode Capacitance, indirect meas.• Indirect Measurement using Decay Time of signal on Picoprobe 35, Irradiated sensor p-electrode
Time Const=R*(C+C3d)=177nS,C3D=91.6fF Second time const = 273nS
Irradiated 2x1014 cm-2 55MeVp, PP35 Decay
y = 0.11378952e-0.00565837x
R2 = 0.99611865
0.001
0.01
0.1
0.00 100.00 200.00 300.00 400.00 500.00 600.00
Time (mS)
Pu
lse
He
igh
t (m
V)
Irradiated 2x1014 cm-2 55MeVp, PP35 Decay
y = 0.03901790e-0.00359994x
R2 = 0.99303441
0.001
0.01
0.1
500.00 550.00 600.00 650.00 700.00 750.00 800.00 850.00
Time (nS)
Pu
lse
He
igh
t (m
V)
Irradiated 2x1014 cm-2 55MeVp, 3D P Electrode
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.00 200.00 400.00 600.00 800.00 1000.00
Time (nS)
Pu
lse
He
igh
t (m
V)
Irradiated 2x1014 cm-2 55MeVp, PP35 Decay
y = 0.09042668e-0.00490353x
R2 = 0.98572507
0.001
0.01
0.1
0.00 200.00 400.00 600.00 800.00 1000.00
Time (nS)
Pu
lse
He
igh
t (m
V)
Martin Hoeferkamp,UNM14
Electrode Capacitance, indirect meas.
• Indirect Measurement using Decay Time of signal on Picoprobe• Irradiated 2x1014 cm-2 55MeVp sensor p-electrode• Average RC time constant is 177nS, p-electrode capacitance is 91.6fF• Second (trapping?) time constant is 273nS
Decay Curves, 3D sensor irrad 2x1014 55MeVp
0
0.05
0.1
0.15
0.2
0.25
0.E+00 1.E-07 2.E-07 3.E-07 4.E-07 5.E-07
Time (S)
Pu
lse
he
igh
t (A
U)
100V, tau=177nS
90V,tau=176.5nS
80V,tau=177nS
70V,tau=177nS
60V,tau=177.4nS
50V,tau=183.5nS
40V,tau=198nS
30V,tau=198nS
20V,tau=207nS
10V,tau=231nS
0V,tau=252nS
Capacitance, 3d Irrad 2x1014 cm-2 55MeVp
020406080
100120140160180
0 20 40 60 80 100
Bias Voltage (V)C
apac
itan
ce (
fF)
Martin Hoeferkamp,UNM15
Electrode Capacitance, indirect meas.• Indirect Measurement using Decay Time of signal on Picoprobe• Irradiated 1x1015 cm-2 55MeVp sensor p-electrode• Average RC time constant is 247nS, p-electrode capacitance is 147fF• Second (trapping?) time constant is 373nS
Capacitance, 3d Irrad 1x1015 cm-2 55MeVp
0
50
100
150
200
250
0 20 40 60 80 100 120
Bias Voltage (V)
Cap
acit
ance
(fF
)
Decay Curves, 3D sensor Irrad 1x1015cm-2 55MeVp
00.005
0.010.015
0.020.025
0.030.035
0.040.045
0.05
0.E+00 1.E-07 2.E-07 3.E-07 4.E-07
Bias Voltage (V)
Pu
lse
he
igh
t (A
U)
130V,tau=249.5nS
120V,tau=250nS
110V,tau=252nS
100V,tau=247nS
90Vtau=245nS
80V,tau=248nS
70V,tau=242nS
60V,tau=211nS
50V,tau=240nS
30V,tau=240nS
20V,tau=218nS
10V,tau=220nS
Martin Hoeferkamp,UNM16
Electrode Capacitance, calculation
• 3D Electrostatic Calculation (IES Coulomb):– P Electrode Length = 120 um– P Electrode Diameter = 20 um– Center electrode to nearest neighbors
Result: 3D calculation C3D P electrode = 31fFNote: result verified by S. Watts (Brunel U.) using an alternative calculation.
n n
n n
p p p
Martin Hoeferkamp,UNM17
Comparison of Results• Summary: Indirect measurement gives similar results to 10KHz LCR meter result
Non-Irrad Irrad 2x1014 Irrad 1x1015
LCR meter 10KHz, P electrode 71 fF 96 fF 98 fF
LCR meter 100KHz, P electrode 58 fF 69 fF 70 fF
LCR meter 1MHz, P electrode 46 fF 53 fF 55 fF
Indirect Measurement, P electrode 85 fF 92 fF 147 fF
3D calculation, P electrode 31 fF
Martin Hoeferkamp,UNM18
Summary• Two methods for measuring 3D sensor capacitance and results are
presented.
• In general the indirect method gives similar results to the direct method with the LCR meter frequency of 10KHz. This is also consistent with the RD50 guideline of 10KHz LCR measurements.
• 3D sensor Electrode Capacitance depends on frequency of the LCR meter and on the sensor temperature, same as for planar sensors.
• Need to further investigate possibility of extracting the trapping time constant from the second time constant of the irradiated sensors.
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