FABRICATION, CALIBRATION AND

CHARACTERIZATION OF MICRO-SCALE

RESISTANCE TEMPERATURE

DETECTORS(RTD’s)

KUNJAN CHAUDHARI

AdvisorDr. Hyejin MoonCommittee MembersDr. Hyejin MoonDr. Miguel AmayaDr. Donghyun Shin

IMNfL

INTEGRATED MICRO/NANOFLUIDICs LAB

OUTLINE2

• Introduction

– Resistance Temperature Detector and its features.

• Motivation

• Experimental details

– Design of RTD

– Experimental Setup

– LabVIEW Setup with flowchart

• Indium Tin Oxide

– Fabrication

– Literature Review

– Conclusion and Results

• Nickel

– Fabrication

– Results

– Conclusions

• Conclusions

• Future work

RESISTANCE TEMPERATURE

DETECTOR• Resistance Temperature Detectors are temperature sensors that contain a resistor

that changes resistance value as its temperature changes.

• Many conductive materials change resistance with the change in temperature.

• Common RTD sensing elements have a repeatable resistance versus temperaturerelationship (R vs T) and operating temperature range.

R=Rref[1+α(T-Tref)]Where,R= Resistance at temperature “T”.Rref= Resistance at reference temperature (usually 21˚C)α=Temperature Co-efficient of Resistivity for the sensor.T=Unknown Temperature to be measured.Tref=Reference Temperature taken (21˚C).

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Thin Film RTD

Wire wound RTD

FEATURES OF RTD

Applications• Air conditioning and

refrigeration • Food Processing• Textile production• Petrochemical processing• Micro electronics• Air, gas and liquid

temperature measurement.• Laboratory temperature

measurements.• Temperature measurements

in Aircrafts .• Medical devices.• Microfluidics.

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When to use RTD?• For accuracy and stability requirements.• For accuracy over a wide temperature range.• When immunity to electrical noise is desired. • For a high degree of standardization.

Advantages • Linearity over wide operating range• High temperature operating range• Repeatability.• Good stability at high temperature.• Accuracy

MOTIVATION

• Resistive Temperature Detectors were used by Shreyas for measuring temperature of Droplet in his study of Digital EWOD.

• Indium Tin Oxide provides optical transparency.• Ease of integration in microfluidic devices .• Ease in fabrication .• Suitable material for EWOD patterning (electrodes).

EWOD

Electrode

RTD

HeaterCredit: Shreyas

Bindiganavale, PhD

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Credit:

Shreyas Bindiganavale, PhD

ITO Resistance vs Temperature Curve

GOALS OF RESEARCH

• Fabrication ,calibration and characterization of micro-scale resistance temperaturedetector (RTD) for measuring temperature at micro level.

• Structural change in material due to Heat treatment and its effect on theperformance of RTD.

• Identifying the limitation of RTD.

• Create a final Recipe for fabrication of RTD’s in EWOD platforms.

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RTD DESIGN

Thickness of RTD material:

1. ITO= 200 nm

2. Nickel = 100 nm

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RTD Design

Our substrate is Glass with 700µm thickness.

Side view of Device

RTD/Heater on glass substrate

Glass Substrate

RTD material

EXPERIMENTAL SETUP• Heat Source – Fisher Scientific ISOTEMP Hot Plate.

• Data measurement – Agilent 34980A Data Acquisition System.

• Software – NI LabVIEW 2015.

• Temperature measurement – Thermocouples (‘K’ type , ‘J’ type).

• Connecting Wires – Copper wires.

• Device – Clean room fabricated – ITO RTD and Nickel RTD.

• Oil used-Valvoline SAE 0W-20.

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K-type Thermocouple

Schematic of the Experimental setup

Thermocouple 3

Thermocouple 1

Thermocouple 2

OIL BATH

DAQ

Computer with LabVIEW

Container with InsulationHOT PLATE

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• Oil Bath calibration Technique for calibration of RTD.

– For steady state temperature.

– To maintain uniformity of temperature on entire surface of RTD.

– Better temperature control.

– Inertness to the materials.

• Advantages of motor oil

– Relatively High boiling point.(300˚C).

