comparison of pr-iv-cv for pzt capacitor...uf/cm^2, ua/cm^2, uf/cm^2 sw cv10 nsw cv10 sw iv*2.5...

Radiant Technologies, Inc.Comparing PV, IV, and CV

Comparison of the RemanentPolarization, IV, and Small

Signal CV for a PZT CapacitorRadiant Technologies, Inc.

August 12, 2010ISAF-ECAPD ‘10


Summary• It is possible to measure the remanent polarization curve, the IV, and

the small signal CV of a capacitor in addition to its normal polarizationhysteresis.– Small signal and large signal piezoelectric displacement are next.

• The IV response and small signal CV response of a ferroelectriccapacitor seem to be modulated by the remanent polarization state ofthe capacitor.

• Comparison of the remanent polarization, the IV, and the small signalCV of a single PZT capacitor with platinum electrodes indicates thatthat leakage is a direct function of remanent polarization but the smallsignal CV has a more complex relationship to the remanentpolarization.


Capacitor under Test• 0.26µ 20/80 PZT

• Platinumelectrodes

• TiOx/SiOx ILD

• Chrome/Goldmetallization

• 3.0V saturation

• Can withstandlong exposures to9V.

100,000 µ2 Pt/PZT/Pt CapacitorContact Pad in Gold

PZT


Packaging• Two capacitors to each package• A shared common plus an independent connection for the other side of

each capacitor.• The package header and lid are connected together electrically and then

to the system ground at the socket to provide a shielded enclosure forthe devices when inserted into a tester or TO-18 socket board.

• TO-18 headers exhibit <0.5pF parasitic capacitance.

Top view

COMMON CAP A

CAP B CASECap A Cap BCommon

TO-18 Can


Test Fixture• The test data were collected from a single “AB” capacitor mounted

on the TO-18 Socket Board shown below.

Cap A

Cap B

Common

GND


Test Procedure• The test procedure consisted of the following tests in order:

– Three polarization vs voltage measurements:→ +4V 1 second hysteresis loop→ -4V 1 second hysteresis loop→ ±4V 1 second remanent hysteresis loop

– Two small signal capacitance vs voltage tests to ±4V using 1 kHzsignal:→ Switching→ Nonswitching

– Two current vs voltage tests to ±4V using 1 second integration:→ Switching→ Nonswitching


Remanent Hysteresis• The PUND test is a familiar measurement:

• Any matched pair of switched and non-switched pulses may besubtracted from each other to get the remanent polarization.

Drive Voltage

Time

PresetPulse

DelayPeriod

±Vmax

PositiveSwitched

Pulse

PositiveUnswitched

Pulse

NegativeSwitched

Pulse

NegativeUnswitched

Pulse


Remanent Hysteresis• The same measurement may be made using half-hysteresis

loops instead of pulses:

• The difference between the switching and non-switching measurementswill give the Remanent Polarization vs Voltage function.

Switching Non-switching

1/2Period


Switching and Non-switching half loops:Switching & Non-switching Loops

0

10

20

30

40

50

60

70

0 1 2 3 4 5Volts

uC/v

m̂2

SwitchingNon-switching

Remanent Hysteresis


• PUND: P*r - P^r = dP = Qswitched• Hysteresis: Switching - Non-switching = Remanence:

Remanent Hysteresis Calculation

-10

0

10

20

30

40

50

60

70

0 1 2 3 4 5Volts

uC/v

m̂2

SwitchingDifferenceNon-Switching

RemanentHalf Loop

Remanent Hysteresis


• The test may be executed in both voltage directions and the two halvesjoined to show the switching of the remanent polarization that takesplace inside the full loop.

-30

-20

-10

0

10

20

30

-4 -3 -2 -1 0 1 2 3 4

Full Remanent Hysteresis Measurement Results[ Radiant AB WHITE ]

Pol

ariz

atio

n

Volts

Unswitched - Logic 0 Switched - Logic 1 Remanent

Remanent Hysteresis


• The first stage of the experiment consisted of measuring two 4Vhysteresis loops going in opposite directions (including their gaps) and a4V remanent polarization loop.

Remanent vs Normal Hysteresis

-30

-20

-10

0

10

20

30

-4 -3 -2 -1 0 1 2 3 4

1 Second Hyst vs 1 second Rhyst[ Radiant Type AB White, 9V preset ]

Pol

ariz

atio

n

Voltage

+4V 1s Rhyst: Polarization (µC/cm2) -4V 1s Hyst: Polarization (µC/cm2)

+4V 1s Hyst: Polarization (µC/cm2)

• The remanenthysteresis is in blue.

• The full loops inopposite directionsoverlay exactly.

• The Vc of theremanent loop liesoutside that of thenormal loops. Why?(Hint: the reason ispurely mathematical.)

• The Vc of theremanent loop is thetrue Vc.


• There are two tests in Vision that take data over a range of DC biasvalues:

– Small Signal Capacitance (the Advanced CV task)– IV

• Normally, a DC bias profile for these tests should look like the figurebelow:

DC Bias Tests

Stimulus

time


• Since there is the possibility that remanent polarization might affect theoutcome of these tests, both of these tasks provide a method by which the stateof the remanent polarization may be set prior to the beginning of both halves ofthe DC bias profile.

