LITHOGRAPHICALLY PATTERNED COBALT

MICROSTRUCTURES AND ITS CHARACTERISTICSRAJEEV R. PILLAI

 Register No: 071605100010M.Tech Nano Technology

Biotechnology Centre, Department of Nano TechnologyAnna University

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INTRODUCTIONSpintronics LaboratoryIndian Institute of ScienceBangalore Guide

Dr. P. S. Anil KumarAssistant Professor

Department of Physics

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Thin Film

• Thin material layers ranging from fractions of a nanometer to several micrometers in thickness.

• Mechanical strength• Carrier

transportation• Super conducting

transitions• Magnetic properties• Optical Properties

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Applications

• Electrical Conductor films

• Optical films• Decorative films• Wear resistant

coating• Corrosion

resistant films• Dry film lubricants• Magnetic films for

recording

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Thin Film deposition process

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PROJECT

• FABRICATION OF COBALT MICROSTRUCTURE

• &• CHARECTERISATION

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Desired Microstructure

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Attractiveness of Cobalt Thin Film

• It is Ferro magnetic in nature• Apt for spin-based studies• Research areas includes

spintronics, leading to higher capacity memory devices

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Process Involved

• DC Magnetron Sputtering• Direct Laser beam writing• Ion Beam etching• Atomic Force Microscopy• MR Measurements

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DC Magnetron Sputtering

It consist of the following:1. Vacuum system

Vacuum chambers

Vacuum pumps

Load Lock

Spherical

Cylindrical

Rotary Pump

TSP

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Experimental Set Up – Cont…

2. Control Unit3. Pressure Gauges4. Transporter Rod5. Targets6. Gas System7. Thickness Monitor8. Substrate (Silicon)

Pirani

Micro Ion

Argon

Nitrogen

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DC Magnetron sputtering

Advantages– Lower voltage

needed to strike plasma.

– Controls uniformity.

– Reduce wafer heating from electron bombardment.

– Increased deposition rate

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Sputtering Unit at IIsc

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Direct Laser Beam Writing

•Spin Coating•Pre-baking•Laser Writing•Developing•Post-baking

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Ion Beam etchingBase Pressure 3.6E-6mbar (250 Hz)

Pressure with Argon = 2.6E-4mbar (183 Hz)

Cathode filament current 3.19A

Beam Voltage 400V

Acceleration Voltage 200V

Neutraliser filament current 2.79A

Discharge Voltage 38V

Discharge current = 0.16A

Neutraliser emission current 16mA

Beam current = 9mA

Acceleration current 1mA

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Atomic Force Microscopy

• Non – contact mode• Approach • Advanced• Height Profile• 3D scanning

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MR Measurements

1. The sample is placed on a glass slide and connections are made on the contact pads in the structure using copper wires

2. The wires are attached to the sample using silver paste.

3. The sample is now loaded on sample holder and connections are made

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4. The sample holder is loaded into the vacuum chamber and using a rotary pump the chamber is evacuated.

5. The four connections are labeled as: 1---I+

2--I-

3---V-

4---V+

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6. Load the vacuum chamber (with sample inside) in between electromagnets

7. Power the electromagnets and give 300 Oe magnetic field to the sample and a constant current of 1m A is applied to it

8. Now switch ON the lab view software system display on the computer and set the number of scans =10 and the average time for each scan as 5min

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9. The magnetic field and electric field are parallel to each other and the angle between them is 0(deg)

10. Now increase the magnetic field values and record the change in resistance of the sample using the scanning lab view software.

11. Similarly do the scanning for the different angles starting from 0 to 360.

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12. Plot the different data points in the scanned data using origin graph software.

13. Now calculate the %MR (magneto resistance) values for each angle from the scan plot.

14. Finally plot a graph between angle between the magnetic field and electric current () and the %MR obtained for each value of () using origin software.

15. Thus AMR of the Cobalt microstructure can be observed from the graph.

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RESULTS: Co target - before & after sputtering

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Cobalt microstructure

Cobalt microstructure

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Result & Conclusion

• A thin film of cobalt was deposited on a silicon substrate by DC magnetron sputtering technique and a microstructure of cobalt with our desired dimensions was fabricated on this thin film using Direct laser beam technique followed by ion beam etching. The microstructure’s structural characterization was done by optical and atomic force microscopy.

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• Finally, its magnetoresistive properties were studied and its resistance was found to be varying with the angle between magnetic field and current and have maximum values of MR when both the current and magnetic field are in same direction confirming it to be showing AMR.

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