– For Calibration at higher ranges of temperatures.

– The value for Thermal Time Constant is very small.

– Commercially available.

OIL BATH CALIBRATION

www.popularmechanics.com

EXPERIMENTAL SETUP

System for Data Acquisition Agilent 34980A

Hot Plate

Oil Bath with Hot Plate

Computer with LabVIEW

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FLOWCHART OF CALIBRATION

ThermocouplesRTD

INITIALIZING CONFIGURE MEASUREMENT

MEASURING OUTPUT TO DISPLAY

DATA ACQUISITION HARDWARE

OIL BATH

Timed Loop

LABVIEW PROGRAM

DATA ACQUISITION SYSTEM

Ref. Temperature for Thermocouples

4-Wire Resistance Measurement

Graphs

Numeric

Activation of DAQ

Arrangement of channels

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LABVIEW PROGRAM

Credit: LABVIEW

INITIALIZE VI

Configure Measurement VI

Measurement VI

Output VI

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INDIUM TIN OXIDE• Indium tin oxide is a mixture of indium(III) oxide (In2O3) and tin(IV) oxide

(SnO2), typically 90% In2O3, 10% SnO2 by weight.

• An electrode having good conductivity.

• Provides optical transparency.

• Ease in fabrication and patterning.

• Thin films are deposited on surfaces by physical vapor deposition, electronbeam deposition or a range of sputter deposition techniques.

• Applications in LCD, OLED, plasma screen , touch screens, aircraft windshields ,Photovoltaic Solar Cells , Electron Circuitry.

Credit : INDIUM CORPORATIONCredit : www.adafruit.com

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ITO CLEAN ROOM FABRICATION

ITO Heater/RTD fabrication

1)

2)

3)

4)

5)

GLASS SUBSTRATE

ITO

HMDS

PHOTORESIST

Spin Coating HMDS and PR

Lithography and Developing

ITO etching

PR Stripping

Magnified Resistance Path

Fabricated ITO RTD/Heater

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LITERATURE REVIEWHiroshi Morikawa , M. Fujita, Crystallization and electrical property change on the annealing of amorphous indium-oxide and indium-tin-oxide thin films, Thin Solid Films 359 (1999) 61-67.Hiroshi Morikawa ,H . Sumi , M. Kohyama , Crystal growth of ITO films prepared by DC magnetron sputtering on C film , Thin Solid Films 281-282 (1996) 202

Credit: H. Morikawa et. al

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• H. Morikawa et al. investigated the behavior of ITO filmson substrate.

• The film is almost amorphous including a small amountof nuclei, most of which are generated directly on thesubstrate surface during deposition.

• Observed that ITO changes its crystal structure whensubjected to high temperatures.

• Decrease in Resistivity because of increase in carrier concentration supplied by Sn atoms which became active at high temperatures.

ANNEALED ITO (2 HOURS at 200˚C)

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CONCLUSION FROM THE EXPERIMENTS

• Partial Crystallization of ITO after 2 hours of Annealing.

• Non-linear Temperature v/s Resistance Curve.

• Multiple tests didn’t give repeatable results.

• Increasing the Annealing time may fully crystallize the ITO grain structure.

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Credit: H. Morikawa,M. Fujita

a)at 150˚C,b)at 210˚C ,c)at 240˚C

LITERATURE REVIEW

• Paine et al. observed ITO thin film usingTEM technique and found that as-deposited ITO film has a fully amorphousstructure.

• After annealing in air at 162 °C, the samplebecomes crystalline consisting of largeblock-like grains that are, on average,approximately 100 nm in size.

• The Resistivity of the material changesbecause of relaxation of distorted bonds inthe as-deposited amorphous material.

Credit: David C Paine et el.

Credit: David C Paine et el.

Credit: Paine et.al, A study of low temperature crystallization of amorphous thin film indium-tin-oxide , J Appl. Phys. , Vol. 85,No. 12,15 June 1999

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ANNEALED ITO (8 HOURS at 200˚C)

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CONCLUSION FROM EXPERIMENTS

• No considerable change observed after increasing the time of Annealing.

• Partial Crystallization of ITO.

• Non-linear Temperature vs Resistance Curve.

