3D Sensor Characterization, Electrode Capacitance Measurements
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Transcript of 3D Sensor Characterization, Electrode Capacitance Measurements
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.