DC Bias Tests

Stimulus

time

Remanent polarization preset pulses.


• Using saturated polarization conditions, there are two possibilities!

• The trajectory of the tests shown above will check for “hysteresis” inthe IV and small signal CV measurements.

DC Bias Tests

Stimulus

time

Switching

Stimulus

time

Non-switching


• The test profiles below eliminate the hysteresis measurement and check themeasured properties only with increasing bias.

DC Bias Tests

Stimulus

time

Non-switching

Stimulus

time

Switching


• 1 kHz 0.2V test with 182 points

Non-switching CV Result

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-4 -3 -2 -1 0 1 2 3 4

Non-switching Small Signal CV[ Radiant Type AB WHITE ]

Nor

mal

ized

Cap

acita

nce

(µF/

cm2)

Voltage


• 1 kHz 0.2V test with 182 points

Switching CV Result

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-4 -3 -2 -1 0 1 2 3 4

Switching Small Signal CV[ Radiant Type AB WHITE ]

Nor

mal

ized

Cap

acita

nce

(µF/

cm2)

Voltage


Non-switching vs Switching CV

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-4 -3 -2 -1 0 1 2 3 4

1KHz SW vs nSW CV[ Radiant Type AB White, 9V preset ]

uF/c

m^2

Volts

1ms 4V CV nSW: Capacitance (nF) 1ms 4V CV SW: Capacitance (nF)


• 1 second integration time test with 182 points

Non-switching IV for the Sampleunder Test

0

1

2

3

4

5

6

7

8

-4 -3 -2 -1 0 1 2 3 4

1 Second 9V Unswitched IV[ Radiant Type AB White ]

Cur

rent

/Are

a (m

icro

Am

ps/c

m2)

Voltage


• 1 second integration time test with 182 points

Switching IV for the Sample underTest

0

1

2

3

4

5

6

7

8

-4 -3 -2 -1 0 1 2 3 4

1 Second 9V Switched IV[ Radiant Type AB White ]

Cur

rent

/Are

a (m

icro

Am

ps/c

m2)

Voltage


Non-switching vs Switching IV

SW vs nSW IV

01

23

45

67

-5 -3 -1 1 3 5

Volts

uA/c

m^2

SW IVnSW IV

0.26u 20/80 PZT with Pt electrodes.


• The IV values (µA/cm2) are multiplied by x2.5 to make them more visible.• The CV values (µF/cm2) are multiplied by x10 to make them more visible.

Compare PV, CV, & IV

Hysteresis Parameters

-40

-30

-20

-10

0

10

20

30

40

50

-6 -4 -2 0 2 4 6

Volts

uC/c

m^2

, uA

/cm

^2, u

F/cm

^2

Rhyst

SW CV*10

nSW CV*10

SW IV*2.5

nSW IV*2.5


• The IV values (µA/cm2) are multiplied by x2.5 to make them more visible.• The CV values (µF/cm2) are multiplied by x10 to make them more visible.

Compare nCV, CV, & IV

nCV Parameters

-5

0

5

10

15

20

25

30

35

40

-6 -4 -2 0 2 4 6Volts

uF/

cm^2

, uA

/cm

^2, u

F/cm

^2

SW CV*10

nSW CV*10

SW IV*2.5

nSW IV*2.5

RnCV/4


• The small signal leakage of the capacitor is a direct function of theremanent polarization with the highest leakage occurring at the coercivevoltage for the remanent polarization switching.

• The small signal CV function is not linearly related to the remanentpolarization switching function.

• The small signal CV function is completed in its “switching” before thecoercive voltage of the remanent polarization switching.

• The small signal CV function appears to be an inverted “butterfly loop”typical of displacement measurement of a ferroelectric piezoelectricmaterial.

– An AFM measurement of the film displacement could be executed tocompare the small signal capacitance with piezoelectric displacement.

Analysis


• The displacement curve was measured on a 0.8µ thick 4/20/80 PNZT film with platinumelectrodes. The capacitor was 25µx40µ and was measured with a Polytec LaserVibrometer.

• The small signal CV measurement came from the 0.26µ thick 20/80 PZT film used inthis presentation.

Compare ssCV to Displacement

• The displacementmeasurement wasdivided by anarbitrary factorand inverted toscale it with thesmall signalcapacitancemeasurement.


• The small signal capacitance versus voltage, current versus voltagecharacteristics, and remanent polarization versus voltage share anintriguing relationship when measured on the same capacitor.

• No model or theory explaining the relationship is provided by theauthor. Only the physical relationship of the properties is presented.

• The most interesting comparison will be of the following measurementsall made from the same location on the same capacitor:

– Small signal capacitance versus voltage– Current versus voltage– Remanent polarization versus voltage– Large signal piston displacement of the capacitor surface (butterfly loop)– Small signal piston displacement of the capacitor surface.– Dynamic PFM movie of domain switching at the location of the measurements.– Static PFM small signal piezoelectric constant.

Conclusion

comparison of pr-iv-cv for pzt capacitor...uf/cm^2, ua/cm^2, uf/cm^2 sw cv*10 nsw cv*10 sw iv*2.5...

Documents

comparison of pr-iv-cv for pzt capacitor...uf/cm^2, ua/cm^2, uf/cm^2 sw cv10 nsw cv10 sw iv*2.5...