• Multiple tests didn’t give repeatable results.

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LITERATURE REVIEW

• K.L. Fang et.al observed that after annealing at 150˚C for the ITO sample givesrelatively very less change in its resistivity.

• U.Betz et.al in their research concluded that :

- At 150 °C the thermal activation induces the structural relaxation mechanism, resultingin an initial decrease of the resistivity value.

- Crystallization process begins at 150 °C.

Credit: U. Betz et al

Credit: K. L. Fang et al

• Credits: U. Betz et.al, Thin films engineering of indium tin oxide: Large area flat panel displays application, Surface & Coatings Technology 200(2006) 5751-5759

• Credits: K.L. Fang et.al , Low Temperature Crystallization of Indium-tin-oxide

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NON-ANNEALED ITO RTD22

RESISTANCE V/S TEMPERATURE CURVE

FOR ITO

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THIN FILM NICKEL

• Well known material of choice for RTD construction.

• Have a known and linear positive Temperature v/s resistance characteristics under 300˚C.

• Cost-effective and remains stable in harsh oxidizing environment.

• A good compromise between copper and platinum.

• Ease in fabrication.

Credit : www.heraeus.comCredit: www.William-Rowland.com

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NICKEL CLEAN ROOM FABRICATION

• Piranha Solution cleaning prior to deposition

• Nickel was also encapsulated with a layer of Di-electric.

• Anneal at 200˚C for two hours2)

3)

4)

5)

6)

GLASS SUBSTRATENICKEL

HMDSPHOTORESIST

Spin Coating HMDS and PR

Lithography and Developing

Nickel etching

PR Stripping

E-Beam Deposition1)

7)

Su-8 layerSu-8 spin coating

Nickel RTD fabrication

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Fabricated Nickle RTD

NICKEL RTD/HEATERS

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RESISTANCE v/s TEMPERATURE PLOT FOR

NICKEL RTD

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RESULTS AND CONCLUSIONS

Annealing

Conditions

Nature of Plot Repeatable Resistivity(ρ)(in Ω-

cm)

TCR

(/˚C)

Operating

Temperature

ITO

2 Hours @

200˚C

Non-linear No 2.3*10^-4 N/A N/A

8 Hours @

200˚C

Non-linear No 2.3*10^-4 N/A N/A

Non-annealed Linear Yes 2.3*10^-4 0.0007 22˚C-150˚C

Nickel 2 Hours @ 200˚C Linear Yes 6.11*10^-6 0.004 22˚C-200˚C

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• Indium Tin Oxide can be used as Resistive Temperature Detector under the temperature range of 150˚C when it is Amorphous in nature.

• Annealing plays an important role in changing the state from amorphous to crystalline.

• Nickel can be used as RTD for a greater range of temperatures after Annealing and using a passivation layer.

FUTURE WORK

• Studying of behavior of ITO with different deposition technique.

• Calibrating ITO RTD for Very High Temperatures.

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REFERENCES

• [1] Hiroshi Morikowa, M. Fujita, Crystallization and electrical property change on the annealing of amorphous indium-oxide and indium-tin-oxide thin films, Thin Solid Films 359 (1999) 61-67.

• [2] Hiroshi Morikawa ,H . Sumi , M. Kohyama , Crystal growth of ITO films prepared by DC magnetron sputtering on C film , Thin Solid Films 281-282 (1996) 202

• [3]U. Betz et.al, Thin films engineering of indium tin oxide: Large area flat panel displays application, Surface & Coatings Technology 200(2006) 5751-5759

• [4]Paine et.al, A study of low temperature crystallization of amorphous thin film indium-tin-oxide , J Appl. Phys. , Vol. 85,No. 12,15 June 1999

• [5] K.L. Fang et.al , Low Temperature Crystallization of Indium-tin-oxide

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ACKNOWLEDGEMENT

• I would like to thank Dr. Hyejin Moon, for providing me opportunity , investing her valuable time in training me and for her encouragement throughout this research thesis.

• I would also like to thank Arvind Venkatesan, Ali Farzbod , Shubhodeep Paul and MunMun Nahar for guiding and supporting me throughout the research study.

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QUESTIONS?

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